diff --git a/Documentation/vm/00-INDEX b/Documentation/vm/00-INDEX index 11d3d8dcb..5269998fe 100644 --- a/Documentation/vm/00-INDEX +++ b/Documentation/vm/00-INDEX @@ -20,6 +20,8 @@ idle_page_tracking.txt - description of the idle page tracking feature. ksm.txt - how to use the Kernel Samepage Merging feature. +uksm.txt + - Introduction to Ultra KSM numa - information about NUMA specific code in the Linux vm. numa_memory_policy.txt diff --git a/Documentation/vm/uksm.txt b/Documentation/vm/uksm.txt new file mode 100644 index 000000000..be19a3127 --- /dev/null +++ b/Documentation/vm/uksm.txt @@ -0,0 +1,61 @@ +The Ultra Kernel Samepage Merging feature +---------------------------------------------- +/* + * Ultra KSM. Copyright (C) 2011-2012 Nai Xia + * + * This is an improvement upon KSM. Some basic data structures and routines + * are borrowed from ksm.c . + * + * Its new features: + * 1. Full system scan: + * It automatically scans all user processes' anonymous VMAs. Kernel-user + * interaction to submit a memory area to KSM is no longer needed. + * + * 2. Rich area detection: + * It automatically detects rich areas containing abundant duplicated + * pages based. Rich areas are given a full scan speed. Poor areas are + * sampled at a reasonable speed with very low CPU consumption. + * + * 3. Ultra Per-page scan speed improvement: + * A new hash algorithm is proposed. As a result, on a machine with + * Core(TM)2 Quad Q9300 CPU in 32-bit mode and 800MHZ DDR2 main memory, it + * can scan memory areas that does not contain duplicated pages at speed of + * 627MB/sec ~ 2445MB/sec and can merge duplicated areas at speed of + * 477MB/sec ~ 923MB/sec. + * + * 4. Thrashing area avoidance: + * Thrashing area(an VMA that has frequent Ksm page break-out) can be + * filtered out. My benchmark shows it's more efficient than KSM's per-page + * hash value based volatile page detection. + * + * + * 5. Misc changes upon KSM: + * * It has a fully x86-opitmized memcmp dedicated for 4-byte-aligned page + * comparison. It's much faster than default C version on x86. + * * rmap_item now has an struct *page member to loosely cache a + * address-->page mapping, which reduces too much time-costly + * follow_page(). + * * The VMA creation/exit procedures are hooked to let the Ultra KSM know. + * * try_to_merge_two_pages() now can revert a pte if it fails. No break_ + * ksm is needed for this case. + * + * 6. Full Zero Page consideration(contributed by Figo Zhang) + * Now uksmd consider full zero pages as special pages and merge them to an + * special unswappable uksm zero page. + */ + +ChangeLog: + +2012-05-05 The creation of this Doc +2012-05-08 UKSM 0.1.1.1 libc crash bug fix, api clean up, doc clean up. +2012-05-28 UKSM 0.1.1.2 bug fix release +2012-06-26 UKSM 0.1.2-beta1 first beta release for 0.1.2 +2012-07-2 UKSM 0.1.2-beta2 +2012-07-10 UKSM 0.1.2-beta3 +2012-07-26 UKSM 0.1.2 Fine grained speed control, more scan optimization. +2012-10-13 UKSM 0.1.2.1 Bug fixes. +2012-12-31 UKSM 0.1.2.2 Minor bug fixes. +2014-07-02 UKSM 0.1.2.3 Fix a " __this_cpu_read() in preemptible bug". +2015-04-22 UKSM 0.1.2.4 Fix a race condition that can sometimes trigger anonying warnings. +2016-09-10 UKSM 0.1.2.5 Fix a bug in dedup ratio calculation. +2017-02-26 UKSM 0.1.2.6 Fix a bug in hugetlbpage handling and a race bug with page migration. diff --git a/fs/exec.c b/fs/exec.c index 7eb8d21bc..bcd4e80a7 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -62,6 +62,7 @@ #include #include #include +#include #include #include @@ -1374,6 +1375,7 @@ void setup_new_exec(struct linux_binprm * bprm) /* An exec changes our domain. We are no longer part of the thread group */ current->self_exec_id++; + flush_signal_handlers(current, 0); } EXPORT_SYMBOL(setup_new_exec); diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c index 6bb20f864..3208972b4 100644 --- a/fs/proc/meminfo.c +++ b/fs/proc/meminfo.c @@ -118,6 +118,10 @@ static int meminfo_proc_show(struct seq_file *m, void *v) global_zone_page_state(NR_KERNEL_STACK_KB)); show_val_kb(m, "PageTables: ", global_zone_page_state(NR_PAGETABLE)); +#ifdef CONFIG_UKSM + show_val_kb(m, "KsmZeroPages: ", + global_zone_page_state(NR_UKSM_ZERO_PAGES)); +#endif #ifdef CONFIG_QUICKLIST show_val_kb(m, "Quicklists: ", quicklist_total_size()); #endif diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index bfbb44a5a..8dcd7f167 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -781,12 +781,25 @@ extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn, extern void untrack_pfn_moved(struct vm_area_struct *vma); #endif +#ifdef CONFIG_UKSM +static inline int is_uksm_zero_pfn(unsigned long pfn) +{ + extern unsigned long uksm_zero_pfn; + return pfn == uksm_zero_pfn; +} +#else +static inline int is_uksm_zero_pfn(unsigned long pfn) +{ + return 0; +} +#endif + #ifdef __HAVE_COLOR_ZERO_PAGE static inline int is_zero_pfn(unsigned long pfn) { extern unsigned long zero_pfn; unsigned long offset_from_zero_pfn = pfn - zero_pfn; - return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT); + return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT) || is_uksm_zero_pfn(pfn); } #define my_zero_pfn(addr) page_to_pfn(ZERO_PAGE(addr)) @@ -795,7 +808,7 @@ static inline int is_zero_pfn(unsigned long pfn) static inline int is_zero_pfn(unsigned long pfn) { extern unsigned long zero_pfn; - return pfn == zero_pfn; + return (pfn == zero_pfn) || (is_uksm_zero_pfn(pfn)); } static inline unsigned long my_zero_pfn(unsigned long addr) diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 44368b19b..0ae04f09f 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -21,21 +21,6 @@ struct mem_cgroup; #ifdef CONFIG_KSM int ksm_madvise(struct vm_area_struct *vma, unsigned long start, unsigned long end, int advice, unsigned long *vm_flags); -int __ksm_enter(struct mm_struct *mm); -void __ksm_exit(struct mm_struct *mm); - -static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) -{ - if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) - return __ksm_enter(mm); - return 0; -} - -static inline void ksm_exit(struct mm_struct *mm) -{ - if (test_bit(MMF_VM_MERGEABLE, &mm->flags)) - __ksm_exit(mm); -} static inline struct stable_node *page_stable_node(struct page *page) { @@ -65,6 +50,33 @@ struct page *ksm_might_need_to_copy(struct page *page, void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc); void ksm_migrate_page(struct page *newpage, struct page *oldpage); +#ifdef CONFIG_KSM_LEGACY +int __ksm_enter(struct mm_struct *mm); +void __ksm_exit(struct mm_struct *mm); +static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) +{ + if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) + return __ksm_enter(mm); + return 0; +} + +static inline void ksm_exit(struct mm_struct *mm) +{ + if (test_bit(MMF_VM_MERGEABLE, &mm->flags)) + __ksm_exit(mm); +} + +#elif defined(CONFIG_UKSM) +static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) +{ + return 0; +} + +static inline void ksm_exit(struct mm_struct *mm) +{ +} +#endif /* !CONFIG_UKSM */ + #else /* !CONFIG_KSM */ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) @@ -106,4 +118,6 @@ static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage) #endif /* CONFIG_MMU */ #endif /* !CONFIG_KSM */ +#include + #endif /* __LINUX_KSM_H */ diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index fd1af6b95..8387d696d 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -333,6 +333,9 @@ struct vm_area_struct { struct mempolicy *vm_policy; /* NUMA policy for the VMA */ #endif struct vm_userfaultfd_ctx vm_userfaultfd_ctx; +#ifdef CONFIG_UKSM + struct vma_slot *uksm_vma_slot; +#endif } __randomize_layout; struct core_thread { diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 7522a6987..58a55ff22 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -148,6 +148,9 @@ enum zone_stat_item { NR_ZSPAGES, /* allocated in zsmalloc */ #endif NR_FREE_CMA_PAGES, +#ifdef CONFIG_UKSM + NR_UKSM_ZERO_PAGES, +#endif NR_VM_ZONE_STAT_ITEMS }; enum node_stat_item { @@ -866,7 +869,7 @@ static inline int is_highmem_idx(enum zone_type idx) } /** - * is_highmem - helper function to quickly check if a struct zone is a + * is_highmem - helper function to quickly check if a struct zone is a * highmem zone or not. This is an attempt to keep references * to ZONE_{DMA/NORMAL/HIGHMEM/etc} in general code to a minimum. * @zone - pointer to struct zone variable diff --git a/include/linux/sradix-tree.h b/include/linux/sradix-tree.h new file mode 100644 index 000000000..d71edba6b --- /dev/null +++ b/include/linux/sradix-tree.h @@ -0,0 +1,77 @@ +#ifndef _LINUX_SRADIX_TREE_H +#define _LINUX_SRADIX_TREE_H + + +#define INIT_SRADIX_TREE(root, mask) \ +do { \ + (root)->height = 0; \ + (root)->gfp_mask = (mask); \ + (root)->rnode = NULL; \ +} while (0) + +#define ULONG_BITS (sizeof(unsigned long) * 8) +#define SRADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long)) +//#define SRADIX_TREE_MAP_SHIFT 6 +//#define SRADIX_TREE_MAP_SIZE (1UL << SRADIX_TREE_MAP_SHIFT) +//#define SRADIX_TREE_MAP_MASK (SRADIX_TREE_MAP_SIZE-1) + +struct sradix_tree_node { + unsigned int height; /* Height from the bottom */ + unsigned int count; + unsigned int fulls; /* Number of full sublevel trees */ + struct sradix_tree_node *parent; + void *stores[0]; +}; + +/* A simple radix tree implementation */ +struct sradix_tree_root { + unsigned int height; + struct sradix_tree_node *rnode; + + /* Where found to have available empty stores in its sublevels */ + struct sradix_tree_node *enter_node; + unsigned int shift; + unsigned int stores_size; + unsigned int mask; + unsigned long min; /* The first hole index */ + unsigned long num; + //unsigned long *height_to_maxindex; + + /* How the node is allocated and freed. */ + struct sradix_tree_node *(*alloc)(void); + void (*free)(struct sradix_tree_node *node); + + /* When a new node is added and removed */ + void (*extend)(struct sradix_tree_node *parent, struct sradix_tree_node *child); + void (*assign)(struct sradix_tree_node *node, unsigned int index, void *item); + void (*rm)(struct sradix_tree_node *node, unsigned int offset); +}; + +struct sradix_tree_path { + struct sradix_tree_node *node; + int offset; +}; + +static inline +void init_sradix_tree_root(struct sradix_tree_root *root, unsigned long shift) +{ + root->height = 0; + root->rnode = NULL; + root->shift = shift; + root->stores_size = 1UL << shift; + root->mask = root->stores_size - 1; +} + + +extern void *sradix_tree_next(struct sradix_tree_root *root, + struct sradix_tree_node *node, unsigned long index, + int (*iter)(void *, unsigned long)); + +extern int sradix_tree_enter(struct sradix_tree_root *root, void **item, int num); + +extern void sradix_tree_delete_from_leaf(struct sradix_tree_root *root, + struct sradix_tree_node *node, unsigned long index); + +extern void *sradix_tree_lookup(struct sradix_tree_root *root, unsigned long index); + +#endif /* _LINUX_SRADIX_TREE_H */ diff --git a/include/linux/uksm.h b/include/linux/uksm.h new file mode 100644 index 000000000..bb8651f53 --- /dev/null +++ b/include/linux/uksm.h @@ -0,0 +1,149 @@ +#ifndef __LINUX_UKSM_H +#define __LINUX_UKSM_H +/* + * Memory merging support. + * + * This code enables dynamic sharing of identical pages found in different + * memory areas, even if they are not shared by fork(). + */ + +/* if !CONFIG_UKSM this file should not be compiled at all. */ +#ifdef CONFIG_UKSM + +#include +#include +#include +#include +#include + +extern unsigned long zero_pfn __read_mostly; +extern unsigned long uksm_zero_pfn __read_mostly; +extern struct page *empty_uksm_zero_page; + +/* must be done before linked to mm */ +extern void uksm_vma_add_new(struct vm_area_struct *vma); +extern void uksm_remove_vma(struct vm_area_struct *vma); + +#define UKSM_SLOT_NEED_SORT (1 << 0) +#define UKSM_SLOT_NEED_RERAND (1 << 1) +#define UKSM_SLOT_SCANNED (1 << 2) /* It's scanned in this round */ +#define UKSM_SLOT_FUL_SCANNED (1 << 3) +#define UKSM_SLOT_IN_UKSM (1 << 4) + +struct vma_slot { + struct sradix_tree_node *snode; + unsigned long sindex; + + struct list_head slot_list; + unsigned long fully_scanned_round; + unsigned long dedup_num; + unsigned long pages_scanned; + unsigned long this_sampled; + unsigned long last_scanned; + unsigned long pages_to_scan; + struct scan_rung *rung; + struct page **rmap_list_pool; + unsigned int *pool_counts; + unsigned long pool_size; + struct vm_area_struct *vma; + struct mm_struct *mm; + unsigned long ctime_j; + unsigned long pages; + unsigned long flags; + unsigned long pages_cowed; /* pages cowed this round */ + unsigned long pages_merged; /* pages merged this round */ + unsigned long pages_bemerged; + + /* when it has page merged in this eval round */ + struct list_head dedup_list; +}; + +static inline void uksm_unmap_zero_page(pte_t pte) +{ + if (pte_pfn(pte) == uksm_zero_pfn) + __dec_zone_page_state(empty_uksm_zero_page, NR_UKSM_ZERO_PAGES); +} + +static inline void uksm_map_zero_page(pte_t pte) +{ + if (pte_pfn(pte) == uksm_zero_pfn) + __inc_zone_page_state(empty_uksm_zero_page, NR_UKSM_ZERO_PAGES); +} + +static inline void uksm_cow_page(struct vm_area_struct *vma, struct page *page) +{ + if (vma->uksm_vma_slot && PageKsm(page)) + vma->uksm_vma_slot->pages_cowed++; +} + +static inline void uksm_cow_pte(struct vm_area_struct *vma, pte_t pte) +{ + if (vma->uksm_vma_slot && pte_pfn(pte) == uksm_zero_pfn) + vma->uksm_vma_slot->pages_cowed++; +} + +static inline int uksm_flags_can_scan(unsigned long vm_flags) +{ +#ifdef VM_SAO + if (vm_flags & VM_SAO) + return 0; +#endif + + return !(vm_flags & (VM_PFNMAP | VM_IO | VM_DONTEXPAND | + VM_HUGETLB | VM_MIXEDMAP | VM_SHARED + | VM_MAYSHARE | VM_GROWSUP | VM_GROWSDOWN)); +} + +static inline void uksm_vm_flags_mod(unsigned long *vm_flags_p) +{ + if (uksm_flags_can_scan(*vm_flags_p)) + *vm_flags_p |= VM_MERGEABLE; +} + +/* + * Just a wrapper for BUG_ON for where ksm_zeropage must not be. TODO: it will + * be removed when uksm zero page patch is stable enough. + */ +static inline void uksm_bugon_zeropage(pte_t pte) +{ + BUG_ON(pte_pfn(pte) == uksm_zero_pfn); +} +#else +static inline void uksm_vma_add_new(struct vm_area_struct *vma) +{ +} + +static inline void uksm_remove_vma(struct vm_area_struct *vma) +{ +} + +static inline void uksm_unmap_zero_page(pte_t pte) +{ +} + +static inline void uksm_map_zero_page(pte_t pte) +{ +} + +static inline void uksm_cow_page(struct vm_area_struct *vma, struct page *page) +{ +} + +static inline void uksm_cow_pte(struct vm_area_struct *vma, pte_t pte) +{ +} + +static inline int uksm_flags_can_scan(unsigned long vm_flags) +{ + return 0; +} + +static inline void uksm_vm_flags_mod(unsigned long *vm_flags_p) +{ +} + +static inline void uksm_bugon_zeropage(pte_t pte) +{ +} +#endif /* !CONFIG_UKSM */ +#endif /* __LINUX_UKSM_H */ diff --git a/kernel/fork.c b/kernel/fork.c index e5d9d405a..6dec8b7ad 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -448,7 +448,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, goto fail_nomem; charge = len; } - tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); + tmp = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); if (!tmp) goto fail_nomem; *tmp = *mpnt; @@ -507,7 +507,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, __vma_link_rb(mm, tmp, rb_link, rb_parent); rb_link = &tmp->vm_rb.rb_right; rb_parent = &tmp->vm_rb; - + uksm_vma_add_new(tmp); mm->map_count++; if (!(tmp->vm_flags & VM_WIPEONFORK)) retval = copy_page_range(mm, oldmm, mpnt); diff --git a/lib/Makefile b/lib/Makefile index a90d4fcd7..3a3be2029 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -18,7 +18,7 @@ KCOV_INSTRUMENT_debugobjects.o := n KCOV_INSTRUMENT_dynamic_debug.o := n lib-y := ctype.o string.o vsprintf.o cmdline.o \ - rbtree.o radix-tree.o dump_stack.o timerqueue.o\ + rbtree.o radix-tree.o sradix-tree.o dump_stack.o timerqueue.o\ idr.o int_sqrt.o extable.o \ sha1.o chacha20.o irq_regs.o argv_split.o \ flex_proportions.o ratelimit.o show_mem.o \ diff --git a/lib/sradix-tree.c b/lib/sradix-tree.c new file mode 100644 index 000000000..ab21e6309 --- /dev/null +++ b/lib/sradix-tree.c @@ -0,0 +1,476 @@ +#include +#include +#include +#include +#include +#include +#include + +static inline int sradix_node_full(struct sradix_tree_root *root, struct sradix_tree_node *node) +{ + return node->fulls == root->stores_size || + (node->height == 1 && node->count == root->stores_size); +} + +/* + * Extend a sradix tree so it can store key @index. + */ +static int sradix_tree_extend(struct sradix_tree_root *root, unsigned long index) +{ + struct sradix_tree_node *node; + unsigned int height; + + if (unlikely(root->rnode == NULL)) { + if (!(node = root->alloc())) + return -ENOMEM; + + node->height = 1; + root->rnode = node; + root->height = 1; + } + + /* Figure out what the height should be. */ + height = root->height; + index >>= root->shift * height; + + while (index) { + index >>= root->shift; + height++; + } + + while (height > root->height) { + unsigned int newheight; + + if (!(node = root->alloc())) + return -ENOMEM; + + /* Increase the height. */ + node->stores[0] = root->rnode; + root->rnode->parent = node; + if (root->extend) + root->extend(node, root->rnode); + + newheight = root->height + 1; + node->height = newheight; + node->count = 1; + if (sradix_node_full(root, root->rnode)) + node->fulls = 1; + + root->rnode = node; + root->height = newheight; + } + + return 0; +} + +/* + * Search the next item from the current node, that is not NULL + * and can satify root->iter(). + */ +void *sradix_tree_next(struct sradix_tree_root *root, + struct sradix_tree_node *node, unsigned long index, + int (*iter)(void *item, unsigned long height)) +{ + unsigned long offset; + void *item; + + if (unlikely(node == NULL)) { + node = root->rnode; + for (offset = 0; offset < root->stores_size; offset++) { + item = node->stores[offset]; + if (item && (!iter || iter(item, node->height))) + break; + } + + if (unlikely(offset >= root->stores_size)) + return NULL; + + if (node->height == 1) + return item; + else + goto go_down; + } + + while (node) { + offset = (index & root->mask) + 1; + for (; offset < root->stores_size; offset++) { + item = node->stores[offset]; + if (item && (!iter || iter(item, node->height))) + break; + } + + if (offset < root->stores_size) + break; + + node = node->parent; + index >>= root->shift; + } + + if (!node) + return NULL; + + while (node->height > 1) { +go_down: + node = item; + for (offset = 0; offset < root->stores_size; offset++) { + item = node->stores[offset]; + if (item && (!iter || iter(item, node->height))) + break; + } + + if (unlikely(offset >= root->stores_size)) + return NULL; + } + + BUG_ON(offset > root->stores_size); + + return item; +} + +/* + * Blindly insert the item to the tree. Typically, we reuse the + * first empty store item. + */ +int sradix_tree_enter(struct sradix_tree_root *root, void **item, int num) +{ + unsigned long index; + unsigned int height; + struct sradix_tree_node *node, *tmp = NULL; + int offset, offset_saved; + void **store = NULL; + int error, i, j, shift; + +go_on: + index = root->min; + + if (root->enter_node && !sradix_node_full(root, root->enter_node)) { + node = root->enter_node; + BUG_ON((index >> (root->shift * root->height))); + } else { + node = root->rnode; + if (node == NULL || (index >> (root->shift * root->height)) + || sradix_node_full(root, node)) { + error = sradix_tree_extend(root, index); + if (error) + return error; + + node = root->rnode; + } + } + + + height = node->height; + shift = (height - 1) * root->shift; + offset = (index >> shift) & root->mask; + while (shift > 0) { + offset_saved = offset; + for (; offset < root->stores_size; offset++) { + store = &node->stores[offset]; + tmp = *store; + + if (!tmp || !sradix_node_full(root, tmp)) + break; + } + BUG_ON(offset >= root->stores_size); + + if (offset != offset_saved) { + index += (offset - offset_saved) << shift; + index &= ~((1UL << shift) - 1); + } + + if (!tmp) { + if (!(tmp = root->alloc())) + return -ENOMEM; + + tmp->height = shift / root->shift; + *store = tmp; + tmp->parent = node; + node->count++; +// if (root->extend) +// root->extend(node, tmp); + } + + node = tmp; + shift -= root->shift; + offset = (index >> shift) & root->mask; + } + + BUG_ON(node->height != 1); + + + store = &node->stores[offset]; + for (i = 0, j = 0; + j < root->stores_size - node->count && + i < root->stores_size - offset && j < num; i++) { + if (!store[i]) { + store[i] = item[j]; + if (root->assign) + root->assign(node, index + i, item[j]); + j++; + } + } + + node->count += j; + root->num += j; + num -= j; + + while (sradix_node_full(root, node)) { + node = node->parent; + if (!node) + break; + + node->fulls++; + } + + if (unlikely(!node)) { + /* All nodes are full */ + root->min = 1 << (root->height * root->shift); + root->enter_node = NULL; + } else { + root->min = index + i - 1; + root->min |= (1UL << (node->height - 1)) - 1; + root->min++; + root->enter_node = node; + } + + if (num) { + item += j; + goto go_on; + } + + return 0; +} + + +/** + * sradix_tree_shrink - shrink height of a sradix tree to minimal + * @root sradix tree root + * + */ +static inline void sradix_tree_shrink(struct sradix_tree_root *root) +{ + /* try to shrink tree height */ + while (root->height > 1) { + struct sradix_tree_node *to_free = root->rnode; + + /* + * The candidate node has more than one child, or its child + * is not at the leftmost store, we cannot shrink. + */ + if (to_free->count != 1 || !to_free->stores[0]) + break; + + root->rnode = to_free->stores[0]; + root->rnode->parent = NULL; + root->height--; + if (unlikely(root->enter_node == to_free)) + root->enter_node = NULL; + root->free(to_free); + } +} + +/* + * Del the item on the known leaf node and index + */ +void sradix_tree_delete_from_leaf(struct sradix_tree_root *root, + struct sradix_tree_node *node, unsigned long index) +{ + unsigned int offset; + struct sradix_tree_node *start, *end; + + BUG_ON(node->height != 1); + + start = node; + while (node && !(--node->count)) + node = node->parent; + + end = node; + if (!node) { + root->rnode = NULL; + root->height = 0; + root->min = 0; + root->num = 0; + root->enter_node = NULL; + } else { + offset = (index >> (root->shift * (node->height - 1))) & root->mask; + if (root->rm) + root->rm(node, offset); + node->stores[offset] = NULL; + root->num--; + if (root->min > index) { + root->min = index; + root->enter_node = node; + } + } + + if (start != end) { + do { + node = start; + start = start->parent; + if (unlikely(root->enter_node == node)) + root->enter_node = end; + root->free(node); + } while (start != end); + + /* + * Note that shrink may free "end", so enter_node still need to + * be checked inside. + */ + sradix_tree_shrink(root); + } else if (node->count == root->stores_size - 1) { + /* It WAS a full leaf node. Update the ancestors */ + node = node->parent; + while (node) { + node->fulls--; + if (node->fulls != root->stores_size - 1) + break; + + node = node->parent; + } + } +} + +void *sradix_tree_lookup(struct sradix_tree_root *root, unsigned long index) +{ + unsigned int height, offset; + struct sradix_tree_node *node; + int shift; + + node = root->rnode; + if (node == NULL || (index >> (root->shift * root->height))) + return NULL; + + height = root->height; + shift = (height - 1) * root->shift; + + do { + offset = (index >> shift) & root->mask; + node = node->stores[offset]; + if (!node) + return NULL; + + shift -= root->shift; + } while (shift >= 0); + + return node; +} + +/* + * Return the item if it exists, otherwise create it in place + * and return the created item. + */ +void *sradix_tree_lookup_create(struct sradix_tree_root *root, + unsigned long index, void *(*item_alloc)(void)) +{ + unsigned int height, offset; + struct sradix_tree_node *node, *tmp; + void *item; + int shift, error; + + if (root->rnode == NULL || (index >> (root->shift * root->height))) { + if (item_alloc) { + error = sradix_tree_extend(root, index); + if (error) + return NULL; + } else { + return NULL; + } + } + + node = root->rnode; + height = root->height; + shift = (height - 1) * root->shift; + + do { + offset = (index >> shift) & root->mask; + if (!node->stores[offset]) { + if (!(tmp = root->alloc())) + return NULL; + + tmp->height = shift / root->shift; + node->stores[offset] = tmp; + tmp->parent = node; + node->count++; + node = tmp; + } else { + node = node->stores[offset]; + } + + shift -= root->shift; + } while (shift > 0); + + BUG_ON(node->height != 1); + offset = index & root->mask; + if (node->stores[offset]) { + return node->stores[offset]; + } else if (item_alloc) { + if (!(item = item_alloc())) + return NULL; + + node->stores[offset] = item; + + /* + * NOTE: we do NOT call root->assign here, since this item is + * newly created by us having no meaning. Caller can call this + * if it's necessary to do so. + */ + + node->count++; + root->num++; + + while (sradix_node_full(root, node)) { + node = node->parent; + if (!node) + break; + + node->fulls++; + } + + if (unlikely(!node)) { + /* All nodes are full */ + root->min = 1 << (root->height * root->shift); + } else { + if (root->min == index) { + root->min |= (1UL << (node->height - 1)) - 1; + root->min++; + root->enter_node = node; + } + } + + return item; + } else { + return NULL; + } + +} + +int sradix_tree_delete(struct sradix_tree_root *root, unsigned long index) +{ + unsigned int height, offset; + struct sradix_tree_node *node; + int shift; + + node = root->rnode; + if (node == NULL || (index >> (root->shift * root->height))) + return -ENOENT; + + height = root->height; + shift = (height - 1) * root->shift; + + do { + offset = (index >> shift) & root->mask; + node = node->stores[offset]; + if (!node) + return -ENOENT; + + shift -= root->shift; + } while (shift > 0); + + offset = index & root->mask; + if (!node->stores[offset]) + return -ENOENT; + + sradix_tree_delete_from_leaf(root, node, index); + + return 0; +} diff --git a/mm/Kconfig b/mm/Kconfig index c782e8fb7..396522f2a 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -315,6 +315,32 @@ config KSM See Documentation/vm/ksm.txt for more information: KSM is inactive until a program has madvised that an area is MADV_MERGEABLE, and root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). +choice + prompt "Choose UKSM/KSM strategy" + default UKSM + depends on KSM + help + This option allows to select a UKSM/KSM stragety. + +config UKSM + bool "Ultra-KSM for page merging" + depends on KSM + help + UKSM is inspired by the Linux kernel project \u2014 KSM(Kernel Same + page Merging), but with a fundamentally rewritten core algorithm. With + an advanced algorithm, UKSM now can transparently scans all anonymously + mapped user space applications with an significantly improved scan speed + and CPU efficiency. Since KVM is friendly to KSM, KVM can also benefit from + UKSM. Now UKSM has its first stable release and first real world enterprise user. + For more information, please goto its project page. + (www.kerneldedup.org) + +config KSM_LEGACY + bool "Legacy KSM implementation" + depends on KSM + help + The legacy KSM implementation from Red Hat. +endchoice config DEFAULT_MMAP_MIN_ADDR int "Low address space to protect from user allocation" diff --git a/mm/Makefile b/mm/Makefile index e669f02c5..e2695e9a2 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -65,7 +65,8 @@ obj-$(CONFIG_SPARSEMEM) += sparse.o obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o obj-$(CONFIG_SLOB) += slob.o obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o -obj-$(CONFIG_KSM) += ksm.o +obj-$(CONFIG_KSM_LEGACY) += ksm.o +obj-$(CONFIG_UKSM) += uksm.o obj-$(CONFIG_PAGE_POISONING) += page_poison.o obj-$(CONFIG_SLAB) += slab.o obj-$(CONFIG_SLUB) += slub.o diff --git a/mm/memory.c b/mm/memory.c index 5fcfc2490..211a4ce99 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -128,6 +128,25 @@ EXPORT_SYMBOL(zero_pfn); unsigned long highest_memmap_pfn __read_mostly; +#ifdef CONFIG_UKSM +unsigned long uksm_zero_pfn __read_mostly; +EXPORT_SYMBOL_GPL(uksm_zero_pfn); +struct page *empty_uksm_zero_page; + +static int __init setup_uksm_zero_page(void) +{ + empty_uksm_zero_page = alloc_pages(__GFP_ZERO & ~__GFP_MOVABLE, 0); + if (!empty_uksm_zero_page) + panic("Oh boy, that early out of memory?"); + + SetPageReserved(empty_uksm_zero_page); + uksm_zero_pfn = page_to_pfn(empty_uksm_zero_page); + + return 0; +} +core_initcall(setup_uksm_zero_page); +#endif + /* * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init() */ @@ -139,6 +158,7 @@ static int __init init_zero_pfn(void) core_initcall(init_zero_pfn); + #if defined(SPLIT_RSS_COUNTING) void sync_mm_rss(struct mm_struct *mm) @@ -1039,6 +1059,9 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, get_page(page); page_dup_rmap(page, false); rss[mm_counter(page)]++; + + /* Should return NULL in vm_normal_page() */ + uksm_bugon_zeropage(pte); } else if (pte_devmap(pte)) { page = pte_page(pte); @@ -1052,6 +1075,8 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, page_dup_rmap(page, false); rss[mm_counter(page)]++; } + } else { + uksm_map_zero_page(pte); } out_set_pte: @@ -1321,8 +1346,10 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); tlb_remove_tlb_entry(tlb, pte, addr); - if (unlikely(!page)) + if (unlikely(!page)) { + uksm_unmap_zero_page(ptent); continue; + } if (!PageAnon(page)) { if (pte_dirty(ptent)) { @@ -2336,8 +2363,10 @@ static inline void cow_user_page(struct page *dst, struct page *src, unsigned lo clear_page(kaddr); kunmap_atomic(kaddr); flush_dcache_page(dst); - } else + } else { copy_user_highpage(dst, src, va, vma); + uksm_cow_page(vma, src); + } } static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma) @@ -2486,6 +2515,7 @@ static int wp_page_copy(struct vm_fault *vmf) vmf->address); if (!new_page) goto oom; + uksm_cow_pte(vma, vmf->orig_pte); } else { new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address); @@ -2512,7 +2542,9 @@ static int wp_page_copy(struct vm_fault *vmf) mm_counter_file(old_page)); inc_mm_counter_fast(mm, MM_ANONPAGES); } + uksm_bugon_zeropage(vmf->orig_pte); } else { + uksm_unmap_zero_page(vmf->orig_pte); inc_mm_counter_fast(mm, MM_ANONPAGES); } flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); diff --git a/mm/mmap.c b/mm/mmap.c index 9efdc021a..919ad70a7 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -45,6 +45,7 @@ #include #include #include +#include #include #include @@ -173,6 +174,7 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) if (vma->vm_file) fput(vma->vm_file); mpol_put(vma_policy(vma)); + uksm_remove_vma(vma); kmem_cache_free(vm_area_cachep, vma); return next; } @@ -692,9 +694,16 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, long adjust_next = 0; int remove_next = 0; +/* + * to avoid deadlock, ksm_remove_vma must be done before any spin_lock is + * acquired + */ + uksm_remove_vma(vma); + if (next && !insert) { struct vm_area_struct *exporter = NULL, *importer = NULL; + uksm_remove_vma(next); if (end >= next->vm_end) { /* * vma expands, overlapping all the next, and @@ -827,6 +836,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, end_changed = true; } vma->vm_pgoff = pgoff; + if (adjust_next) { next->vm_start += adjust_next << PAGE_SHIFT; next->vm_pgoff += adjust_next; @@ -932,6 +942,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, if (remove_next == 2) { remove_next = 1; end = next->vm_end; + uksm_remove_vma(next); goto again; } else if (next) @@ -958,10 +969,14 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, */ VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma)); } + } else { + if (next && !insert) + uksm_vma_add_new(next); } if (insert && file) uprobe_mmap(insert); + uksm_vma_add_new(vma); validate_mm(mm); return 0; @@ -1378,6 +1393,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr, vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) | mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; + /* If uksm is enabled, we add VM_MERGEABLE to new VMAs. */ + uksm_vm_flags_mod(&vm_flags); + if (flags & MAP_LOCKED) if (!can_do_mlock()) return -EPERM; @@ -1732,6 +1750,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, allow_write_access(file); } file = vma->vm_file; + uksm_vma_add_new(vma); out: perf_event_mmap(vma); @@ -1773,6 +1792,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, if (vm_flags & VM_DENYWRITE) allow_write_access(file); free_vma: + uksm_remove_vma(vma); kmem_cache_free(vm_area_cachep, vma); unacct_error: if (charged) @@ -2597,6 +2617,8 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, else err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new); + uksm_vma_add_new(new); + /* Success. */ if (!err) return 0; @@ -2889,6 +2911,7 @@ static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long if ((flags & (~VM_EXEC)) != 0) return -EINVAL; flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags; + uksm_vm_flags_mod(&flags); error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED); if (offset_in_page(error)) @@ -2946,6 +2969,7 @@ static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long vma->vm_flags = flags; vma->vm_page_prot = vm_get_page_prot(flags); vma_link(mm, vma, prev, rb_link, rb_parent); + uksm_vma_add_new(vma); out: perf_event_mmap(vma); mm->total_vm += len >> PAGE_SHIFT; @@ -2997,6 +3021,12 @@ void exit_mmap(struct mm_struct *mm) /* mm's last user has gone, and its about to be pulled down */ mmu_notifier_release(mm); + /* + * Taking write lock on mmap_sem does not harm others, + * but it's crucial for uksm to avoid races. + */ + down_write(&mm->mmap_sem); + if (mm->locked_vm) { vma = mm->mmap; while (vma) { @@ -3049,6 +3079,11 @@ void exit_mmap(struct mm_struct *mm) vma = remove_vma(vma); } vm_unacct_memory(nr_accounted); + + mm->mmap = NULL; + mm->mm_rb = RB_ROOT; + vmacache_invalidate(mm); + up_write(&mm->mmap_sem); } /* Insert vm structure into process list sorted by address @@ -3158,6 +3193,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, new_vma->vm_ops->open(new_vma); vma_link(mm, new_vma, prev, rb_link, rb_parent); *need_rmap_locks = false; + uksm_vma_add_new(new_vma); } return new_vma; @@ -3308,6 +3344,7 @@ static struct vm_area_struct *__install_special_mapping( vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT); perf_event_mmap(vma); + uksm_vma_add_new(vma); return vma; diff --git a/mm/rmap.c b/mm/rmap.c index 47db27f80..fdd0fd742 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1016,9 +1016,9 @@ void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma) /** * __page_set_anon_rmap - set up new anonymous rmap - * @page: Page to add to rmap + * @page: Page to add to rmap * @vma: VM area to add page to. - * @address: User virtual address of the mapping + * @address: User virtual address of the mapping * @exclusive: the page is exclusively owned by the current process */ static void __page_set_anon_rmap(struct page *page, diff --git a/mm/uksm.c b/mm/uksm.c new file mode 100644 index 000000000..48ddb7460 --- /dev/null +++ b/mm/uksm.c @@ -0,0 +1,5584 @@ +/* + * Ultra KSM. Copyright (C) 2011-2012 Nai Xia + * + * This is an improvement upon KSM. Some basic data structures and routines + * are borrowed from ksm.c . + * + * Its new features: + * 1. Full system scan: + * It automatically scans all user processes' anonymous VMAs. Kernel-user + * interaction to submit a memory area to KSM is no longer needed. + * + * 2. Rich area detection: + * It automatically detects rich areas containing abundant duplicated + * pages based. Rich areas are given a full scan speed. Poor areas are + * sampled at a reasonable speed with very low CPU consumption. + * + * 3. Ultra Per-page scan speed improvement: + * A new hash algorithm is proposed. As a result, on a machine with + * Core(TM)2 Quad Q9300 CPU in 32-bit mode and 800MHZ DDR2 main memory, it + * can scan memory areas that does not contain duplicated pages at speed of + * 627MB/sec ~ 2445MB/sec and can merge duplicated areas at speed of + * 477MB/sec ~ 923MB/sec. + * + * 4. Thrashing area avoidance: + * Thrashing area(an VMA that has frequent Ksm page break-out) can be + * filtered out. My benchmark shows it's more efficient than KSM's per-page + * hash value based volatile page detection. + * + * + * 5. Misc changes upon KSM: + * * It has a fully x86-opitmized memcmp dedicated for 4-byte-aligned page + * comparison. It's much faster than default C version on x86. + * * rmap_item now has an struct *page member to loosely cache a + * address-->page mapping, which reduces too much time-costly + * follow_page(). + * * The VMA creation/exit procedures are hooked to let the Ultra KSM know. + * * try_to_merge_two_pages() now can revert a pte if it fails. No break_ + * ksm is needed for this case. + * + * 6. Full Zero Page consideration(contributed by Figo Zhang) + * Now uksmd consider full zero pages as special pages and merge them to an + * special unswappable uksm zero page. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include "internal.h" + +#ifdef CONFIG_X86 +#undef memcmp + +#ifdef CONFIG_X86_32 +#define memcmp memcmpx86_32 +/* + * Compare 4-byte-aligned address s1 and s2, with length n + */ +int memcmpx86_32(void *s1, void *s2, size_t n) +{ + size_t num = n / 4; + register int res; + + __asm__ __volatile__ + ( + "testl %3,%3\n\t" + "repe; cmpsd\n\t" + "je 1f\n\t" + "sbbl %0,%0\n\t" + "orl $1,%0\n" + "1:" + : "=&a" (res), "+&S" (s1), "+&D" (s2), "+&c" (num) + : "0" (0) + : "cc"); + + return res; +} + +/* + * Check the page is all zero ? + */ +static int is_full_zero(const void *s1, size_t len) +{ + unsigned char same; + + len /= 4; + + __asm__ __volatile__ + ("repe; scasl;" + "sete %0" + : "=qm" (same), "+D" (s1), "+c" (len) + : "a" (0) + : "cc"); + + return same; +} + + +#elif defined(CONFIG_X86_64) +#define memcmp memcmpx86_64 +/* + * Compare 8-byte-aligned address s1 and s2, with length n + */ +int memcmpx86_64(void *s1, void *s2, size_t n) +{ + size_t num = n / 8; + register int res; + + __asm__ __volatile__ + ( + "testq %q3,%q3\n\t" + "repe; cmpsq\n\t" + "je 1f\n\t" + "sbbq %q0,%q0\n\t" + "orq $1,%q0\n" + "1:" + : "=&a" (res), "+&S" (s1), "+&D" (s2), "+&c" (num) + : "0" (0) + : "cc"); + + return res; +} + +static int is_full_zero(const void *s1, size_t len) +{ + unsigned char same; + + len /= 8; + + __asm__ __volatile__ + ("repe; scasq;" + "sete %0" + : "=qm" (same), "+D" (s1), "+c" (len) + : "a" (0) + : "cc"); + + return same; +} + +#endif +#else +static int is_full_zero(const void *s1, size_t len) +{ + unsigned long *src = s1; + int i; + + len /= sizeof(*src); + + for (i = 0; i < len; i++) { + if (src[i]) + return 0; + } + + return 1; +} +#endif + +#define UKSM_RUNG_ROUND_FINISHED (1 << 0) +#define TIME_RATIO_SCALE 10000 + +#define SLOT_TREE_NODE_SHIFT 8 +#define SLOT_TREE_NODE_STORE_SIZE (1UL << SLOT_TREE_NODE_SHIFT) +struct slot_tree_node { + unsigned long size; + struct sradix_tree_node snode; + void *stores[SLOT_TREE_NODE_STORE_SIZE]; +}; + +static struct kmem_cache *slot_tree_node_cachep; + +static struct sradix_tree_node *slot_tree_node_alloc(void) +{ + struct slot_tree_node *p; + + p = kmem_cache_zalloc(slot_tree_node_cachep, GFP_KERNEL | + __GFP_NORETRY | __GFP_NOWARN); + if (!p) + return NULL; + + return &p->snode; +} + +static void slot_tree_node_free(struct sradix_tree_node *node) +{ + struct slot_tree_node *p; + + p = container_of(node, struct slot_tree_node, snode); + kmem_cache_free(slot_tree_node_cachep, p); +} + +static void slot_tree_node_extend(struct sradix_tree_node *parent, + struct sradix_tree_node *child) +{ + struct slot_tree_node *p, *c; + + p = container_of(parent, struct slot_tree_node, snode); + c = container_of(child, struct slot_tree_node, snode); + + p->size += c->size; +} + +void slot_tree_node_assign(struct sradix_tree_node *node, + unsigned int index, void *item) +{ + struct vma_slot *slot = item; + struct slot_tree_node *cur; + + slot->snode = node; + slot->sindex = index; + + while (node) { + cur = container_of(node, struct slot_tree_node, snode); + cur->size += slot->pages; + node = node->parent; + } +} + +void slot_tree_node_rm(struct sradix_tree_node *node, unsigned int offset) +{ + struct vma_slot *slot; + struct slot_tree_node *cur; + unsigned long pages; + + if (node->height == 1) { + slot = node->stores[offset]; + pages = slot->pages; + } else { + cur = container_of(node->stores[offset], + struct slot_tree_node, snode); + pages = cur->size; + } + + while (node) { + cur = container_of(node, struct slot_tree_node, snode); + cur->size -= pages; + node = node->parent; + } +} + +unsigned long slot_iter_index; +int slot_iter(void *item, unsigned long height) +{ + struct slot_tree_node *node; + struct vma_slot *slot; + + if (height == 1) { + slot = item; + if (slot_iter_index < slot->pages) { + /*in this one*/ + return 1; + } else { + slot_iter_index -= slot->pages; + return 0; + } + + } else { + node = container_of(item, struct slot_tree_node, snode); + if (slot_iter_index < node->size) { + /*in this one*/ + return 1; + } else { + slot_iter_index -= node->size; + return 0; + } + } +} + + +static inline void slot_tree_init_root(struct sradix_tree_root *root) +{ + init_sradix_tree_root(root, SLOT_TREE_NODE_SHIFT); + root->alloc = slot_tree_node_alloc; + root->free = slot_tree_node_free; + root->extend = slot_tree_node_extend; + root->assign = slot_tree_node_assign; + root->rm = slot_tree_node_rm; +} + +void slot_tree_init(void) +{ + slot_tree_node_cachep = kmem_cache_create("slot_tree_node", + sizeof(struct slot_tree_node), 0, + SLAB_PANIC | SLAB_RECLAIM_ACCOUNT, + NULL); +} + + +/* Each rung of this ladder is a list of VMAs having a same scan ratio */ +struct scan_rung { + //struct list_head scanned_list; + struct sradix_tree_root vma_root; + struct sradix_tree_root vma_root2; + + struct vma_slot *current_scan; + unsigned long current_offset; + + /* + * The initial value for current_offset, it should loop over + * [0~ step - 1] to let all slot have its chance to be scanned. + */ + unsigned long offset_init; + unsigned long step; /* dynamic step for current_offset */ + unsigned int flags; + unsigned long pages_to_scan; + //unsigned long fully_scanned_slots; + /* + * a little bit tricky - if cpu_time_ratio > 0, then the value is the + * the cpu time ratio it can spend in rung_i for every scan + * period. if < 0, then it is the cpu time ratio relative to the + * max cpu percentage user specified. Both in unit of + * 1/TIME_RATIO_SCALE + */ + int cpu_ratio; + + /* + * How long it will take for all slots in this rung to be fully + * scanned? If it's zero, we don't care about the cover time: + * it's fully scanned. + */ + unsigned int cover_msecs; + //unsigned long vma_num; + //unsigned long pages; /* Sum of all slot's pages in rung */ +}; + +/** + * node of either the stable or unstale rbtree + * + */ +struct tree_node { + struct rb_node node; /* link in the main (un)stable rbtree */ + struct rb_root sub_root; /* rb_root for sublevel collision rbtree */ + u32 hash; + unsigned long count; /* TODO: merged with sub_root */ + struct list_head all_list; /* all tree nodes in stable/unstable tree */ +}; + +/** + * struct stable_node - node of the stable rbtree + * @node: rb node of this ksm page in the stable tree + * @hlist: hlist head of rmap_items using this ksm page + * @kpfn: page frame number of this ksm page + */ +struct stable_node { + struct rb_node node; /* link in sub-rbtree */ + struct tree_node *tree_node; /* it's tree node root in stable tree, NULL if it's in hell list */ + struct hlist_head hlist; + unsigned long kpfn; + u32 hash_max; /* if ==0 then it's not been calculated yet */ + struct list_head all_list; /* in a list for all stable nodes */ +}; + +/** + * struct node_vma - group rmap_items linked in a same stable + * node together. + */ +struct node_vma { + union { + struct vma_slot *slot; + unsigned long key; /* slot is used as key sorted on hlist */ + }; + struct hlist_node hlist; + struct hlist_head rmap_hlist; + struct stable_node *head; +}; + +/** + * struct rmap_item - reverse mapping item for virtual addresses + * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list + * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree + * @mm: the memory structure this rmap_item is pointing into + * @address: the virtual address this rmap_item tracks (+ flags in low bits) + * @node: rb node of this rmap_item in the unstable tree + * @head: pointer to stable_node heading this list in the stable tree + * @hlist: link into hlist of rmap_items hanging off that stable_node + */ +struct rmap_item { + struct vma_slot *slot; + struct page *page; + unsigned long address; /* + low bits used for flags below */ + unsigned long hash_round; + unsigned long entry_index; + union { + struct {/* when in unstable tree */ + struct rb_node node; + struct tree_node *tree_node; + u32 hash_max; + }; + struct { /* when in stable tree */ + struct node_vma *head; + struct hlist_node hlist; + struct anon_vma *anon_vma; + }; + }; +} __aligned(4); + +struct rmap_list_entry { + union { + struct rmap_item *item; + unsigned long addr; + }; + /* lowest bit is used for is_addr tag */ +} __aligned(4); /* 4 aligned to fit in to pages*/ + + +/* Basic data structure definition ends */ + + +/* + * Flags for rmap_item to judge if it's listed in the stable/unstable tree. + * The flags use the low bits of rmap_item.address + */ +#define UNSTABLE_FLAG 0x1 +#define STABLE_FLAG 0x2 +#define get_rmap_addr(x) ((x)->address & PAGE_MASK) + +/* + * rmap_list_entry helpers + */ +#define IS_ADDR_FLAG 1 +#define is_addr(ptr) ((unsigned long)(ptr) & IS_ADDR_FLAG) +#define set_is_addr(ptr) ((ptr) |= IS_ADDR_FLAG) +#define get_clean_addr(ptr) (((ptr) & ~(__typeof__(ptr))IS_ADDR_FLAG)) + + +/* + * High speed caches for frequently allocated and freed structs + */ +static struct kmem_cache *rmap_item_cache; +static struct kmem_cache *stable_node_cache; +static struct kmem_cache *node_vma_cache; +static struct kmem_cache *vma_slot_cache; +static struct kmem_cache *tree_node_cache; +#define UKSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("uksm_"#__struct,\ + sizeof(struct __struct), __alignof__(struct __struct),\ + (__flags), NULL) + +/* Array of all scan_rung, uksm_scan_ladder[0] having the minimum scan ratio */ +#define SCAN_LADDER_SIZE 4 +static struct scan_rung uksm_scan_ladder[SCAN_LADDER_SIZE]; + +/* The evaluation rounds uksmd has finished */ +static unsigned long long uksm_eval_round = 1; + +/* + * we add 1 to this var when we consider we should rebuild the whole + * unstable tree. + */ +static unsigned long uksm_hash_round = 1; + +/* + * How many times the whole memory is scanned. + */ +static unsigned long long fully_scanned_round = 1; + +/* The total number of virtual pages of all vma slots */ +static u64 uksm_pages_total; + +/* The number of pages has been scanned since the start up */ +static u64 uksm_pages_scanned; + +static u64 scanned_virtual_pages; + +/* The number of pages has been scanned since last encode_benefit call */ +static u64 uksm_pages_scanned_last; + +/* If the scanned number is tooo large, we encode it here */ +static u64 pages_scanned_stored; + +static unsigned long pages_scanned_base; + +/* The number of nodes in the stable tree */ +static unsigned long uksm_pages_shared; + +/* The number of page slots additionally sharing those nodes */ +static unsigned long uksm_pages_sharing; + +/* The number of nodes in the unstable tree */ +static unsigned long uksm_pages_unshared; + +/* + * Milliseconds ksmd should sleep between scans, + * >= 100ms to be consistent with + * scan_time_to_sleep_msec() + */ +static unsigned int uksm_sleep_jiffies; + +/* The real value for the uksmd next sleep */ +static unsigned int uksm_sleep_real; + +/* Saved value for user input uksm_sleep_jiffies when it's enlarged */ +static unsigned int uksm_sleep_saved; + +/* Max percentage of cpu utilization ksmd can take to scan in one batch */ +static unsigned int uksm_max_cpu_percentage; + +static int uksm_cpu_governor; + +static char *uksm_cpu_governor_str[4] = { "full", "medium", "low", "quiet" }; + +struct uksm_cpu_preset_s { + int cpu_ratio[SCAN_LADDER_SIZE]; + unsigned int cover_msecs[SCAN_LADDER_SIZE]; + unsigned int max_cpu; /* percentage */ +}; + +struct uksm_cpu_preset_s uksm_cpu_preset[4] = { + { {20, 40, -2500, -10000}, {1000, 500, 200, 50}, 95}, + { {20, 30, -2500, -10000}, {1000, 500, 400, 100}, 50}, + { {10, 20, -5000, -10000}, {1500, 1000, 1000, 250}, 20}, + { {10, 20, 40, 75}, {2000, 1000, 1000, 1000}, 1}, +}; + +/* The default value for uksm_ema_page_time if it's not initialized */ +#define UKSM_PAGE_TIME_DEFAULT 500 + +/*cost to scan one page by expotional moving average in nsecs */ +static unsigned long uksm_ema_page_time = UKSM_PAGE_TIME_DEFAULT; + +/* The expotional moving average alpha weight, in percentage. */ +#define EMA_ALPHA 20 + +/* + * The threshold used to filter out thrashing areas, + * If it == 0, filtering is disabled, otherwise it's the percentage up-bound + * of the thrashing ratio of all areas. Any area with a bigger thrashing ratio + * will be considered as having a zero duplication ratio. + */ +static unsigned int uksm_thrash_threshold = 50; + +/* How much dedup ratio is considered to be abundant*/ +static unsigned int uksm_abundant_threshold = 10; + +/* All slots having merged pages in this eval round. */ +struct list_head vma_slot_dedup = LIST_HEAD_INIT(vma_slot_dedup); + +/* How many times the ksmd has slept since startup */ +static unsigned long long uksm_sleep_times; + +#define UKSM_RUN_STOP 0 +#define UKSM_RUN_MERGE 1 +static unsigned int uksm_run = 1; + +static DECLARE_WAIT_QUEUE_HEAD(uksm_thread_wait); +static DEFINE_MUTEX(uksm_thread_mutex); + +/* + * List vma_slot_new is for newly created vma_slot waiting to be added by + * ksmd. If one cannot be added(e.g. due to it's too small), it's moved to + * vma_slot_noadd. vma_slot_del is the list for vma_slot whose corresponding + * VMA has been removed/freed. + */ +struct list_head vma_slot_new = LIST_HEAD_INIT(vma_slot_new); +struct list_head vma_slot_noadd = LIST_HEAD_INIT(vma_slot_noadd); +struct list_head vma_slot_del = LIST_HEAD_INIT(vma_slot_del); +static DEFINE_SPINLOCK(vma_slot_list_lock); + +/* The unstable tree heads */ +static struct rb_root root_unstable_tree = RB_ROOT; + +/* + * All tree_nodes are in a list to be freed at once when unstable tree is + * freed after each scan round. + */ +static struct list_head unstable_tree_node_list = + LIST_HEAD_INIT(unstable_tree_node_list); + +/* List contains all stable nodes */ +static struct list_head stable_node_list = LIST_HEAD_INIT(stable_node_list); + +/* + * When the hash strength is changed, the stable tree must be delta_hashed and + * re-structured. We use two set of below structs to speed up the + * re-structuring of stable tree. + */ +static struct list_head +stable_tree_node_list[2] = {LIST_HEAD_INIT(stable_tree_node_list[0]), + LIST_HEAD_INIT(stable_tree_node_list[1])}; + +static struct list_head *stable_tree_node_listp = &stable_tree_node_list[0]; +static struct rb_root root_stable_tree[2] = {RB_ROOT, RB_ROOT}; +static struct rb_root *root_stable_treep = &root_stable_tree[0]; +static unsigned long stable_tree_index; + +/* The hash strength needed to hash a full page */ +#define HASH_STRENGTH_FULL (PAGE_SIZE / sizeof(u32)) + +/* The hash strength needed for loop-back hashing */ +#define HASH_STRENGTH_MAX (HASH_STRENGTH_FULL + 10) + +/* The random offsets in a page */ +static u32 *random_nums; + +/* The hash strength */ +static unsigned long hash_strength = HASH_STRENGTH_FULL >> 4; + +/* The delta value each time the hash strength increases or decreases */ +static unsigned long hash_strength_delta; +#define HASH_STRENGTH_DELTA_MAX 5 + +/* The time we have saved due to random_sample_hash */ +static u64 rshash_pos; + +/* The time we have wasted due to hash collision */ +static u64 rshash_neg; + +struct uksm_benefit { + u64 pos; + u64 neg; + u64 scanned; + unsigned long base; +} benefit; + +/* + * The relative cost of memcmp, compared to 1 time unit of random sample + * hash, this value is tested when ksm module is initialized + */ +static unsigned long memcmp_cost; + +static unsigned long rshash_neg_cont_zero; +static unsigned long rshash_cont_obscure; + +/* The possible states of hash strength adjustment heuristic */ +enum rshash_states { + RSHASH_STILL, + RSHASH_TRYUP, + RSHASH_TRYDOWN, + RSHASH_NEW, + RSHASH_PRE_STILL, +}; + +/* The possible direction we are about to adjust hash strength */ +enum rshash_direct { + GO_UP, + GO_DOWN, + OBSCURE, + STILL, +}; + +/* random sampling hash state machine */ +static struct { + enum rshash_states state; + enum rshash_direct pre_direct; + u8 below_count; + /* Keep a lookup window of size 5, iff above_count/below_count > 3 + * in this window we stop trying. + */ + u8 lookup_window_index; + u64 stable_benefit; + unsigned long turn_point_down; + unsigned long turn_benefit_down; + unsigned long turn_point_up; + unsigned long turn_benefit_up; + unsigned long stable_point; +} rshash_state; + +/*zero page hash table, hash_strength [0 ~ HASH_STRENGTH_MAX]*/ +static u32 *zero_hash_table; + +static inline struct node_vma *alloc_node_vma(void) +{ + struct node_vma *node_vma; + + node_vma = kmem_cache_zalloc(node_vma_cache, GFP_KERNEL | + __GFP_NORETRY | __GFP_NOWARN); + if (node_vma) { + INIT_HLIST_HEAD(&node_vma->rmap_hlist); + INIT_HLIST_NODE(&node_vma->hlist); + } + return node_vma; +} + +static inline void free_node_vma(struct node_vma *node_vma) +{ + kmem_cache_free(node_vma_cache, node_vma); +} + + +static inline struct vma_slot *alloc_vma_slot(void) +{ + struct vma_slot *slot; + + /* + * In case ksm is not initialized by now. + * Oops, we need to consider the call site of uksm_init() in the future. + */ + if (!vma_slot_cache) + return NULL; + + slot = kmem_cache_zalloc(vma_slot_cache, GFP_KERNEL | + __GFP_NORETRY | __GFP_NOWARN); + if (slot) { + INIT_LIST_HEAD(&slot->slot_list); + INIT_LIST_HEAD(&slot->dedup_list); + slot->flags |= UKSM_SLOT_NEED_RERAND; + } + return slot; +} + +static inline void free_vma_slot(struct vma_slot *vma_slot) +{ + kmem_cache_free(vma_slot_cache, vma_slot); +} + + + +static inline struct rmap_item *alloc_rmap_item(void) +{ + struct rmap_item *rmap_item; + + rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL | + __GFP_NORETRY | __GFP_NOWARN); + if (rmap_item) { + /* bug on lowest bit is not clear for flag use */ + BUG_ON(is_addr(rmap_item)); + } + return rmap_item; +} + +static inline void free_rmap_item(struct rmap_item *rmap_item) +{ + rmap_item->slot = NULL; /* debug safety */ + kmem_cache_free(rmap_item_cache, rmap_item); +} + +static inline struct stable_node *alloc_stable_node(void) +{ + struct stable_node *node; + + node = kmem_cache_alloc(stable_node_cache, GFP_KERNEL | + __GFP_NORETRY | __GFP_NOWARN); + if (!node) + return NULL; + + INIT_HLIST_HEAD(&node->hlist); + list_add(&node->all_list, &stable_node_list); + return node; +} + +static inline void free_stable_node(struct stable_node *stable_node) +{ + list_del(&stable_node->all_list); + kmem_cache_free(stable_node_cache, stable_node); +} + +static inline struct tree_node *alloc_tree_node(struct list_head *list) +{ + struct tree_node *node; + + node = kmem_cache_zalloc(tree_node_cache, GFP_KERNEL | + __GFP_NORETRY | __GFP_NOWARN); + if (!node) + return NULL; + + list_add(&node->all_list, list); + return node; +} + +static inline void free_tree_node(struct tree_node *node) +{ + list_del(&node->all_list); + kmem_cache_free(tree_node_cache, node); +} + +static void uksm_drop_anon_vma(struct rmap_item *rmap_item) +{ + struct anon_vma *anon_vma = rmap_item->anon_vma; + + put_anon_vma(anon_vma); +} + + +/** + * Remove a stable node from stable_tree, may unlink from its tree_node and + * may remove its parent tree_node if no other stable node is pending. + * + * @stable_node The node need to be removed + * @unlink_rb Will this node be unlinked from the rbtree? + * @remove_tree_ node Will its tree_node be removed if empty? + */ +static void remove_node_from_stable_tree(struct stable_node *stable_node, + int unlink_rb, int remove_tree_node) +{ + struct node_vma *node_vma; + struct rmap_item *rmap_item; + struct hlist_node *n; + + if (!hlist_empty(&stable_node->hlist)) { + hlist_for_each_entry_safe(node_vma, n, + &stable_node->hlist, hlist) { + hlist_for_each_entry(rmap_item, &node_vma->rmap_hlist, hlist) { + uksm_pages_sharing--; + + uksm_drop_anon_vma(rmap_item); + rmap_item->address &= PAGE_MASK; + } + free_node_vma(node_vma); + cond_resched(); + } + + /* the last one is counted as shared */ + uksm_pages_shared--; + uksm_pages_sharing++; + } + + if (stable_node->tree_node && unlink_rb) { + rb_erase(&stable_node->node, + &stable_node->tree_node->sub_root); + + if (RB_EMPTY_ROOT(&stable_node->tree_node->sub_root) && + remove_tree_node) { + rb_erase(&stable_node->tree_node->node, + root_stable_treep); + free_tree_node(stable_node->tree_node); + } else { + stable_node->tree_node->count--; + } + } + + free_stable_node(stable_node); +} + + +/* + * get_uksm_page: checks if the page indicated by the stable node + * is still its ksm page, despite having held no reference to it. + * In which case we can trust the content of the page, and it + * returns the gotten page; but if the page has now been zapped, + * remove the stale node from the stable tree and return NULL. + * + * You would expect the stable_node to hold a reference to the ksm page. + * But if it increments the page's count, swapping out has to wait for + * ksmd to come around again before it can free the page, which may take + * seconds or even minutes: much too unresponsive. So instead we use a + * "keyhole reference": access to the ksm page from the stable node peeps + * out through its keyhole to see if that page still holds the right key, + * pointing back to this stable node. This relies on freeing a PageAnon + * page to reset its page->mapping to NULL, and relies on no other use of + * a page to put something that might look like our key in page->mapping. + * + * include/linux/pagemap.h page_cache_get_speculative() is a good reference, + * but this is different - made simpler by uksm_thread_mutex being held, but + * interesting for assuming that no other use of the struct page could ever + * put our expected_mapping into page->mapping (or a field of the union which + * coincides with page->mapping). The RCU calls are not for KSM at all, but + * to keep the page_count protocol described with page_cache_get_speculative. + * + * Note: it is possible that get_uksm_page() will return NULL one moment, + * then page the next, if the page is in between page_freeze_refs() and + * page_unfreeze_refs(): this shouldn't be a problem anywhere, the page + * is on its way to being freed; but it is an anomaly to bear in mind. + * + * @unlink_rb: if the removal of this node will firstly unlink from + * its rbtree. stable_node_reinsert will prevent this when restructuring the + * node from its old tree. + * + * @remove_tree_node: if this is the last one of its tree_node, will the + * tree_node be freed ? If we are inserting stable node, this tree_node may + * be reused, so don't free it. + */ +static struct page *get_uksm_page(struct stable_node *stable_node, + int unlink_rb, int remove_tree_node) +{ + struct page *page; + void *expected_mapping; + unsigned long kpfn; + + expected_mapping = (void *)((unsigned long)stable_node | + PAGE_MAPPING_KSM); +again: + kpfn = READ_ONCE(stable_node->kpfn); + page = pfn_to_page(kpfn); + + /* + * page is computed from kpfn, so on most architectures reading + * page->mapping is naturally ordered after reading node->kpfn, + * but on Alpha we need to be more careful. + */ + smp_read_barrier_depends(); + + if (READ_ONCE(page->mapping) != expected_mapping) + goto stale; + + /* + * We cannot do anything with the page while its refcount is 0. + * Usually 0 means free, or tail of a higher-order page: in which + * case this node is no longer referenced, and should be freed; + * however, it might mean that the page is under page_freeze_refs(). + * The __remove_mapping() case is easy, again the node is now stale; + * but if page is swapcache in migrate_page_move_mapping(), it might + * still be our page, in which case it's essential to keep the node. + */ + while (!get_page_unless_zero(page)) { + /* + * Another check for page->mapping != expected_mapping would + * work here too. We have chosen the !PageSwapCache test to + * optimize the common case, when the page is or is about to + * be freed: PageSwapCache is cleared (under spin_lock_irq) + * in the freeze_refs section of __remove_mapping(); but Anon + * page->mapping reset to NULL later, in free_pages_prepare(). + */ + if (!PageSwapCache(page)) + goto stale; + cpu_relax(); + } + + if (READ_ONCE(page->mapping) != expected_mapping) { + put_page(page); + goto stale; + } + + lock_page(page); + if (READ_ONCE(page->mapping) != expected_mapping) { + unlock_page(page); + put_page(page); + goto stale; + } + unlock_page(page); + return page; +stale: + /* + * We come here from above when page->mapping or !PageSwapCache + * suggests that the node is stale; but it might be under migration. + * We need smp_rmb(), matching the smp_wmb() in ksm_migrate_page(), + * before checking whether node->kpfn has been changed. + */ + smp_rmb(); + if (stable_node->kpfn != kpfn) + goto again; + + remove_node_from_stable_tree(stable_node, unlink_rb, remove_tree_node); + + return NULL; +} + +/* + * Removing rmap_item from stable or unstable tree. + * This function will clean the information from the stable/unstable tree. + */ +static inline void remove_rmap_item_from_tree(struct rmap_item *rmap_item) +{ + if (rmap_item->address & STABLE_FLAG) { + struct stable_node *stable_node; + struct node_vma *node_vma; + struct page *page; + + node_vma = rmap_item->head; + stable_node = node_vma->head; + page = get_uksm_page(stable_node, 1, 1); + if (!page) + goto out; + + /* + * page lock is needed because it's racing with + * try_to_unmap_ksm(), etc. + */ + lock_page(page); + hlist_del(&rmap_item->hlist); + + if (hlist_empty(&node_vma->rmap_hlist)) { + hlist_del(&node_vma->hlist); + free_node_vma(node_vma); + } + unlock_page(page); + + put_page(page); + if (hlist_empty(&stable_node->hlist)) { + /* do NOT call remove_node_from_stable_tree() here, + * it's possible for a forked rmap_item not in + * stable tree while the in-tree rmap_items were + * deleted. + */ + uksm_pages_shared--; + } else + uksm_pages_sharing--; + + + uksm_drop_anon_vma(rmap_item); + } else if (rmap_item->address & UNSTABLE_FLAG) { + if (rmap_item->hash_round == uksm_hash_round) { + + rb_erase(&rmap_item->node, + &rmap_item->tree_node->sub_root); + if (RB_EMPTY_ROOT(&rmap_item->tree_node->sub_root)) { + rb_erase(&rmap_item->tree_node->node, + &root_unstable_tree); + + free_tree_node(rmap_item->tree_node); + } else + rmap_item->tree_node->count--; + } + uksm_pages_unshared--; + } + + rmap_item->address &= PAGE_MASK; + rmap_item->hash_max = 0; + +out: + cond_resched(); /* we're called from many long loops */ +} + +static inline int slot_in_uksm(struct vma_slot *slot) +{ + return list_empty(&slot->slot_list); +} + +/* + * Test if the mm is exiting + */ +static inline bool uksm_test_exit(struct mm_struct *mm) +{ + return atomic_read(&mm->mm_users) == 0; +} + +static inline unsigned long vma_pool_size(struct vma_slot *slot) +{ + return round_up(sizeof(struct rmap_list_entry) * slot->pages, + PAGE_SIZE) >> PAGE_SHIFT; +} + +#define CAN_OVERFLOW_U64(x, delta) (U64_MAX - (x) < (delta)) + +/* must be done with sem locked */ +static int slot_pool_alloc(struct vma_slot *slot) +{ + unsigned long pool_size; + + if (slot->rmap_list_pool) + return 0; + + pool_size = vma_pool_size(slot); + slot->rmap_list_pool = kcalloc(pool_size, sizeof(struct page *), + GFP_KERNEL); + if (!slot->rmap_list_pool) + return -ENOMEM; + + slot->pool_counts = kcalloc(pool_size, sizeof(unsigned int), + GFP_KERNEL); + if (!slot->pool_counts) { + kfree(slot->rmap_list_pool); + return -ENOMEM; + } + + slot->pool_size = pool_size; + BUG_ON(CAN_OVERFLOW_U64(uksm_pages_total, slot->pages)); + slot->flags |= UKSM_SLOT_IN_UKSM; + uksm_pages_total += slot->pages; + + return 0; +} + +/* + * Called after vma is unlinked from its mm + */ +void uksm_remove_vma(struct vm_area_struct *vma) +{ + struct vma_slot *slot; + + if (!vma->uksm_vma_slot) + return; + + spin_lock(&vma_slot_list_lock); + slot = vma->uksm_vma_slot; + if (!slot) + goto out; + + if (slot_in_uksm(slot)) { + /** + * This slot has been added by ksmd, so move to the del list + * waiting ksmd to free it. + */ + list_add_tail(&slot->slot_list, &vma_slot_del); + } else { + /** + * It's still on new list. It's ok to free slot directly. + */ + list_del(&slot->slot_list); + free_vma_slot(slot); + } +out: + vma->uksm_vma_slot = NULL; + spin_unlock(&vma_slot_list_lock); +} + +/** + * Need to do two things: + * 1. check if slot was moved to del list + * 2. make sure the mmap_sem is manipulated under valid vma. + * + * My concern here is that in some cases, this may make + * vma_slot_list_lock() waiters to serialized further by some + * sem->wait_lock, can this really be expensive? + * + * + * @return + * 0: if successfully locked mmap_sem + * -ENOENT: this slot was moved to del list + * -EBUSY: vma lock failed + */ +static int try_down_read_slot_mmap_sem(struct vma_slot *slot) +{ + struct vm_area_struct *vma; + struct mm_struct *mm; + struct rw_semaphore *sem; + + spin_lock(&vma_slot_list_lock); + + /* the slot_list was removed and inited from new list, when it enters + * uksm_list. If now it's not empty, then it must be moved to del list + */ + if (!slot_in_uksm(slot)) { + spin_unlock(&vma_slot_list_lock); + return -ENOENT; + } + + BUG_ON(slot->pages != vma_pages(slot->vma)); + /* Ok, vma still valid */ + vma = slot->vma; + mm = vma->vm_mm; + sem = &mm->mmap_sem; + + if (uksm_test_exit(mm)) { + spin_unlock(&vma_slot_list_lock); + return -ENOENT; + } + + if (down_read_trylock(sem)) { + spin_unlock(&vma_slot_list_lock); + if (slot_pool_alloc(slot)) { + uksm_remove_vma(vma); + up_read(sem); + return -ENOENT; + } + return 0; + } + + spin_unlock(&vma_slot_list_lock); + return -EBUSY; +} + +static inline unsigned long +vma_page_address(struct page *page, struct vm_area_struct *vma) +{ + pgoff_t pgoff = page->index; + unsigned long address; + + address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); + if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { + /* page should be within @vma mapping range */ + return -EFAULT; + } + return address; +} + + +/* return 0 on success with the item's mmap_sem locked */ +static inline int get_mergeable_page_lock_mmap(struct rmap_item *item) +{ + struct mm_struct *mm; + struct vma_slot *slot = item->slot; + int err = -EINVAL; + + struct page *page; + + /* + * try_down_read_slot_mmap_sem() returns non-zero if the slot + * has been removed by uksm_remove_vma(). + */ + if (try_down_read_slot_mmap_sem(slot)) + return -EBUSY; + + mm = slot->vma->vm_mm; + + if (uksm_test_exit(mm)) + goto failout_up; + + page = item->page; + rcu_read_lock(); + if (!get_page_unless_zero(page)) { + rcu_read_unlock(); + goto failout_up; + } + + /* No need to consider huge page here. */ + if (item->slot->vma->anon_vma != page_anon_vma(page) || + vma_page_address(page, item->slot->vma) != get_rmap_addr(item)) { + /* + * TODO: + * should we release this item becase of its stale page + * mapping? + */ + put_page(page); + rcu_read_unlock(); + goto failout_up; + } + rcu_read_unlock(); + return 0; + +failout_up: + up_read(&mm->mmap_sem); + return err; +} + +/* + * What kind of VMA is considered ? + */ +static inline int vma_can_enter(struct vm_area_struct *vma) +{ + return uksm_flags_can_scan(vma->vm_flags); +} + +/* + * Called whenever a fresh new vma is created A new vma_slot. + * is created and inserted into a global list Must be called. + * after vma is inserted to its mm. + */ +void uksm_vma_add_new(struct vm_area_struct *vma) +{ + struct vma_slot *slot; + + if (!vma_can_enter(vma)) { + vma->uksm_vma_slot = NULL; + return; + } + + slot = alloc_vma_slot(); + if (!slot) { + vma->uksm_vma_slot = NULL; + return; + } + + vma->uksm_vma_slot = slot; + vma->vm_flags |= VM_MERGEABLE; + slot->vma = vma; + slot->mm = vma->vm_mm; + slot->ctime_j = jiffies; + slot->pages = vma_pages(vma); + spin_lock(&vma_slot_list_lock); + list_add_tail(&slot->slot_list, &vma_slot_new); + spin_unlock(&vma_slot_list_lock); +} + +/* 32/3 < they < 32/2 */ +#define shiftl 8 +#define shiftr 12 + +#define HASH_FROM_TO(from, to) \ +for (index = from; index < to; index++) { \ + pos = random_nums[index]; \ + hash += key[pos]; \ + hash += (hash << shiftl); \ + hash ^= (hash >> shiftr); \ +} + + +#define HASH_FROM_DOWN_TO(from, to) \ +for (index = from - 1; index >= to; index--) { \ + hash ^= (hash >> shiftr); \ + hash ^= (hash >> (shiftr*2)); \ + hash -= (hash << shiftl); \ + hash += (hash << (shiftl*2)); \ + pos = random_nums[index]; \ + hash -= key[pos]; \ +} + +/* + * The main random sample hash function. + */ +static u32 random_sample_hash(void *addr, u32 hash_strength) +{ + u32 hash = 0xdeadbeef; + int index, pos, loop = hash_strength; + u32 *key = (u32 *)addr; + + if (loop > HASH_STRENGTH_FULL) + loop = HASH_STRENGTH_FULL; + + HASH_FROM_TO(0, loop); + + if (hash_strength > HASH_STRENGTH_FULL) { + loop = hash_strength - HASH_STRENGTH_FULL; + HASH_FROM_TO(0, loop); + } + + return hash; +} + + +/** + * It's used when hash strength is adjusted + * + * @addr The page's virtual address + * @from The original hash strength + * @to The hash strength changed to + * @hash The hash value generated with "from" hash value + * + * return the hash value + */ +static u32 delta_hash(void *addr, int from, int to, u32 hash) +{ + u32 *key = (u32 *)addr; + int index, pos; /* make sure they are int type */ + + if (to > from) { + if (from >= HASH_STRENGTH_FULL) { + from -= HASH_STRENGTH_FULL; + to -= HASH_STRENGTH_FULL; + HASH_FROM_TO(from, to); + } else if (to <= HASH_STRENGTH_FULL) { + HASH_FROM_TO(from, to); + } else { + HASH_FROM_TO(from, HASH_STRENGTH_FULL); + HASH_FROM_TO(0, to - HASH_STRENGTH_FULL); + } + } else { + if (from <= HASH_STRENGTH_FULL) { + HASH_FROM_DOWN_TO(from, to); + } else if (to >= HASH_STRENGTH_FULL) { + from -= HASH_STRENGTH_FULL; + to -= HASH_STRENGTH_FULL; + HASH_FROM_DOWN_TO(from, to); + } else { + HASH_FROM_DOWN_TO(from - HASH_STRENGTH_FULL, 0); + HASH_FROM_DOWN_TO(HASH_STRENGTH_FULL, to); + } + } + + return hash; +} + +/** + * + * Called when: rshash_pos or rshash_neg is about to overflow or a scan round + * has finished. + * + * return 0 if no page has been scanned since last call, 1 otherwise. + */ +static inline int encode_benefit(void) +{ + u64 scanned_delta, pos_delta, neg_delta; + unsigned long base = benefit.base; + + scanned_delta = uksm_pages_scanned - uksm_pages_scanned_last; + + if (!scanned_delta) + return 0; + + scanned_delta >>= base; + pos_delta = rshash_pos >> base; + neg_delta = rshash_neg >> base; + + if (CAN_OVERFLOW_U64(benefit.pos, pos_delta) || + CAN_OVERFLOW_U64(benefit.neg, neg_delta) || + CAN_OVERFLOW_U64(benefit.scanned, scanned_delta)) { + benefit.scanned >>= 1; + benefit.neg >>= 1; + benefit.pos >>= 1; + benefit.base++; + scanned_delta >>= 1; + pos_delta >>= 1; + neg_delta >>= 1; + } + + benefit.pos += pos_delta; + benefit.neg += neg_delta; + benefit.scanned += scanned_delta; + + BUG_ON(!benefit.scanned); + + rshash_pos = rshash_neg = 0; + uksm_pages_scanned_last = uksm_pages_scanned; + + return 1; +} + +static inline void reset_benefit(void) +{ + benefit.pos = 0; + benefit.neg = 0; + benefit.base = 0; + benefit.scanned = 0; +} + +static inline void inc_rshash_pos(unsigned long delta) +{ + if (CAN_OVERFLOW_U64(rshash_pos, delta)) + encode_benefit(); + + rshash_pos += delta; +} + +static inline void inc_rshash_neg(unsigned long delta) +{ + if (CAN_OVERFLOW_U64(rshash_neg, delta)) + encode_benefit(); + + rshash_neg += delta; +} + + +static inline u32 page_hash(struct page *page, unsigned long hash_strength, + int cost_accounting) +{ + u32 val; + unsigned long delta; + + void *addr = kmap_atomic(page); + + val = random_sample_hash(addr, hash_strength); + kunmap_atomic(addr); + + if (cost_accounting) { + if (hash_strength < HASH_STRENGTH_FULL) + delta = HASH_STRENGTH_FULL - hash_strength; + else + delta = 0; + + inc_rshash_pos(delta); + } + + return val; +} + +static int memcmp_pages(struct page *page1, struct page *page2, + int cost_accounting) +{ + char *addr1, *addr2; + int ret; + + addr1 = kmap_atomic(page1); + addr2 = kmap_atomic(page2); + ret = memcmp(addr1, addr2, PAGE_SIZE); + kunmap_atomic(addr2); + kunmap_atomic(addr1); + + if (cost_accounting) + inc_rshash_neg(memcmp_cost); + + return ret; +} + +static inline int pages_identical(struct page *page1, struct page *page2) +{ + return !memcmp_pages(page1, page2, 0); +} + +static inline int is_page_full_zero(struct page *page) +{ + char *addr; + int ret; + + addr = kmap_atomic(page); + ret = is_full_zero(addr, PAGE_SIZE); + kunmap_atomic(addr); + + return ret; +} + +static int write_protect_page(struct vm_area_struct *vma, struct page *page, + pte_t *orig_pte, pte_t *old_pte) +{ + struct mm_struct *mm = vma->vm_mm; + struct page_vma_mapped_walk pvmw = { + .page = page, + .vma = vma, + }; + int swapped; + int err = -EFAULT; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ + + pvmw.address = page_address_in_vma(page, vma); + if (pvmw.address == -EFAULT) + goto out; + + BUG_ON(PageTransCompound(page)); + + mmun_start = pvmw.address; + mmun_end = pvmw.address + PAGE_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + + if (!page_vma_mapped_walk(&pvmw)) + goto out_mn; + if (WARN_ONCE(!pvmw.pte, "Unexpected PMD mapping?")) + goto out_unlock; + + if (old_pte) + *old_pte = *pvmw.pte; + + if (pte_write(*pvmw.pte) || pte_dirty(*pvmw.pte) || + (pte_protnone(*pvmw.pte) && pte_savedwrite(*pvmw.pte)) || mm_tlb_flush_pending(mm)) { + pte_t entry; + + swapped = PageSwapCache(page); + flush_cache_page(vma, pvmw.address, page_to_pfn(page)); + /* + * Ok this is tricky, when get_user_pages_fast() run it doesn't + * take any lock, therefore the check that we are going to make + * with the pagecount against the mapcount is racey and + * O_DIRECT can happen right after the check. + * So we clear the pte and flush the tlb before the check + * this assure us that no O_DIRECT can happen after the check + * or in the middle of the check. + */ + entry = ptep_clear_flush_notify(vma, pvmw.address, pvmw.pte); + /* + * Check that no O_DIRECT or similar I/O is in progress on the + * page + */ + if (page_mapcount(page) + 1 + swapped != page_count(page)) { + set_pte_at(mm, pvmw.address, pvmw.pte, entry); + goto out_unlock; + } + if (pte_dirty(entry)) + set_page_dirty(page); + + if (pte_protnone(entry)) + entry = pte_mkclean(pte_clear_savedwrite(entry)); + else + entry = pte_mkclean(pte_wrprotect(entry)); + + set_pte_at_notify(mm, pvmw.address, pvmw.pte, entry); + } + *orig_pte = *pvmw.pte; + err = 0; + +out_unlock: + page_vma_mapped_walk_done(&pvmw); +out_mn: + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); +out: + return err; +} + +#define MERGE_ERR_PGERR 1 /* the page is invalid cannot continue */ +#define MERGE_ERR_COLLI 2 /* there is a collision */ +#define MERGE_ERR_COLLI_MAX 3 /* collision at the max hash strength */ +#define MERGE_ERR_CHANGED 4 /* the page has changed since last hash */ + + +/** + * replace_page - replace page in vma by new ksm page + * @vma: vma that holds the pte pointing to page + * @page: the page we are replacing by kpage + * @kpage: the ksm page we replace page by + * @orig_pte: the original value of the pte + * + * Returns 0 on success, MERGE_ERR_PGERR on failure. + */ +static int replace_page(struct vm_area_struct *vma, struct page *page, + struct page *kpage, pte_t orig_pte) +{ + struct mm_struct *mm = vma->vm_mm; + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + pte_t *ptep; + spinlock_t *ptl; + pte_t entry; + + unsigned long addr; + int err = MERGE_ERR_PGERR; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ + + addr = page_address_in_vma(page, vma); + if (addr == -EFAULT) + goto out; + + pgd = pgd_offset(mm, addr); + if (!pgd_present(*pgd)) + goto out; + + p4d = p4d_offset(pgd, addr); + pud = pud_offset(p4d, addr); + if (!pud_present(*pud)) + goto out; + + pmd = pmd_offset(pud, addr); + BUG_ON(pmd_trans_huge(*pmd)); + if (!pmd_present(*pmd)) + goto out; + + mmun_start = addr; + mmun_end = addr + PAGE_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + + ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); + if (!pte_same(*ptep, orig_pte)) { + pte_unmap_unlock(ptep, ptl); + goto out_mn; + } + + flush_cache_page(vma, addr, pte_pfn(*ptep)); + ptep_clear_flush_notify(vma, addr, ptep); + entry = mk_pte(kpage, vma->vm_page_prot); + + /* special treatment is needed for zero_page */ + if ((page_to_pfn(kpage) == uksm_zero_pfn) || + (page_to_pfn(kpage) == zero_pfn)) { + entry = pte_mkspecial(entry); + dec_mm_counter(mm, MM_ANONPAGES); + inc_zone_page_state(page, NR_UKSM_ZERO_PAGES); + } else { + get_page(kpage); + page_add_anon_rmap(kpage, vma, addr, false); + } + + set_pte_at_notify(mm, addr, ptep, entry); + + page_remove_rmap(page, false); + if (!page_mapped(page)) + try_to_free_swap(page); + put_page(page); + + pte_unmap_unlock(ptep, ptl); + err = 0; +out_mn: + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); +out: + return err; +} + + +/** + * Fully hash a page with HASH_STRENGTH_MAX return a non-zero hash value. The + * zero hash value at HASH_STRENGTH_MAX is used to indicated that its + * hash_max member has not been calculated. + * + * @page The page needs to be hashed + * @hash_old The hash value calculated with current hash strength + * + * return the new hash value calculated at HASH_STRENGTH_MAX + */ +static inline u32 page_hash_max(struct page *page, u32 hash_old) +{ + u32 hash_max = 0; + void *addr; + + addr = kmap_atomic(page); + hash_max = delta_hash(addr, hash_strength, + HASH_STRENGTH_MAX, hash_old); + + kunmap_atomic(addr); + + if (!hash_max) + hash_max = 1; + + inc_rshash_neg(HASH_STRENGTH_MAX - hash_strength); + return hash_max; +} + +/* + * We compare the hash again, to ensure that it is really a hash collision + * instead of being caused by page write. + */ +static inline int check_collision(struct rmap_item *rmap_item, + u32 hash) +{ + int err; + struct page *page = rmap_item->page; + + /* if this rmap_item has already been hash_maxed, then the collision + * must appears in the second-level rbtree search. In this case we check + * if its hash_max value has been changed. Otherwise, the collision + * happens in the first-level rbtree search, so we check against it's + * current hash value. + */ + if (rmap_item->hash_max) { + inc_rshash_neg(memcmp_cost); + inc_rshash_neg(HASH_STRENGTH_MAX - hash_strength); + + if (rmap_item->hash_max == page_hash_max(page, hash)) + err = MERGE_ERR_COLLI; + else + err = MERGE_ERR_CHANGED; + } else { + inc_rshash_neg(memcmp_cost + hash_strength); + + if (page_hash(page, hash_strength, 0) == hash) + err = MERGE_ERR_COLLI; + else + err = MERGE_ERR_CHANGED; + } + + return err; +} + +/** + * Try to merge a rmap_item.page with a kpage in stable node. kpage must + * already be a ksm page. + * + * @return 0 if the pages were merged, -EFAULT otherwise. + */ +static int try_to_merge_with_uksm_page(struct rmap_item *rmap_item, + struct page *kpage, u32 hash) +{ + struct vm_area_struct *vma = rmap_item->slot->vma; + struct mm_struct *mm = vma->vm_mm; + pte_t orig_pte = __pte(0); + int err = MERGE_ERR_PGERR; + struct page *page; + + if (uksm_test_exit(mm)) + goto out; + + page = rmap_item->page; + + if (page == kpage) { /* ksm page forked */ + err = 0; + goto out; + } + + /* + * We need the page lock to read a stable PageSwapCache in + * write_protect_page(). We use trylock_page() instead of + * lock_page() because we don't want to wait here - we + * prefer to continue scanning and merging different pages, + * then come back to this page when it is unlocked. + */ + if (!trylock_page(page)) + goto out; + + if (!PageAnon(page) || !PageKsm(kpage)) + goto out_unlock; + + if (PageTransCompound(page)) { + err = split_huge_page(page); + if (err) + goto out_unlock; + } + + /* + * If this anonymous page is mapped only here, its pte may need + * to be write-protected. If it's mapped elsewhere, all of its + * ptes are necessarily already write-protected. But in either + * case, we need to lock and check page_count is not raised. + */ + if (write_protect_page(vma, page, &orig_pte, NULL) == 0) { + if (pages_identical(page, kpage)) + err = replace_page(vma, page, kpage, orig_pte); + else + err = check_collision(rmap_item, hash); + } + + if ((vma->vm_flags & VM_LOCKED) && kpage && !err) { + munlock_vma_page(page); + if (!PageMlocked(kpage)) { + unlock_page(page); + lock_page(kpage); + mlock_vma_page(kpage); + page = kpage; /* for final unlock */ + } + } + +out_unlock: + unlock_page(page); +out: + return err; +} + + + +/** + * If two pages fail to merge in try_to_merge_two_pages, then we have a chance + * to restore a page mapping that has been changed in try_to_merge_two_pages. + * + * @return 0 on success. + */ +static int restore_uksm_page_pte(struct vm_area_struct *vma, unsigned long addr, + pte_t orig_pte, pte_t wprt_pte) +{ + struct mm_struct *mm = vma->vm_mm; + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + pte_t *ptep; + spinlock_t *ptl; + + int err = -EFAULT; + + pgd = pgd_offset(mm, addr); + if (!pgd_present(*pgd)) + goto out; + + p4d = p4d_offset(pgd, addr); + pud = pud_offset(p4d, addr); + if (!pud_present(*pud)) + goto out; + + pmd = pmd_offset(pud, addr); + if (!pmd_present(*pmd)) + goto out; + + ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); + if (!pte_same(*ptep, wprt_pte)) { + /* already copied, let it be */ + pte_unmap_unlock(ptep, ptl); + goto out; + } + + /* + * Good boy, still here. When we still get the ksm page, it does not + * return to the free page pool, there is no way that a pte was changed + * to other page and gets back to this page. And remind that ksm page + * do not reuse in do_wp_page(). So it's safe to restore the original + * pte. + */ + flush_cache_page(vma, addr, pte_pfn(*ptep)); + ptep_clear_flush_notify(vma, addr, ptep); + set_pte_at_notify(mm, addr, ptep, orig_pte); + + pte_unmap_unlock(ptep, ptl); + err = 0; +out: + return err; +} + +/** + * try_to_merge_two_pages() - take two identical pages and prepare + * them to be merged into one page(rmap_item->page) + * + * @return 0 if we successfully merged two identical pages into + * one ksm page. MERGE_ERR_COLLI if it's only a hash collision + * search in rbtree. MERGE_ERR_CHANGED if rmap_item has been + * changed since it's hashed. MERGE_ERR_PGERR otherwise. + * + */ +static int try_to_merge_two_pages(struct rmap_item *rmap_item, + struct rmap_item *tree_rmap_item, + u32 hash) +{ + pte_t orig_pte1 = __pte(0), orig_pte2 = __pte(0); + pte_t wprt_pte1 = __pte(0), wprt_pte2 = __pte(0); + struct vm_area_struct *vma1 = rmap_item->slot->vma; + struct vm_area_struct *vma2 = tree_rmap_item->slot->vma; + struct page *page = rmap_item->page; + struct page *tree_page = tree_rmap_item->page; + int err = MERGE_ERR_PGERR; + struct address_space *saved_mapping; + + + if (rmap_item->page == tree_rmap_item->page) + goto out; + + if (!trylock_page(page)) + goto out; + + if (!PageAnon(page)) + goto out_unlock; + + if (PageTransCompound(page)) { + err = split_huge_page(page); + if (err) + goto out_unlock; + } + + if (write_protect_page(vma1, page, &wprt_pte1, &orig_pte1) != 0) { + unlock_page(page); + goto out; + } + + /* + * While we hold page lock, upgrade page from + * PageAnon+anon_vma to PageKsm+NULL stable_node: + * stable_tree_insert() will update stable_node. + */ + saved_mapping = page->mapping; + set_page_stable_node(page, NULL); + mark_page_accessed(page); + if (!PageDirty(page)) + SetPageDirty(page); + + unlock_page(page); + + if (!trylock_page(tree_page)) + goto restore_out; + + if (!PageAnon(tree_page)) { + unlock_page(tree_page); + goto restore_out; + } + + if (PageTransCompound(tree_page)) { + err = split_huge_page(tree_page); + if (err) { + unlock_page(tree_page); + goto restore_out; + } + } + + if (write_protect_page(vma2, tree_page, &wprt_pte2, &orig_pte2) != 0) { + unlock_page(tree_page); + goto restore_out; + } + + if (pages_identical(page, tree_page)) { + err = replace_page(vma2, tree_page, page, wprt_pte2); + if (err) { + unlock_page(tree_page); + goto restore_out; + } + + if ((vma2->vm_flags & VM_LOCKED)) { + munlock_vma_page(tree_page); + if (!PageMlocked(page)) { + unlock_page(tree_page); + lock_page(page); + mlock_vma_page(page); + tree_page = page; /* for final unlock */ + } + } + + unlock_page(tree_page); + + goto out; /* success */ + + } else { + if (tree_rmap_item->hash_max && + tree_rmap_item->hash_max == rmap_item->hash_max) { + err = MERGE_ERR_COLLI_MAX; + } else if (page_hash(page, hash_strength, 0) == + page_hash(tree_page, hash_strength, 0)) { + inc_rshash_neg(memcmp_cost + hash_strength * 2); + err = MERGE_ERR_COLLI; + } else { + err = MERGE_ERR_CHANGED; + } + + unlock_page(tree_page); + } + +restore_out: + lock_page(page); + if (!restore_uksm_page_pte(vma1, get_rmap_addr(rmap_item), + orig_pte1, wprt_pte1)) + page->mapping = saved_mapping; + +out_unlock: + unlock_page(page); +out: + return err; +} + +static inline int hash_cmp(u32 new_val, u32 node_val) +{ + if (new_val > node_val) + return 1; + else if (new_val < node_val) + return -1; + else + return 0; +} + +static inline u32 rmap_item_hash_max(struct rmap_item *item, u32 hash) +{ + u32 hash_max = item->hash_max; + + if (!hash_max) { + hash_max = page_hash_max(item->page, hash); + + item->hash_max = hash_max; + } + + return hash_max; +} + + + +/** + * stable_tree_search() - search the stable tree for a page + * + * @item: the rmap_item we are comparing with + * @hash: the hash value of this item->page already calculated + * + * @return the page we have found, NULL otherwise. The page returned has + * been gotten. + */ +static struct page *stable_tree_search(struct rmap_item *item, u32 hash) +{ + struct rb_node *node = root_stable_treep->rb_node; + struct tree_node *tree_node; + unsigned long hash_max; + struct page *page = item->page; + struct stable_node *stable_node; + + stable_node = page_stable_node(page); + if (stable_node) { + /* ksm page forked, that is + * if (PageKsm(page) && !in_stable_tree(rmap_item)) + * it's actually gotten once outside. + */ + get_page(page); + return page; + } + + while (node) { + int cmp; + + tree_node = rb_entry(node, struct tree_node, node); + + cmp = hash_cmp(hash, tree_node->hash); + + if (cmp < 0) + node = node->rb_left; + else if (cmp > 0) + node = node->rb_right; + else + break; + } + + if (!node) + return NULL; + + if (tree_node->count == 1) { + stable_node = rb_entry(tree_node->sub_root.rb_node, + struct stable_node, node); + BUG_ON(!stable_node); + + goto get_page_out; + } + + /* + * ok, we have to search the second + * level subtree, hash the page to a + * full strength. + */ + node = tree_node->sub_root.rb_node; + BUG_ON(!node); + hash_max = rmap_item_hash_max(item, hash); + + while (node) { + int cmp; + + stable_node = rb_entry(node, struct stable_node, node); + + cmp = hash_cmp(hash_max, stable_node->hash_max); + + if (cmp < 0) + node = node->rb_left; + else if (cmp > 0) + node = node->rb_right; + else + goto get_page_out; + } + + return NULL; + +get_page_out: + page = get_uksm_page(stable_node, 1, 1); + return page; +} + +static int try_merge_rmap_item(struct rmap_item *item, + struct page *kpage, + struct page *tree_page) +{ + struct vm_area_struct *vma = item->slot->vma; + struct page_vma_mapped_walk pvmw = { + .page = kpage, + .vma = vma, + }; + + pvmw.address = get_rmap_addr(item); + if (!page_vma_mapped_walk(&pvmw)) + return 0; + + if (pte_write(*pvmw.pte)) { + /* has changed, abort! */ + page_vma_mapped_walk_done(&pvmw); + return 0; + } + + get_page(tree_page); + page_add_anon_rmap(tree_page, vma, pvmw.address, false); + + flush_cache_page(vma, pvmw.address, page_to_pfn(kpage)); + ptep_clear_flush_notify(vma, pvmw.address, pvmw.pte); + set_pte_at_notify(vma->vm_mm, pvmw.address, pvmw.pte, + mk_pte(tree_page, vma->vm_page_prot)); + + page_remove_rmap(kpage, false); + put_page(kpage); + + page_vma_mapped_walk_done(&pvmw); + + return 1; +} + +/** + * try_to_merge_with_stable_page() - when two rmap_items need to be inserted + * into stable tree, the page was found to be identical to a stable ksm page, + * this is the last chance we can merge them into one. + * + * @item1: the rmap_item holding the page which we wanted to insert + * into stable tree. + * @item2: the other rmap_item we found when unstable tree search + * @oldpage: the page currently mapped by the two rmap_items + * @tree_page: the page we found identical in stable tree node + * @success1: return if item1 is successfully merged + * @success2: return if item2 is successfully merged + */ +static void try_merge_with_stable(struct rmap_item *item1, + struct rmap_item *item2, + struct page **kpage, + struct page *tree_page, + int *success1, int *success2) +{ + struct vm_area_struct *vma1 = item1->slot->vma; + struct vm_area_struct *vma2 = item2->slot->vma; + *success1 = 0; + *success2 = 0; + + if (unlikely(*kpage == tree_page)) { + /* I don't think this can really happen */ + pr_warn("UKSM: unexpected condition detected in " + "%s -- *kpage == tree_page !\n", __func__); + *success1 = 1; + *success2 = 1; + return; + } + + if (!PageAnon(*kpage) || !PageKsm(*kpage)) + goto failed; + + if (!trylock_page(tree_page)) + goto failed; + + /* If the oldpage is still ksm and still pointed + * to in the right place, and still write protected, + * we are confident it's not changed, no need to + * memcmp anymore. + * be ware, we cannot take nested pte locks, + * deadlock risk. + */ + if (!try_merge_rmap_item(item1, *kpage, tree_page)) + goto unlock_failed; + + /* ok, then vma2, remind that pte1 already set */ + if (!try_merge_rmap_item(item2, *kpage, tree_page)) + goto success_1; + + *success2 = 1; +success_1: + *success1 = 1; + + + if ((*success1 && vma1->vm_flags & VM_LOCKED) || + (*success2 && vma2->vm_flags & VM_LOCKED)) { + munlock_vma_page(*kpage); + if (!PageMlocked(tree_page)) + mlock_vma_page(tree_page); + } + + /* + * We do not need oldpage any more in the caller, so can break the lock + * now. + */ + unlock_page(*kpage); + *kpage = tree_page; /* Get unlocked outside. */ + return; + +unlock_failed: + unlock_page(tree_page); +failed: + return; +} + +static inline void stable_node_hash_max(struct stable_node *node, + struct page *page, u32 hash) +{ + u32 hash_max = node->hash_max; + + if (!hash_max) { + hash_max = page_hash_max(page, hash); + node->hash_max = hash_max; + } +} + +static inline +struct stable_node *new_stable_node(struct tree_node *tree_node, + struct page *kpage, u32 hash_max) +{ + struct stable_node *new_stable_node; + + new_stable_node = alloc_stable_node(); + if (!new_stable_node) + return NULL; + + new_stable_node->kpfn = page_to_pfn(kpage); + new_stable_node->hash_max = hash_max; + new_stable_node->tree_node = tree_node; + set_page_stable_node(kpage, new_stable_node); + + return new_stable_node; +} + +static inline +struct stable_node *first_level_insert(struct tree_node *tree_node, + struct rmap_item *rmap_item, + struct rmap_item *tree_rmap_item, + struct page **kpage, u32 hash, + int *success1, int *success2) +{ + int cmp; + struct page *tree_page; + u32 hash_max = 0; + struct stable_node *stable_node, *new_snode; + struct rb_node *parent = NULL, **new; + + /* this tree node contains no sub-tree yet */ + stable_node = rb_entry(tree_node->sub_root.rb_node, + struct stable_node, node); + + tree_page = get_uksm_page(stable_node, 1, 0); + if (tree_page) { + cmp = memcmp_pages(*kpage, tree_page, 1); + if (!cmp) { + try_merge_with_stable(rmap_item, tree_rmap_item, kpage, + tree_page, success1, success2); + put_page(tree_page); + if (!*success1 && !*success2) + goto failed; + + return stable_node; + + } else { + /* + * collision in first level try to create a subtree. + * A new node need to be created. + */ + put_page(tree_page); + + stable_node_hash_max(stable_node, tree_page, + tree_node->hash); + hash_max = rmap_item_hash_max(rmap_item, hash); + cmp = hash_cmp(hash_max, stable_node->hash_max); + + parent = &stable_node->node; + if (cmp < 0) + new = &parent->rb_left; + else if (cmp > 0) + new = &parent->rb_right; + else + goto failed; + } + + } else { + /* the only stable_node deleted, we reuse its tree_node. + */ + parent = NULL; + new = &tree_node->sub_root.rb_node; + } + + new_snode = new_stable_node(tree_node, *kpage, hash_max); + if (!new_snode) + goto failed; + + rb_link_node(&new_snode->node, parent, new); + rb_insert_color(&new_snode->node, &tree_node->sub_root); + tree_node->count++; + *success1 = *success2 = 1; + + return new_snode; + +failed: + return NULL; +} + +static inline +struct stable_node *stable_subtree_insert(struct tree_node *tree_node, + struct rmap_item *rmap_item, + struct rmap_item *tree_rmap_item, + struct page **kpage, u32 hash, + int *success1, int *success2) +{ + struct page *tree_page; + u32 hash_max; + struct stable_node *stable_node, *new_snode; + struct rb_node *parent, **new; + +research: + parent = NULL; + new = &tree_node->sub_root.rb_node; + BUG_ON(!*new); + hash_max = rmap_item_hash_max(rmap_item, hash); + while (*new) { + int cmp; + + stable_node = rb_entry(*new, struct stable_node, node); + + cmp = hash_cmp(hash_max, stable_node->hash_max); + + if (cmp < 0) { + parent = *new; + new = &parent->rb_left; + } else if (cmp > 0) { + parent = *new; + new = &parent->rb_right; + } else { + tree_page = get_uksm_page(stable_node, 1, 0); + if (tree_page) { + cmp = memcmp_pages(*kpage, tree_page, 1); + if (!cmp) { + try_merge_with_stable(rmap_item, + tree_rmap_item, kpage, + tree_page, success1, success2); + + put_page(tree_page); + if (!*success1 && !*success2) + goto failed; + /* + * successfully merged with a stable + * node + */ + return stable_node; + } else { + put_page(tree_page); + goto failed; + } + } else { + /* + * stable node may be deleted, + * and subtree maybe + * restructed, cannot + * continue, research it. + */ + if (tree_node->count) { + goto research; + } else { + /* reuse the tree node*/ + parent = NULL; + new = &tree_node->sub_root.rb_node; + } + } + } + } + + new_snode = new_stable_node(tree_node, *kpage, hash_max); + if (!new_snode) + goto failed; + + rb_link_node(&new_snode->node, parent, new); + rb_insert_color(&new_snode->node, &tree_node->sub_root); + tree_node->count++; + *success1 = *success2 = 1; + + return new_snode; + +failed: + return NULL; +} + + +/** + * stable_tree_insert() - try to insert a merged page in unstable tree to + * the stable tree + * + * @kpage: the page need to be inserted + * @hash: the current hash of this page + * @rmap_item: the rmap_item being scanned + * @tree_rmap_item: the rmap_item found on unstable tree + * @success1: return if rmap_item is merged + * @success2: return if tree_rmap_item is merged + * + * @return the stable_node on stable tree if at least one + * rmap_item is inserted into stable tree, NULL + * otherwise. + */ +static struct stable_node * +stable_tree_insert(struct page **kpage, u32 hash, + struct rmap_item *rmap_item, + struct rmap_item *tree_rmap_item, + int *success1, int *success2) +{ + struct rb_node **new = &root_stable_treep->rb_node; + struct rb_node *parent = NULL; + struct stable_node *stable_node; + struct tree_node *tree_node; + u32 hash_max = 0; + + *success1 = *success2 = 0; + + while (*new) { + int cmp; + + tree_node = rb_entry(*new, struct tree_node, node); + + cmp = hash_cmp(hash, tree_node->hash); + + if (cmp < 0) { + parent = *new; + new = &parent->rb_left; + } else if (cmp > 0) { + parent = *new; + new = &parent->rb_right; + } else + break; + } + + if (*new) { + if (tree_node->count == 1) { + stable_node = first_level_insert(tree_node, rmap_item, + tree_rmap_item, kpage, + hash, success1, success2); + } else { + stable_node = stable_subtree_insert(tree_node, + rmap_item, tree_rmap_item, kpage, + hash, success1, success2); + } + } else { + + /* no tree node found */ + tree_node = alloc_tree_node(stable_tree_node_listp); + if (!tree_node) { + stable_node = NULL; + goto out; + } + + stable_node = new_stable_node(tree_node, *kpage, hash_max); + if (!stable_node) { + free_tree_node(tree_node); + goto out; + } + + tree_node->hash = hash; + rb_link_node(&tree_node->node, parent, new); + rb_insert_color(&tree_node->node, root_stable_treep); + parent = NULL; + new = &tree_node->sub_root.rb_node; + + rb_link_node(&stable_node->node, parent, new); + rb_insert_color(&stable_node->node, &tree_node->sub_root); + tree_node->count++; + *success1 = *success2 = 1; + } + +out: + return stable_node; +} + + +/** + * get_tree_rmap_item_page() - try to get the page and lock the mmap_sem + * + * @return 0 on success, -EBUSY if unable to lock the mmap_sem, + * -EINVAL if the page mapping has been changed. + */ +static inline int get_tree_rmap_item_page(struct rmap_item *tree_rmap_item) +{ + int err; + + err = get_mergeable_page_lock_mmap(tree_rmap_item); + + if (err == -EINVAL) { + /* its page map has been changed, remove it */ + remove_rmap_item_from_tree(tree_rmap_item); + } + + /* The page is gotten and mmap_sem is locked now. */ + return err; +} + + +/** + * unstable_tree_search_insert() - search an unstable tree rmap_item with the + * same hash value. Get its page and trylock the mmap_sem + */ +static inline +struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, + u32 hash) + +{ + struct rb_node **new = &root_unstable_tree.rb_node; + struct rb_node *parent = NULL; + struct tree_node *tree_node; + u32 hash_max; + struct rmap_item *tree_rmap_item; + + while (*new) { + int cmp; + + tree_node = rb_entry(*new, struct tree_node, node); + + cmp = hash_cmp(hash, tree_node->hash); + + if (cmp < 0) { + parent = *new; + new = &parent->rb_left; + } else if (cmp > 0) { + parent = *new; + new = &parent->rb_right; + } else + break; + } + + if (*new) { + /* got the tree_node */ + if (tree_node->count == 1) { + tree_rmap_item = rb_entry(tree_node->sub_root.rb_node, + struct rmap_item, node); + BUG_ON(!tree_rmap_item); + + goto get_page_out; + } + + /* well, search the collision subtree */ + new = &tree_node->sub_root.rb_node; + BUG_ON(!*new); + hash_max = rmap_item_hash_max(rmap_item, hash); + + while (*new) { + int cmp; + + tree_rmap_item = rb_entry(*new, struct rmap_item, + node); + + cmp = hash_cmp(hash_max, tree_rmap_item->hash_max); + parent = *new; + if (cmp < 0) + new = &parent->rb_left; + else if (cmp > 0) + new = &parent->rb_right; + else + goto get_page_out; + } + } else { + /* alloc a new tree_node */ + tree_node = alloc_tree_node(&unstable_tree_node_list); + if (!tree_node) + return NULL; + + tree_node->hash = hash; + rb_link_node(&tree_node->node, parent, new); + rb_insert_color(&tree_node->node, &root_unstable_tree); + parent = NULL; + new = &tree_node->sub_root.rb_node; + } + + /* did not found even in sub-tree */ + rmap_item->tree_node = tree_node; + rmap_item->address |= UNSTABLE_FLAG; + rmap_item->hash_round = uksm_hash_round; + rb_link_node(&rmap_item->node, parent, new); + rb_insert_color(&rmap_item->node, &tree_node->sub_root); + + uksm_pages_unshared++; + return NULL; + +get_page_out: + if (tree_rmap_item->page == rmap_item->page) + return NULL; + + if (get_tree_rmap_item_page(tree_rmap_item)) + return NULL; + + return tree_rmap_item; +} + +static void hold_anon_vma(struct rmap_item *rmap_item, + struct anon_vma *anon_vma) +{ + rmap_item->anon_vma = anon_vma; + get_anon_vma(anon_vma); +} + + +/** + * stable_tree_append() - append a rmap_item to a stable node. Deduplication + * ratio statistics is done in this function. + * + */ +static void stable_tree_append(struct rmap_item *rmap_item, + struct stable_node *stable_node, int logdedup) +{ + struct node_vma *node_vma = NULL, *new_node_vma, *node_vma_cont = NULL; + unsigned long key = (unsigned long)rmap_item->slot; + unsigned long factor = rmap_item->slot->rung->step; + + BUG_ON(!stable_node); + rmap_item->address |= STABLE_FLAG; + + if (hlist_empty(&stable_node->hlist)) { + uksm_pages_shared++; + goto node_vma_new; + } else { + uksm_pages_sharing++; + } + + hlist_for_each_entry(node_vma, &stable_node->hlist, hlist) { + if (node_vma->key >= key) + break; + + if (logdedup) { + node_vma->slot->pages_bemerged += factor; + if (list_empty(&node_vma->slot->dedup_list)) + list_add(&node_vma->slot->dedup_list, + &vma_slot_dedup); + } + } + + if (node_vma) { + if (node_vma->key == key) { + node_vma_cont = hlist_entry_safe(node_vma->hlist.next, struct node_vma, hlist); + goto node_vma_ok; + } else if (node_vma->key > key) { + node_vma_cont = node_vma; + } + } + +node_vma_new: + /* no same vma already in node, alloc a new node_vma */ + new_node_vma = alloc_node_vma(); + BUG_ON(!new_node_vma); + new_node_vma->head = stable_node; + new_node_vma->slot = rmap_item->slot; + + if (!node_vma) { + hlist_add_head(&new_node_vma->hlist, &stable_node->hlist); + } else if (node_vma->key != key) { + if (node_vma->key < key) + hlist_add_behind(&new_node_vma->hlist, &node_vma->hlist); + else { + hlist_add_before(&new_node_vma->hlist, + &node_vma->hlist); + } + + } + node_vma = new_node_vma; + +node_vma_ok: /* ok, ready to add to the list */ + rmap_item->head = node_vma; + hlist_add_head(&rmap_item->hlist, &node_vma->rmap_hlist); + hold_anon_vma(rmap_item, rmap_item->slot->vma->anon_vma); + if (logdedup) { + rmap_item->slot->pages_merged++; + if (node_vma_cont) { + node_vma = node_vma_cont; + hlist_for_each_entry_continue(node_vma, hlist) { + node_vma->slot->pages_bemerged += factor; + if (list_empty(&node_vma->slot->dedup_list)) + list_add(&node_vma->slot->dedup_list, + &vma_slot_dedup); + } + } + } +} + +/* + * We use break_ksm to break COW on a ksm page: it's a stripped down + * + * if (get_user_pages(addr, 1, 1, 1, &page, NULL) == 1) + * put_page(page); + * + * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, + * in case the application has unmapped and remapped mm,addr meanwhile. + * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP + * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. + */ +static int break_ksm(struct vm_area_struct *vma, unsigned long addr) +{ + struct page *page; + int ret = 0; + + do { + cond_resched(); + page = follow_page(vma, addr, FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE); + if (IS_ERR_OR_NULL(page)) + break; + if (PageKsm(page)) { + ret = handle_mm_fault(vma, addr, + FAULT_FLAG_WRITE | FAULT_FLAG_REMOTE); + } else + ret = VM_FAULT_WRITE; + put_page(page); + } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | VM_FAULT_OOM))); + /* + * We must loop because handle_mm_fault() may back out if there's + * any difficulty e.g. if pte accessed bit gets updated concurrently. + * + * VM_FAULT_WRITE is what we have been hoping for: it indicates that + * COW has been broken, even if the vma does not permit VM_WRITE; + * but note that a concurrent fault might break PageKsm for us. + * + * VM_FAULT_SIGBUS could occur if we race with truncation of the + * backing file, which also invalidates anonymous pages: that's + * okay, that truncation will have unmapped the PageKsm for us. + * + * VM_FAULT_OOM: at the time of writing (late July 2009), setting + * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the + * current task has TIF_MEMDIE set, and will be OOM killed on return + * to user; and ksmd, having no mm, would never be chosen for that. + * + * But if the mm is in a limited mem_cgroup, then the fault may fail + * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and + * even ksmd can fail in this way - though it's usually breaking ksm + * just to undo a merge it made a moment before, so unlikely to oom. + * + * That's a pity: we might therefore have more kernel pages allocated + * than we're counting as nodes in the stable tree; but uksm_do_scan + * will retry to break_cow on each pass, so should recover the page + * in due course. The important thing is to not let VM_MERGEABLE + * be cleared while any such pages might remain in the area. + */ + return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; +} + +static void break_cow(struct rmap_item *rmap_item) +{ + struct vm_area_struct *vma = rmap_item->slot->vma; + struct mm_struct *mm = vma->vm_mm; + unsigned long addr = get_rmap_addr(rmap_item); + + if (uksm_test_exit(mm)) + goto out; + + break_ksm(vma, addr); +out: + return; +} + +/* + * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather + * than check every pte of a given vma, the locking doesn't quite work for + * that - an rmap_item is assigned to the stable tree after inserting ksm + * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing + * rmap_items from parent to child at fork time (so as not to waste time + * if exit comes before the next scan reaches it). + * + * Similarly, although we'd like to remove rmap_items (so updating counts + * and freeing memory) when unmerging an area, it's easier to leave that + * to the next pass of ksmd - consider, for example, how ksmd might be + * in cmp_and_merge_page on one of the rmap_items we would be removing. + */ +inline int unmerge_uksm_pages(struct vm_area_struct *vma, + unsigned long start, unsigned long end) +{ + unsigned long addr; + int err = 0; + + for (addr = start; addr < end && !err; addr += PAGE_SIZE) { + if (uksm_test_exit(vma->vm_mm)) + break; + if (signal_pending(current)) + err = -ERESTARTSYS; + else + err = break_ksm(vma, addr); + } + return err; +} + +static inline void inc_uksm_pages_scanned(void) +{ + u64 delta; + + + if (uksm_pages_scanned == U64_MAX) { + encode_benefit(); + + delta = uksm_pages_scanned >> pages_scanned_base; + + if (CAN_OVERFLOW_U64(pages_scanned_stored, delta)) { + pages_scanned_stored >>= 1; + delta >>= 1; + pages_scanned_base++; + } + + pages_scanned_stored += delta; + + uksm_pages_scanned = uksm_pages_scanned_last = 0; + } + + uksm_pages_scanned++; +} + +static inline int find_zero_page_hash(int strength, u32 hash) +{ + return (zero_hash_table[strength] == hash); +} + +static +int cmp_and_merge_zero_page(struct vm_area_struct *vma, struct page *page) +{ + struct page *zero_page = empty_uksm_zero_page; + struct mm_struct *mm = vma->vm_mm; + pte_t orig_pte = __pte(0); + int err = -EFAULT; + + if (uksm_test_exit(mm)) + goto out; + + if (!trylock_page(page)) + goto out; + + if (!PageAnon(page)) + goto out_unlock; + + if (PageTransCompound(page)) { + err = split_huge_page(page); + if (err) + goto out_unlock; + } + + if (write_protect_page(vma, page, &orig_pte, 0) == 0) { + if (is_page_full_zero(page)) + err = replace_page(vma, page, zero_page, orig_pte); + } + +out_unlock: + unlock_page(page); +out: + return err; +} + +/* + * cmp_and_merge_page() - first see if page can be merged into the stable + * tree; if not, compare hash to previous and if it's the same, see if page + * can be inserted into the unstable tree, or merged with a page already there + * and both transferred to the stable tree. + * + * @page: the page that we are searching identical page to. + * @rmap_item: the reverse mapping into the virtual address of this page + */ +static void cmp_and_merge_page(struct rmap_item *rmap_item, u32 hash) +{ + struct rmap_item *tree_rmap_item; + struct page *page; + struct page *kpage = NULL; + u32 hash_max; + int err; + unsigned int success1, success2; + struct stable_node *snode; + int cmp; + struct rb_node *parent = NULL, **new; + + remove_rmap_item_from_tree(rmap_item); + page = rmap_item->page; + + /* We first start with searching the page inside the stable tree */ + kpage = stable_tree_search(rmap_item, hash); + if (kpage) { + err = try_to_merge_with_uksm_page(rmap_item, kpage, + hash); + if (!err) { + /* + * The page was successfully merged, add + * its rmap_item to the stable tree. + * page lock is needed because it's + * racing with try_to_unmap_ksm(), etc. + */ + lock_page(kpage); + snode = page_stable_node(kpage); + stable_tree_append(rmap_item, snode, 1); + unlock_page(kpage); + put_page(kpage); + return; /* success */ + } + put_page(kpage); + + /* + * if it's a collision and it has been search in sub-rbtree + * (hash_max != 0), we want to abort, because if it is + * successfully merged in unstable tree, the collision trends to + * happen again. + */ + if (err == MERGE_ERR_COLLI && rmap_item->hash_max) + return; + } + + tree_rmap_item = + unstable_tree_search_insert(rmap_item, hash); + if (tree_rmap_item) { + err = try_to_merge_two_pages(rmap_item, tree_rmap_item, hash); + /* + * As soon as we merge this page, we want to remove the + * rmap_item of the page we have merged with from the unstable + * tree, and insert it instead as new node in the stable tree. + */ + if (!err) { + kpage = page; + remove_rmap_item_from_tree(tree_rmap_item); + lock_page(kpage); + snode = stable_tree_insert(&kpage, hash, + rmap_item, tree_rmap_item, + &success1, &success2); + + /* + * Do not log dedup for tree item, it's not counted as + * scanned in this round. + */ + if (success2) + stable_tree_append(tree_rmap_item, snode, 0); + + /* + * The order of these two stable append is important: + * we are scanning rmap_item. + */ + if (success1) + stable_tree_append(rmap_item, snode, 1); + + /* + * The original kpage may be unlocked inside + * stable_tree_insert() already. This page + * should be unlocked before doing + * break_cow(). + */ + unlock_page(kpage); + + if (!success1) + break_cow(rmap_item); + + if (!success2) + break_cow(tree_rmap_item); + + } else if (err == MERGE_ERR_COLLI) { + BUG_ON(tree_rmap_item->tree_node->count > 1); + + rmap_item_hash_max(tree_rmap_item, + tree_rmap_item->tree_node->hash); + + hash_max = rmap_item_hash_max(rmap_item, hash); + cmp = hash_cmp(hash_max, tree_rmap_item->hash_max); + parent = &tree_rmap_item->node; + if (cmp < 0) + new = &parent->rb_left; + else if (cmp > 0) + new = &parent->rb_right; + else + goto put_up_out; + + rmap_item->tree_node = tree_rmap_item->tree_node; + rmap_item->address |= UNSTABLE_FLAG; + rmap_item->hash_round = uksm_hash_round; + rb_link_node(&rmap_item->node, parent, new); + rb_insert_color(&rmap_item->node, + &tree_rmap_item->tree_node->sub_root); + rmap_item->tree_node->count++; + } else { + /* + * either one of the page has changed or they collide + * at the max hash, we consider them as ill items. + */ + remove_rmap_item_from_tree(tree_rmap_item); + } +put_up_out: + put_page(tree_rmap_item->page); + up_read(&tree_rmap_item->slot->vma->vm_mm->mmap_sem); + } +} + + + + +static inline unsigned long get_pool_index(struct vma_slot *slot, + unsigned long index) +{ + unsigned long pool_index; + + pool_index = (sizeof(struct rmap_list_entry *) * index) >> PAGE_SHIFT; + if (pool_index >= slot->pool_size) + BUG(); + return pool_index; +} + +static inline unsigned long index_page_offset(unsigned long index) +{ + return offset_in_page(sizeof(struct rmap_list_entry *) * index); +} + +static inline +struct rmap_list_entry *get_rmap_list_entry(struct vma_slot *slot, + unsigned long index, int need_alloc) +{ + unsigned long pool_index; + struct page *page; + void *addr; + + + pool_index = get_pool_index(slot, index); + if (!slot->rmap_list_pool[pool_index]) { + if (!need_alloc) + return NULL; + + page = alloc_page(GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN); + if (!page) + return NULL; + + slot->rmap_list_pool[pool_index] = page; + } + + addr = kmap(slot->rmap_list_pool[pool_index]); + addr += index_page_offset(index); + + return addr; +} + +static inline void put_rmap_list_entry(struct vma_slot *slot, + unsigned long index) +{ + unsigned long pool_index; + + pool_index = get_pool_index(slot, index); + BUG_ON(!slot->rmap_list_pool[pool_index]); + kunmap(slot->rmap_list_pool[pool_index]); +} + +static inline int entry_is_new(struct rmap_list_entry *entry) +{ + return !entry->item; +} + +static inline unsigned long get_index_orig_addr(struct vma_slot *slot, + unsigned long index) +{ + return slot->vma->vm_start + (index << PAGE_SHIFT); +} + +static inline unsigned long get_entry_address(struct rmap_list_entry *entry) +{ + unsigned long addr; + + if (is_addr(entry->addr)) + addr = get_clean_addr(entry->addr); + else if (entry->item) + addr = get_rmap_addr(entry->item); + else + BUG(); + + return addr; +} + +static inline struct rmap_item *get_entry_item(struct rmap_list_entry *entry) +{ + if (is_addr(entry->addr)) + return NULL; + + return entry->item; +} + +static inline void inc_rmap_list_pool_count(struct vma_slot *slot, + unsigned long index) +{ + unsigned long pool_index; + + pool_index = get_pool_index(slot, index); + BUG_ON(!slot->rmap_list_pool[pool_index]); + slot->pool_counts[pool_index]++; +} + +static inline void dec_rmap_list_pool_count(struct vma_slot *slot, + unsigned long index) +{ + unsigned long pool_index; + + pool_index = get_pool_index(slot, index); + BUG_ON(!slot->rmap_list_pool[pool_index]); + BUG_ON(!slot->pool_counts[pool_index]); + slot->pool_counts[pool_index]--; +} + +static inline int entry_has_rmap(struct rmap_list_entry *entry) +{ + return !is_addr(entry->addr) && entry->item; +} + +static inline void swap_entries(struct rmap_list_entry *entry1, + unsigned long index1, + struct rmap_list_entry *entry2, + unsigned long index2) +{ + struct rmap_list_entry tmp; + + /* swapping two new entries is meaningless */ + BUG_ON(entry_is_new(entry1) && entry_is_new(entry2)); + + tmp = *entry1; + *entry1 = *entry2; + *entry2 = tmp; + + if (entry_has_rmap(entry1)) + entry1->item->entry_index = index1; + + if (entry_has_rmap(entry2)) + entry2->item->entry_index = index2; + + if (entry_has_rmap(entry1) && !entry_has_rmap(entry2)) { + inc_rmap_list_pool_count(entry1->item->slot, index1); + dec_rmap_list_pool_count(entry1->item->slot, index2); + } else if (!entry_has_rmap(entry1) && entry_has_rmap(entry2)) { + inc_rmap_list_pool_count(entry2->item->slot, index2); + dec_rmap_list_pool_count(entry2->item->slot, index1); + } +} + +static inline void free_entry_item(struct rmap_list_entry *entry) +{ + unsigned long index; + struct rmap_item *item; + + if (!is_addr(entry->addr)) { + BUG_ON(!entry->item); + item = entry->item; + entry->addr = get_rmap_addr(item); + set_is_addr(entry->addr); + index = item->entry_index; + remove_rmap_item_from_tree(item); + dec_rmap_list_pool_count(item->slot, index); + free_rmap_item(item); + } +} + +static inline int pool_entry_boundary(unsigned long index) +{ + unsigned long linear_addr; + + linear_addr = sizeof(struct rmap_list_entry *) * index; + return index && !offset_in_page(linear_addr); +} + +static inline void try_free_last_pool(struct vma_slot *slot, + unsigned long index) +{ + unsigned long pool_index; + + pool_index = get_pool_index(slot, index); + if (slot->rmap_list_pool[pool_index] && + !slot->pool_counts[pool_index]) { + __free_page(slot->rmap_list_pool[pool_index]); + slot->rmap_list_pool[pool_index] = NULL; + slot->flags |= UKSM_SLOT_NEED_SORT; + } + +} + +static inline unsigned long vma_item_index(struct vm_area_struct *vma, + struct rmap_item *item) +{ + return (get_rmap_addr(item) - vma->vm_start) >> PAGE_SHIFT; +} + +static int within_same_pool(struct vma_slot *slot, + unsigned long i, unsigned long j) +{ + unsigned long pool_i, pool_j; + + pool_i = get_pool_index(slot, i); + pool_j = get_pool_index(slot, j); + + return (pool_i == pool_j); +} + +static void sort_rmap_entry_list(struct vma_slot *slot) +{ + unsigned long i, j; + struct rmap_list_entry *entry, *swap_entry; + + entry = get_rmap_list_entry(slot, 0, 0); + for (i = 0; i < slot->pages; ) { + + if (!entry) + goto skip_whole_pool; + + if (entry_is_new(entry)) + goto next_entry; + + if (is_addr(entry->addr)) { + entry->addr = 0; + goto next_entry; + } + + j = vma_item_index(slot->vma, entry->item); + if (j == i) + goto next_entry; + + if (within_same_pool(slot, i, j)) + swap_entry = entry + j - i; + else + swap_entry = get_rmap_list_entry(slot, j, 1); + + swap_entries(entry, i, swap_entry, j); + if (!within_same_pool(slot, i, j)) + put_rmap_list_entry(slot, j); + continue; + +skip_whole_pool: + i += PAGE_SIZE / sizeof(*entry); + if (i < slot->pages) + entry = get_rmap_list_entry(slot, i, 0); + continue; + +next_entry: + if (i >= slot->pages - 1 || + !within_same_pool(slot, i, i + 1)) { + put_rmap_list_entry(slot, i); + if (i + 1 < slot->pages) + entry = get_rmap_list_entry(slot, i + 1, 0); + } else + entry++; + i++; + continue; + } + + /* free empty pool entries which contain no rmap_item */ + /* CAN be simplied to based on only pool_counts when bug freed !!!!! */ + for (i = 0; i < slot->pool_size; i++) { + unsigned char has_rmap; + void *addr; + + if (!slot->rmap_list_pool[i]) + continue; + + has_rmap = 0; + addr = kmap(slot->rmap_list_pool[i]); + BUG_ON(!addr); + for (j = 0; j < PAGE_SIZE / sizeof(*entry); j++) { + entry = (struct rmap_list_entry *)addr + j; + if (is_addr(entry->addr)) + continue; + if (!entry->item) + continue; + has_rmap = 1; + } + kunmap(slot->rmap_list_pool[i]); + if (!has_rmap) { + BUG_ON(slot->pool_counts[i]); + __free_page(slot->rmap_list_pool[i]); + slot->rmap_list_pool[i] = NULL; + } + } + + slot->flags &= ~UKSM_SLOT_NEED_SORT; +} + +/* + * vma_fully_scanned() - if all the pages in this slot have been scanned. + */ +static inline int vma_fully_scanned(struct vma_slot *slot) +{ + return slot->pages_scanned == slot->pages; +} + +/** + * get_next_rmap_item() - Get the next rmap_item in a vma_slot according to + * its random permutation. This function is embedded with the random + * permutation index management code. + */ +static struct rmap_item *get_next_rmap_item(struct vma_slot *slot, u32 *hash) +{ + unsigned long rand_range, addr, swap_index, scan_index; + struct rmap_item *item = NULL; + struct rmap_list_entry *scan_entry, *swap_entry = NULL; + struct page *page; + + scan_index = swap_index = slot->pages_scanned % slot->pages; + + if (pool_entry_boundary(scan_index)) + try_free_last_pool(slot, scan_index - 1); + + if (vma_fully_scanned(slot)) { + if (slot->flags & UKSM_SLOT_NEED_SORT) + slot->flags |= UKSM_SLOT_NEED_RERAND; + else + slot->flags &= ~UKSM_SLOT_NEED_RERAND; + if (slot->flags & UKSM_SLOT_NEED_SORT) + sort_rmap_entry_list(slot); + } + + scan_entry = get_rmap_list_entry(slot, scan_index, 1); + if (!scan_entry) + return NULL; + + if (entry_is_new(scan_entry)) { + scan_entry->addr = get_index_orig_addr(slot, scan_index); + set_is_addr(scan_entry->addr); + } + + if (slot->flags & UKSM_SLOT_NEED_RERAND) { + rand_range = slot->pages - scan_index; + BUG_ON(!rand_range); + swap_index = scan_index + (prandom_u32() % rand_range); + } + + if (swap_index != scan_index) { + swap_entry = get_rmap_list_entry(slot, swap_index, 1); + if (entry_is_new(swap_entry)) { + swap_entry->addr = get_index_orig_addr(slot, + swap_index); + set_is_addr(swap_entry->addr); + } + swap_entries(scan_entry, scan_index, swap_entry, swap_index); + } + + addr = get_entry_address(scan_entry); + item = get_entry_item(scan_entry); + BUG_ON(addr > slot->vma->vm_end || addr < slot->vma->vm_start); + + page = follow_page(slot->vma, addr, FOLL_GET); + if (IS_ERR_OR_NULL(page)) + goto nopage; + + if (!PageAnon(page)) + goto putpage; + + /*check is zero_page pfn or uksm_zero_page*/ + if ((page_to_pfn(page) == zero_pfn) + || (page_to_pfn(page) == uksm_zero_pfn)) + goto putpage; + + flush_anon_page(slot->vma, page, addr); + flush_dcache_page(page); + + + *hash = page_hash(page, hash_strength, 1); + inc_uksm_pages_scanned(); + /*if the page content all zero, re-map to zero-page*/ + if (find_zero_page_hash(hash_strength, *hash)) { + if (!cmp_and_merge_zero_page(slot->vma, page)) { + slot->pages_merged++; + + /* For full-zero pages, no need to create rmap item */ + goto putpage; + } else { + inc_rshash_neg(memcmp_cost / 2); + } + } + + if (!item) { + item = alloc_rmap_item(); + if (item) { + /* It has already been zeroed */ + item->slot = slot; + item->address = addr; + item->entry_index = scan_index; + scan_entry->item = item; + inc_rmap_list_pool_count(slot, scan_index); + } else + goto putpage; + } + + BUG_ON(item->slot != slot); + /* the page may have changed */ + item->page = page; + put_rmap_list_entry(slot, scan_index); + if (swap_entry) + put_rmap_list_entry(slot, swap_index); + return item; + +putpage: + put_page(page); + page = NULL; +nopage: + /* no page, store addr back and free rmap_item if possible */ + free_entry_item(scan_entry); + put_rmap_list_entry(slot, scan_index); + if (swap_entry) + put_rmap_list_entry(slot, swap_index); + return NULL; +} + +static inline int in_stable_tree(struct rmap_item *rmap_item) +{ + return rmap_item->address & STABLE_FLAG; +} + +/** + * scan_vma_one_page() - scan the next page in a vma_slot. Called with + * mmap_sem locked. + */ +static noinline void scan_vma_one_page(struct vma_slot *slot) +{ + u32 hash; + struct mm_struct *mm; + struct rmap_item *rmap_item = NULL; + struct vm_area_struct *vma = slot->vma; + + mm = vma->vm_mm; + BUG_ON(!mm); + BUG_ON(!slot); + + rmap_item = get_next_rmap_item(slot, &hash); + if (!rmap_item) + goto out1; + + if (PageKsm(rmap_item->page) && in_stable_tree(rmap_item)) + goto out2; + + cmp_and_merge_page(rmap_item, hash); +out2: + put_page(rmap_item->page); +out1: + slot->pages_scanned++; + slot->this_sampled++; + if (slot->fully_scanned_round != fully_scanned_round) + scanned_virtual_pages++; + + if (vma_fully_scanned(slot)) + slot->fully_scanned_round = fully_scanned_round; +} + +static inline unsigned long rung_get_pages(struct scan_rung *rung) +{ + struct slot_tree_node *node; + + if (!rung->vma_root.rnode) + return 0; + + node = container_of(rung->vma_root.rnode, struct slot_tree_node, snode); + + return node->size; +} + +#define RUNG_SAMPLED_MIN 3 + +static inline +void uksm_calc_rung_step(struct scan_rung *rung, + unsigned long page_time, unsigned long ratio) +{ + unsigned long sampled, pages; + + /* will be fully scanned ? */ + if (!rung->cover_msecs) { + rung->step = 1; + return; + } + + sampled = rung->cover_msecs * (NSEC_PER_MSEC / TIME_RATIO_SCALE) + * ratio / page_time; + + /* + * Before we finsish a scan round and expensive per-round jobs, + * we need to have a chance to estimate the per page time. So + * the sampled number can not be too small. + */ + if (sampled < RUNG_SAMPLED_MIN) + sampled = RUNG_SAMPLED_MIN; + + pages = rung_get_pages(rung); + if (likely(pages > sampled)) + rung->step = pages / sampled; + else + rung->step = 1; +} + +static inline int step_need_recalc(struct scan_rung *rung) +{ + unsigned long pages, stepmax; + + pages = rung_get_pages(rung); + stepmax = pages / RUNG_SAMPLED_MIN; + + return pages && (rung->step > pages || + (stepmax && rung->step > stepmax)); +} + +static inline +void reset_current_scan(struct scan_rung *rung, int finished, int step_recalc) +{ + struct vma_slot *slot; + + if (finished) + rung->flags |= UKSM_RUNG_ROUND_FINISHED; + + if (step_recalc || step_need_recalc(rung)) { + uksm_calc_rung_step(rung, uksm_ema_page_time, rung->cpu_ratio); + BUG_ON(step_need_recalc(rung)); + } + + slot_iter_index = prandom_u32() % rung->step; + BUG_ON(!rung->vma_root.rnode); + slot = sradix_tree_next(&rung->vma_root, NULL, 0, slot_iter); + BUG_ON(!slot); + + rung->current_scan = slot; + rung->current_offset = slot_iter_index; +} + +static inline struct sradix_tree_root *slot_get_root(struct vma_slot *slot) +{ + return &slot->rung->vma_root; +} + +/* + * return if resetted. + */ +static int advance_current_scan(struct scan_rung *rung) +{ + unsigned short n; + struct vma_slot *slot, *next = NULL; + + BUG_ON(!rung->vma_root.num); + + slot = rung->current_scan; + n = (slot->pages - rung->current_offset) % rung->step; + slot_iter_index = rung->step - n; + next = sradix_tree_next(&rung->vma_root, slot->snode, + slot->sindex, slot_iter); + + if (next) { + rung->current_offset = slot_iter_index; + rung->current_scan = next; + return 0; + } else { + reset_current_scan(rung, 1, 0); + return 1; + } +} + +static inline void rung_rm_slot(struct vma_slot *slot) +{ + struct scan_rung *rung = slot->rung; + struct sradix_tree_root *root; + + if (rung->current_scan == slot) + advance_current_scan(rung); + + root = slot_get_root(slot); + sradix_tree_delete_from_leaf(root, slot->snode, slot->sindex); + slot->snode = NULL; + if (step_need_recalc(rung)) { + uksm_calc_rung_step(rung, uksm_ema_page_time, rung->cpu_ratio); + BUG_ON(step_need_recalc(rung)); + } + + /* In case advance_current_scan loop back to this slot again */ + if (rung->vma_root.num && rung->current_scan == slot) + reset_current_scan(slot->rung, 1, 0); +} + +static inline void rung_add_new_slots(struct scan_rung *rung, + struct vma_slot **slots, unsigned long num) +{ + int err; + struct vma_slot *slot; + unsigned long i; + struct sradix_tree_root *root = &rung->vma_root; + + err = sradix_tree_enter(root, (void **)slots, num); + BUG_ON(err); + + for (i = 0; i < num; i++) { + slot = slots[i]; + slot->rung = rung; + BUG_ON(vma_fully_scanned(slot)); + } + + if (rung->vma_root.num == num) + reset_current_scan(rung, 0, 1); +} + +static inline int rung_add_one_slot(struct scan_rung *rung, + struct vma_slot *slot) +{ + int err; + + err = sradix_tree_enter(&rung->vma_root, (void **)&slot, 1); + if (err) + return err; + + slot->rung = rung; + if (rung->vma_root.num == 1) + reset_current_scan(rung, 0, 1); + + return 0; +} + +/* + * Return true if the slot is deleted from its rung. + */ +static inline int vma_rung_enter(struct vma_slot *slot, struct scan_rung *rung) +{ + struct scan_rung *old_rung = slot->rung; + int err; + + if (old_rung == rung) + return 0; + + rung_rm_slot(slot); + err = rung_add_one_slot(rung, slot); + if (err) { + err = rung_add_one_slot(old_rung, slot); + WARN_ON(err); /* OOPS, badly OOM, we lost this slot */ + } + + return 1; +} + +static inline int vma_rung_up(struct vma_slot *slot) +{ + struct scan_rung *rung; + + rung = slot->rung; + if (slot->rung != &uksm_scan_ladder[SCAN_LADDER_SIZE-1]) + rung++; + + return vma_rung_enter(slot, rung); +} + +static inline int vma_rung_down(struct vma_slot *slot) +{ + struct scan_rung *rung; + + rung = slot->rung; + if (slot->rung != &uksm_scan_ladder[0]) + rung--; + + return vma_rung_enter(slot, rung); +} + +/** + * cal_dedup_ratio() - Calculate the deduplication ratio for this slot. + */ +static unsigned long cal_dedup_ratio(struct vma_slot *slot) +{ + unsigned long ret; + unsigned long pages; + + pages = slot->this_sampled; + if (!pages) + return 0; + + BUG_ON(slot->pages_scanned == slot->last_scanned); + + ret = slot->pages_merged; + + /* Thrashing area filtering */ + if (ret && uksm_thrash_threshold) { + if (slot->pages_cowed * 100 / slot->pages_merged + > uksm_thrash_threshold) { + ret = 0; + } else { + ret = slot->pages_merged - slot->pages_cowed; + } + } + + return ret * 100 / pages; +} + +/** + * cal_dedup_ratio() - Calculate the deduplication ratio for this slot. + */ +static unsigned long cal_dedup_ratio_old(struct vma_slot *slot) +{ + unsigned long ret; + unsigned long pages; + + pages = slot->pages; + if (!pages) + return 0; + + ret = slot->pages_bemerged; + + /* Thrashing area filtering */ + if (ret && uksm_thrash_threshold) { + if (slot->pages_cowed * 100 / slot->pages_bemerged + > uksm_thrash_threshold) { + ret = 0; + } else { + ret = slot->pages_bemerged - slot->pages_cowed; + } + } + + return ret * 100 / pages; +} + +/** + * stable_node_reinsert() - When the hash_strength has been adjusted, the + * stable tree need to be restructured, this is the function re-inserting the + * stable node. + */ +static inline void stable_node_reinsert(struct stable_node *new_node, + struct page *page, + struct rb_root *root_treep, + struct list_head *tree_node_listp, + u32 hash) +{ + struct rb_node **new = &root_treep->rb_node; + struct rb_node *parent = NULL; + struct stable_node *stable_node; + struct tree_node *tree_node; + struct page *tree_page; + int cmp; + + while (*new) { + int cmp; + + tree_node = rb_entry(*new, struct tree_node, node); + + cmp = hash_cmp(hash, tree_node->hash); + + if (cmp < 0) { + parent = *new; + new = &parent->rb_left; + } else if (cmp > 0) { + parent = *new; + new = &parent->rb_right; + } else + break; + } + + if (*new) { + /* find a stable tree node with same first level hash value */ + stable_node_hash_max(new_node, page, hash); + if (tree_node->count == 1) { + stable_node = rb_entry(tree_node->sub_root.rb_node, + struct stable_node, node); + tree_page = get_uksm_page(stable_node, 1, 0); + if (tree_page) { + stable_node_hash_max(stable_node, + tree_page, hash); + put_page(tree_page); + + /* prepare for stable node insertion */ + + cmp = hash_cmp(new_node->hash_max, + stable_node->hash_max); + parent = &stable_node->node; + if (cmp < 0) + new = &parent->rb_left; + else if (cmp > 0) + new = &parent->rb_right; + else + goto failed; + + goto add_node; + } else { + /* the only stable_node deleted, the tree node + * was not deleted. + */ + goto tree_node_reuse; + } + } + + /* well, search the collision subtree */ + new = &tree_node->sub_root.rb_node; + parent = NULL; + BUG_ON(!*new); + while (*new) { + int cmp; + + stable_node = rb_entry(*new, struct stable_node, node); + + cmp = hash_cmp(new_node->hash_max, + stable_node->hash_max); + + if (cmp < 0) { + parent = *new; + new = &parent->rb_left; + } else if (cmp > 0) { + parent = *new; + new = &parent->rb_right; + } else { + /* oh, no, still a collision */ + goto failed; + } + } + + goto add_node; + } + + /* no tree node found */ + tree_node = alloc_tree_node(tree_node_listp); + if (!tree_node) { + pr_err("UKSM: memory allocation error!\n"); + goto failed; + } else { + tree_node->hash = hash; + rb_link_node(&tree_node->node, parent, new); + rb_insert_color(&tree_node->node, root_treep); + +tree_node_reuse: + /* prepare for stable node insertion */ + parent = NULL; + new = &tree_node->sub_root.rb_node; + } + +add_node: + rb_link_node(&new_node->node, parent, new); + rb_insert_color(&new_node->node, &tree_node->sub_root); + new_node->tree_node = tree_node; + tree_node->count++; + return; + +failed: + /* This can only happen when two nodes have collided + * in two levels. + */ + new_node->tree_node = NULL; + return; +} + +static inline void free_all_tree_nodes(struct list_head *list) +{ + struct tree_node *node, *tmp; + + list_for_each_entry_safe(node, tmp, list, all_list) { + free_tree_node(node); + } +} + +/** + * stable_tree_delta_hash() - Delta hash the stable tree from previous hash + * strength to the current hash_strength. It re-structures the hole tree. + */ +static inline void stable_tree_delta_hash(u32 prev_hash_strength) +{ + struct stable_node *node, *tmp; + struct rb_root *root_new_treep; + struct list_head *new_tree_node_listp; + + stable_tree_index = (stable_tree_index + 1) % 2; + root_new_treep = &root_stable_tree[stable_tree_index]; + new_tree_node_listp = &stable_tree_node_list[stable_tree_index]; + *root_new_treep = RB_ROOT; + BUG_ON(!list_empty(new_tree_node_listp)); + + /* + * we need to be safe, the node could be removed by get_uksm_page() + */ + list_for_each_entry_safe(node, tmp, &stable_node_list, all_list) { + void *addr; + struct page *node_page; + u32 hash; + + /* + * We are completely re-structuring the stable nodes to a new + * stable tree. We don't want to touch the old tree unlinks and + * old tree_nodes. The old tree_nodes will be freed at once. + */ + node_page = get_uksm_page(node, 0, 0); + if (!node_page) + continue; + + if (node->tree_node) { + hash = node->tree_node->hash; + + addr = kmap_atomic(node_page); + + hash = delta_hash(addr, prev_hash_strength, + hash_strength, hash); + kunmap_atomic(addr); + } else { + /* + *it was not inserted to rbtree due to collision in last + *round scan. + */ + hash = page_hash(node_page, hash_strength, 0); + } + + stable_node_reinsert(node, node_page, root_new_treep, + new_tree_node_listp, hash); + put_page(node_page); + } + + root_stable_treep = root_new_treep; + free_all_tree_nodes(stable_tree_node_listp); + BUG_ON(!list_empty(stable_tree_node_listp)); + stable_tree_node_listp = new_tree_node_listp; +} + +static inline void inc_hash_strength(unsigned long delta) +{ + hash_strength += 1 << delta; + if (hash_strength > HASH_STRENGTH_MAX) + hash_strength = HASH_STRENGTH_MAX; +} + +static inline void dec_hash_strength(unsigned long delta) +{ + unsigned long change = 1 << delta; + + if (hash_strength <= change + 1) + hash_strength = 1; + else + hash_strength -= change; +} + +static inline void inc_hash_strength_delta(void) +{ + hash_strength_delta++; + if (hash_strength_delta > HASH_STRENGTH_DELTA_MAX) + hash_strength_delta = HASH_STRENGTH_DELTA_MAX; +} + +static inline unsigned long get_current_neg_ratio(void) +{ + u64 pos = benefit.pos; + u64 neg = benefit.neg; + + if (!neg) + return 0; + + if (!pos || neg > pos) + return 100; + + if (neg > div64_u64(U64_MAX, 100)) + pos = div64_u64(pos, 100); + else + neg *= 100; + + return div64_u64(neg, pos); +} + +static inline unsigned long get_current_benefit(void) +{ + u64 pos = benefit.pos; + u64 neg = benefit.neg; + u64 scanned = benefit.scanned; + + if (neg > pos) + return 0; + + return div64_u64((pos - neg), scanned); +} + +static inline int judge_rshash_direction(void) +{ + u64 current_neg_ratio, stable_benefit; + u64 current_benefit, delta = 0; + int ret = STILL; + + /* + * Try to probe a value after the boot, and in case the system + * are still for a long time. + */ + if ((fully_scanned_round & 0xFFULL) == 10) { + ret = OBSCURE; + goto out; + } + + current_neg_ratio = get_current_neg_ratio(); + + if (current_neg_ratio == 0) { + rshash_neg_cont_zero++; + if (rshash_neg_cont_zero > 2) + return GO_DOWN; + else + return STILL; + } + rshash_neg_cont_zero = 0; + + if (current_neg_ratio > 90) { + ret = GO_UP; + goto out; + } + + current_benefit = get_current_benefit(); + stable_benefit = rshash_state.stable_benefit; + + if (!stable_benefit) { + ret = OBSCURE; + goto out; + } + + if (current_benefit > stable_benefit) + delta = current_benefit - stable_benefit; + else if (current_benefit < stable_benefit) + delta = stable_benefit - current_benefit; + + delta = div64_u64(100 * delta, stable_benefit); + + if (delta > 50) { + rshash_cont_obscure++; + if (rshash_cont_obscure > 2) + return OBSCURE; + else + return STILL; + } + +out: + rshash_cont_obscure = 0; + return ret; +} + +/** + * rshash_adjust() - The main function to control the random sampling state + * machine for hash strength adapting. + * + * return true if hash_strength has changed. + */ +static inline int rshash_adjust(void) +{ + unsigned long prev_hash_strength = hash_strength; + + if (!encode_benefit()) + return 0; + + switch (rshash_state.state) { + case RSHASH_STILL: + switch (judge_rshash_direction()) { + case GO_UP: + if (rshash_state.pre_direct == GO_DOWN) + hash_strength_delta = 0; + + inc_hash_strength(hash_strength_delta); + inc_hash_strength_delta(); + rshash_state.stable_benefit = get_current_benefit(); + rshash_state.pre_direct = GO_UP; + break; + + case GO_DOWN: + if (rshash_state.pre_direct == GO_UP) + hash_strength_delta = 0; + + dec_hash_strength(hash_strength_delta); + inc_hash_strength_delta(); + rshash_state.stable_benefit = get_current_benefit(); + rshash_state.pre_direct = GO_DOWN; + break; + + case OBSCURE: + rshash_state.stable_point = hash_strength; + rshash_state.turn_point_down = hash_strength; + rshash_state.turn_point_up = hash_strength; + rshash_state.turn_benefit_down = get_current_benefit(); + rshash_state.turn_benefit_up = get_current_benefit(); + rshash_state.lookup_window_index = 0; + rshash_state.state = RSHASH_TRYDOWN; + dec_hash_strength(hash_strength_delta); + inc_hash_strength_delta(); + break; + + case STILL: + break; + default: + BUG(); + } + break; + + case RSHASH_TRYDOWN: + if (rshash_state.lookup_window_index++ % 5 == 0) + rshash_state.below_count = 0; + + if (get_current_benefit() < rshash_state.stable_benefit) + rshash_state.below_count++; + else if (get_current_benefit() > + rshash_state.turn_benefit_down) { + rshash_state.turn_point_down = hash_strength; + rshash_state.turn_benefit_down = get_current_benefit(); + } + + if (rshash_state.below_count >= 3 || + judge_rshash_direction() == GO_UP || + hash_strength == 1) { + hash_strength = rshash_state.stable_point; + hash_strength_delta = 0; + inc_hash_strength(hash_strength_delta); + inc_hash_strength_delta(); + rshash_state.lookup_window_index = 0; + rshash_state.state = RSHASH_TRYUP; + hash_strength_delta = 0; + } else { + dec_hash_strength(hash_strength_delta); + inc_hash_strength_delta(); + } + break; + + case RSHASH_TRYUP: + if (rshash_state.lookup_window_index++ % 5 == 0) + rshash_state.below_count = 0; + + if (get_current_benefit() < rshash_state.turn_benefit_down) + rshash_state.below_count++; + else if (get_current_benefit() > rshash_state.turn_benefit_up) { + rshash_state.turn_point_up = hash_strength; + rshash_state.turn_benefit_up = get_current_benefit(); + } + + if (rshash_state.below_count >= 3 || + judge_rshash_direction() == GO_DOWN || + hash_strength == HASH_STRENGTH_MAX) { + hash_strength = rshash_state.turn_benefit_up > + rshash_state.turn_benefit_down ? + rshash_state.turn_point_up : + rshash_state.turn_point_down; + + rshash_state.state = RSHASH_PRE_STILL; + } else { + inc_hash_strength(hash_strength_delta); + inc_hash_strength_delta(); + } + + break; + + case RSHASH_NEW: + case RSHASH_PRE_STILL: + rshash_state.stable_benefit = get_current_benefit(); + rshash_state.state = RSHASH_STILL; + hash_strength_delta = 0; + break; + default: + BUG(); + } + + /* rshash_neg = rshash_pos = 0; */ + reset_benefit(); + + if (prev_hash_strength != hash_strength) + stable_tree_delta_hash(prev_hash_strength); + + return prev_hash_strength != hash_strength; +} + +/** + * round_update_ladder() - The main function to do update of all the + * adjustments whenever a scan round is finished. + */ +static noinline void round_update_ladder(void) +{ + int i; + unsigned long dedup; + struct vma_slot *slot, *tmp_slot; + + for (i = 0; i < SCAN_LADDER_SIZE; i++) + uksm_scan_ladder[i].flags &= ~UKSM_RUNG_ROUND_FINISHED; + + list_for_each_entry_safe(slot, tmp_slot, &vma_slot_dedup, dedup_list) { + + /* slot may be rung_rm_slot() when mm exits */ + if (slot->snode) { + dedup = cal_dedup_ratio_old(slot); + if (dedup && dedup >= uksm_abundant_threshold) + vma_rung_up(slot); + } + + slot->pages_bemerged = 0; + slot->pages_cowed = 0; + + list_del_init(&slot->dedup_list); + } +} + +static void uksm_del_vma_slot(struct vma_slot *slot) +{ + int i, j; + struct rmap_list_entry *entry; + + if (slot->snode) { + /* + * In case it just failed when entering the rung, it's not + * necessary. + */ + rung_rm_slot(slot); + } + + if (!list_empty(&slot->dedup_list)) + list_del(&slot->dedup_list); + + if (!slot->rmap_list_pool || !slot->pool_counts) { + /* In case it OOMed in uksm_vma_enter() */ + goto out; + } + + for (i = 0; i < slot->pool_size; i++) { + void *addr; + + if (!slot->rmap_list_pool[i]) + continue; + + addr = kmap(slot->rmap_list_pool[i]); + for (j = 0; j < PAGE_SIZE / sizeof(*entry); j++) { + entry = (struct rmap_list_entry *)addr + j; + if (is_addr(entry->addr)) + continue; + if (!entry->item) + continue; + + remove_rmap_item_from_tree(entry->item); + free_rmap_item(entry->item); + slot->pool_counts[i]--; + } + BUG_ON(slot->pool_counts[i]); + kunmap(slot->rmap_list_pool[i]); + __free_page(slot->rmap_list_pool[i]); + } + kfree(slot->rmap_list_pool); + kfree(slot->pool_counts); + +out: + slot->rung = NULL; + if (slot->flags & UKSM_SLOT_IN_UKSM) { + BUG_ON(uksm_pages_total < slot->pages); + uksm_pages_total -= slot->pages; + } + + if (slot->fully_scanned_round == fully_scanned_round) + scanned_virtual_pages -= slot->pages; + else + scanned_virtual_pages -= slot->pages_scanned; + free_vma_slot(slot); +} + + +#define SPIN_LOCK_PERIOD 32 +static struct vma_slot *cleanup_slots[SPIN_LOCK_PERIOD]; +static inline void cleanup_vma_slots(void) +{ + struct vma_slot *slot; + int i; + + i = 0; + spin_lock(&vma_slot_list_lock); + while (!list_empty(&vma_slot_del)) { + slot = list_entry(vma_slot_del.next, + struct vma_slot, slot_list); + list_del(&slot->slot_list); + cleanup_slots[i++] = slot; + if (i == SPIN_LOCK_PERIOD) { + spin_unlock(&vma_slot_list_lock); + while (--i >= 0) + uksm_del_vma_slot(cleanup_slots[i]); + i = 0; + spin_lock(&vma_slot_list_lock); + } + } + spin_unlock(&vma_slot_list_lock); + + while (--i >= 0) + uksm_del_vma_slot(cleanup_slots[i]); +} + +/* + * Expotional moving average formula + */ +static inline unsigned long ema(unsigned long curr, unsigned long last_ema) +{ + /* + * For a very high burst, even the ema cannot work well, a false very + * high per-page time estimation can result in feedback in very high + * overhead of context switch and rung update -- this will then lead + * to higher per-paper time, this may not converge. + * + * Instead, we try to approach this value in a binary manner. + */ + if (curr > last_ema * 10) + return last_ema * 2; + + return (EMA_ALPHA * curr + (100 - EMA_ALPHA) * last_ema) / 100; +} + +/* + * convert cpu ratio in 1/TIME_RATIO_SCALE configured by user to + * nanoseconds based on current uksm_sleep_jiffies. + */ +static inline unsigned long cpu_ratio_to_nsec(unsigned int ratio) +{ + return NSEC_PER_USEC * jiffies_to_usecs(uksm_sleep_jiffies) / + (TIME_RATIO_SCALE - ratio) * ratio; +} + + +static inline unsigned long rung_real_ratio(int cpu_time_ratio) +{ + unsigned long ret; + + BUG_ON(!cpu_time_ratio); + + if (cpu_time_ratio > 0) + ret = cpu_time_ratio; + else + ret = (unsigned long)(-cpu_time_ratio) * + uksm_max_cpu_percentage / 100UL; + + return ret ? ret : 1; +} + +static noinline void uksm_calc_scan_pages(void) +{ + struct scan_rung *ladder = uksm_scan_ladder; + unsigned long sleep_usecs, nsecs; + unsigned long ratio; + int i; + unsigned long per_page; + + if (uksm_ema_page_time > 100000 || + (((unsigned long) uksm_eval_round & (256UL - 1)) == 0UL)) + uksm_ema_page_time = UKSM_PAGE_TIME_DEFAULT; + + per_page = uksm_ema_page_time; + BUG_ON(!per_page); + + /* + * For every 8 eval round, we try to probe a uksm_sleep_jiffies value + * based on saved user input. + */ + if (((unsigned long) uksm_eval_round & (8UL - 1)) == 0UL) + uksm_sleep_jiffies = uksm_sleep_saved; + + /* We require a rung scan at least 1 page in a period. */ + nsecs = per_page; + ratio = rung_real_ratio(ladder[0].cpu_ratio); + if (cpu_ratio_to_nsec(ratio) < nsecs) { + sleep_usecs = nsecs * (TIME_RATIO_SCALE - ratio) / ratio + / NSEC_PER_USEC; + uksm_sleep_jiffies = usecs_to_jiffies(sleep_usecs) + 1; + } + + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + ratio = rung_real_ratio(ladder[i].cpu_ratio); + ladder[i].pages_to_scan = cpu_ratio_to_nsec(ratio) / + per_page; + BUG_ON(!ladder[i].pages_to_scan); + uksm_calc_rung_step(&ladder[i], per_page, ratio); + } +} + +/* + * From the scan time of this round (ns) to next expected min sleep time + * (ms), be careful of the possible overflows. ratio is taken from + * rung_real_ratio() + */ +static inline +unsigned int scan_time_to_sleep(unsigned long long scan_time, unsigned long ratio) +{ + scan_time >>= 20; /* to msec level now */ + BUG_ON(scan_time > (ULONG_MAX / TIME_RATIO_SCALE)); + + return (unsigned int) ((unsigned long) scan_time * + (TIME_RATIO_SCALE - ratio) / ratio); +} + +#define __round_mask(x, y) ((__typeof__(x))((y)-1)) +#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1) + +static void uksm_vma_enter(struct vma_slot **slots, unsigned long num) +{ + struct scan_rung *rung; + + rung = &uksm_scan_ladder[0]; + rung_add_new_slots(rung, slots, num); +} + +static struct vma_slot *batch_slots[SLOT_TREE_NODE_STORE_SIZE]; + +static void uksm_enter_all_slots(void) +{ + struct vma_slot *slot; + unsigned long index; + struct list_head empty_vma_list; + int i; + + i = 0; + index = 0; + INIT_LIST_HEAD(&empty_vma_list); + + spin_lock(&vma_slot_list_lock); + while (!list_empty(&vma_slot_new)) { + slot = list_entry(vma_slot_new.next, + struct vma_slot, slot_list); + + if (!slot->vma->anon_vma) { + list_move(&slot->slot_list, &empty_vma_list); + } else if (vma_can_enter(slot->vma)) { + batch_slots[index++] = slot; + list_del_init(&slot->slot_list); + } else { + list_move(&slot->slot_list, &vma_slot_noadd); + } + + if (++i == SPIN_LOCK_PERIOD || + (index && !(index % SLOT_TREE_NODE_STORE_SIZE))) { + spin_unlock(&vma_slot_list_lock); + + if (index && !(index % SLOT_TREE_NODE_STORE_SIZE)) { + uksm_vma_enter(batch_slots, index); + index = 0; + } + i = 0; + cond_resched(); + spin_lock(&vma_slot_list_lock); + } + } + + list_splice(&empty_vma_list, &vma_slot_new); + + spin_unlock(&vma_slot_list_lock); + + if (index) + uksm_vma_enter(batch_slots, index); + +} + +static inline int rung_round_finished(struct scan_rung *rung) +{ + return rung->flags & UKSM_RUNG_ROUND_FINISHED; +} + +static inline void judge_slot(struct vma_slot *slot) +{ + struct scan_rung *rung = slot->rung; + unsigned long dedup; + int deleted; + + dedup = cal_dedup_ratio(slot); + if (vma_fully_scanned(slot) && uksm_thrash_threshold) + deleted = vma_rung_enter(slot, &uksm_scan_ladder[0]); + else if (dedup && dedup >= uksm_abundant_threshold) + deleted = vma_rung_up(slot); + else + deleted = vma_rung_down(slot); + + slot->pages_merged = 0; + slot->pages_cowed = 0; + slot->this_sampled = 0; + + if (vma_fully_scanned(slot)) + slot->pages_scanned = 0; + + slot->last_scanned = slot->pages_scanned; + + /* If its deleted in above, then rung was already advanced. */ + if (!deleted) + advance_current_scan(rung); +} + + +static inline int hash_round_finished(void) +{ + if (scanned_virtual_pages > (uksm_pages_total >> 2)) { + scanned_virtual_pages = 0; + if (uksm_pages_scanned) + fully_scanned_round++; + + return 1; + } else { + return 0; + } +} + +#define UKSM_MMSEM_BATCH 5 +#define BUSY_RETRY 100 + +/** + * uksm_do_scan() - the main worker function. + */ +static noinline void uksm_do_scan(void) +{ + struct vma_slot *slot, *iter; + struct mm_struct *busy_mm; + unsigned char round_finished, all_rungs_emtpy; + int i, err, mmsem_batch; + unsigned long pcost; + long long delta_exec; + unsigned long vpages, max_cpu_ratio; + unsigned long long start_time, end_time, scan_time; + unsigned int expected_jiffies; + + might_sleep(); + + vpages = 0; + + start_time = task_sched_runtime(current); + max_cpu_ratio = 0; + mmsem_batch = 0; + + for (i = 0; i < SCAN_LADDER_SIZE;) { + struct scan_rung *rung = &uksm_scan_ladder[i]; + unsigned long ratio; + int busy_retry; + + if (!rung->pages_to_scan) { + i++; + continue; + } + + if (!rung->vma_root.num) { + rung->pages_to_scan = 0; + i++; + continue; + } + + ratio = rung_real_ratio(rung->cpu_ratio); + if (ratio > max_cpu_ratio) + max_cpu_ratio = ratio; + + busy_retry = BUSY_RETRY; + /* + * Do not consider rung_round_finished() here, just used up the + * rung->pages_to_scan quota. + */ + while (rung->pages_to_scan && rung->vma_root.num && + likely(!freezing(current))) { + int reset = 0; + + slot = rung->current_scan; + + BUG_ON(vma_fully_scanned(slot)); + + if (mmsem_batch) + err = 0; + else + err = try_down_read_slot_mmap_sem(slot); + + if (err == -ENOENT) { +rm_slot: + rung_rm_slot(slot); + continue; + } + + busy_mm = slot->mm; + + if (err == -EBUSY) { + /* skip other vmas on the same mm */ + do { + reset = advance_current_scan(rung); + iter = rung->current_scan; + busy_retry--; + if (iter->vma->vm_mm != busy_mm || + !busy_retry || reset) + break; + } while (1); + + if (iter->vma->vm_mm != busy_mm) { + continue; + } else { + /* scan round finsished */ + break; + } + } + + BUG_ON(!vma_can_enter(slot->vma)); + if (uksm_test_exit(slot->vma->vm_mm)) { + mmsem_batch = 0; + up_read(&slot->vma->vm_mm->mmap_sem); + goto rm_slot; + } + + if (mmsem_batch) + mmsem_batch--; + else + mmsem_batch = UKSM_MMSEM_BATCH; + + /* Ok, we have take the mmap_sem, ready to scan */ + scan_vma_one_page(slot); + rung->pages_to_scan--; + vpages++; + + if (rung->current_offset + rung->step > slot->pages - 1 + || vma_fully_scanned(slot)) { + up_read(&slot->vma->vm_mm->mmap_sem); + judge_slot(slot); + mmsem_batch = 0; + } else { + rung->current_offset += rung->step; + if (!mmsem_batch) + up_read(&slot->vma->vm_mm->mmap_sem); + } + + busy_retry = BUSY_RETRY; + cond_resched(); + } + + if (mmsem_batch) { + up_read(&slot->vma->vm_mm->mmap_sem); + mmsem_batch = 0; + } + + if (freezing(current)) + break; + + cond_resched(); + } + end_time = task_sched_runtime(current); + delta_exec = end_time - start_time; + + if (freezing(current)) + return; + + cleanup_vma_slots(); + uksm_enter_all_slots(); + + round_finished = 1; + all_rungs_emtpy = 1; + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + struct scan_rung *rung = &uksm_scan_ladder[i]; + + if (rung->vma_root.num) { + all_rungs_emtpy = 0; + if (!rung_round_finished(rung)) + round_finished = 0; + } + } + + if (all_rungs_emtpy) + round_finished = 0; + + if (round_finished) { + round_update_ladder(); + uksm_eval_round++; + + if (hash_round_finished() && rshash_adjust()) { + /* Reset the unstable root iff hash strength changed */ + uksm_hash_round++; + root_unstable_tree = RB_ROOT; + free_all_tree_nodes(&unstable_tree_node_list); + } + + /* + * A number of pages can hang around indefinitely on per-cpu + * pagevecs, raised page count preventing write_protect_page + * from merging them. Though it doesn't really matter much, + * it is puzzling to see some stuck in pages_volatile until + * other activity jostles them out, and they also prevented + * LTP's KSM test from succeeding deterministically; so drain + * them here (here rather than on entry to uksm_do_scan(), + * so we don't IPI too often when pages_to_scan is set low). + */ + lru_add_drain_all(); + } + + + if (vpages && delta_exec > 0) { + pcost = (unsigned long) delta_exec / vpages; + if (likely(uksm_ema_page_time)) + uksm_ema_page_time = ema(pcost, uksm_ema_page_time); + else + uksm_ema_page_time = pcost; + } + + uksm_calc_scan_pages(); + uksm_sleep_real = uksm_sleep_jiffies; + /* in case of radical cpu bursts, apply the upper bound */ + end_time = task_sched_runtime(current); + if (max_cpu_ratio && end_time > start_time) { + scan_time = end_time - start_time; + expected_jiffies = msecs_to_jiffies( + scan_time_to_sleep(scan_time, max_cpu_ratio)); + + if (expected_jiffies > uksm_sleep_real) + uksm_sleep_real = expected_jiffies; + + /* We have a 1 second up bound for responsiveness. */ + if (jiffies_to_msecs(uksm_sleep_real) > MSEC_PER_SEC) + uksm_sleep_real = msecs_to_jiffies(1000); + } + + return; +} + +static int ksmd_should_run(void) +{ + return uksm_run & UKSM_RUN_MERGE; +} + +static int uksm_scan_thread(void *nothing) +{ + set_freezable(); + set_user_nice(current, 5); + + while (!kthread_should_stop()) { + mutex_lock(&uksm_thread_mutex); + if (ksmd_should_run()) + uksm_do_scan(); + mutex_unlock(&uksm_thread_mutex); + + try_to_freeze(); + + if (ksmd_should_run()) { + schedule_timeout_interruptible(uksm_sleep_real); + uksm_sleep_times++; + } else { + wait_event_freezable(uksm_thread_wait, + ksmd_should_run() || kthread_should_stop()); + } + } + return 0; +} + +void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc) +{ + struct stable_node *stable_node; + struct node_vma *node_vma; + struct rmap_item *rmap_item; + int search_new_forks = 0; + unsigned long address; + + VM_BUG_ON_PAGE(!PageKsm(page), page); + VM_BUG_ON_PAGE(!PageLocked(page), page); + + stable_node = page_stable_node(page); + if (!stable_node) + return; +again: + hlist_for_each_entry(node_vma, &stable_node->hlist, hlist) { + hlist_for_each_entry(rmap_item, &node_vma->rmap_hlist, hlist) { + struct anon_vma *anon_vma = rmap_item->anon_vma; + struct anon_vma_chain *vmac; + struct vm_area_struct *vma; + + cond_resched(); + anon_vma_lock_read(anon_vma); + anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, + 0, ULONG_MAX) { + cond_resched(); + vma = vmac->vma; + address = get_rmap_addr(rmap_item); + + if (address < vma->vm_start || + address >= vma->vm_end) + continue; + + if ((rmap_item->slot->vma == vma) == + search_new_forks) + continue; + + if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) + continue; + + if (!rwc->rmap_one(page, vma, address, rwc->arg)) { + anon_vma_unlock_read(anon_vma); + return; + } + + if (rwc->done && rwc->done(page)) { + anon_vma_unlock_read(anon_vma); + return; + } + } + anon_vma_unlock_read(anon_vma); + } + } + if (!search_new_forks++) + goto again; +} + +#ifdef CONFIG_MIGRATION +/* Common ksm interface but may be specific to uksm */ +void ksm_migrate_page(struct page *newpage, struct page *oldpage) +{ + struct stable_node *stable_node; + + VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage); + VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); + VM_BUG_ON(newpage->mapping != oldpage->mapping); + + stable_node = page_stable_node(newpage); + if (stable_node) { + VM_BUG_ON(stable_node->kpfn != page_to_pfn(oldpage)); + stable_node->kpfn = page_to_pfn(newpage); + /* + * newpage->mapping was set in advance; now we need smp_wmb() + * to make sure that the new stable_node->kpfn is visible + * to get_ksm_page() before it can see that oldpage->mapping + * has gone stale (or that PageSwapCache has been cleared). + */ + smp_wmb(); + set_page_stable_node(oldpage, NULL); + } +} +#endif /* CONFIG_MIGRATION */ + +#ifdef CONFIG_MEMORY_HOTREMOVE +static struct stable_node *uksm_check_stable_tree(unsigned long start_pfn, + unsigned long end_pfn) +{ + struct rb_node *node; + + for (node = rb_first(root_stable_treep); node; node = rb_next(node)) { + struct stable_node *stable_node; + + stable_node = rb_entry(node, struct stable_node, node); + if (stable_node->kpfn >= start_pfn && + stable_node->kpfn < end_pfn) + return stable_node; + } + return NULL; +} + +static int uksm_memory_callback(struct notifier_block *self, + unsigned long action, void *arg) +{ + struct memory_notify *mn = arg; + struct stable_node *stable_node; + + switch (action) { + case MEM_GOING_OFFLINE: + /* + * Keep it very simple for now: just lock out ksmd and + * MADV_UNMERGEABLE while any memory is going offline. + * mutex_lock_nested() is necessary because lockdep was alarmed + * that here we take uksm_thread_mutex inside notifier chain + * mutex, and later take notifier chain mutex inside + * uksm_thread_mutex to unlock it. But that's safe because both + * are inside mem_hotplug_mutex. + */ + mutex_lock_nested(&uksm_thread_mutex, SINGLE_DEPTH_NESTING); + break; + + case MEM_OFFLINE: + /* + * Most of the work is done by page migration; but there might + * be a few stable_nodes left over, still pointing to struct + * pages which have been offlined: prune those from the tree. + */ + while ((stable_node = uksm_check_stable_tree(mn->start_pfn, + mn->start_pfn + mn->nr_pages)) != NULL) + remove_node_from_stable_tree(stable_node, 1, 1); + /* fallthrough */ + + case MEM_CANCEL_OFFLINE: + mutex_unlock(&uksm_thread_mutex); + break; + } + return NOTIFY_OK; +} +#endif /* CONFIG_MEMORY_HOTREMOVE */ + +#ifdef CONFIG_SYSFS +/* + * This all compiles without CONFIG_SYSFS, but is a waste of space. + */ + +#define UKSM_ATTR_RO(_name) \ + static struct kobj_attribute _name##_attr = __ATTR_RO(_name) +#define UKSM_ATTR(_name) \ + static struct kobj_attribute _name##_attr = \ + __ATTR(_name, 0644, _name##_show, _name##_store) + +static ssize_t max_cpu_percentage_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%u\n", uksm_max_cpu_percentage); +} + +static ssize_t max_cpu_percentage_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned long max_cpu_percentage; + int err; + + err = kstrtoul(buf, 10, &max_cpu_percentage); + if (err || max_cpu_percentage > 100) + return -EINVAL; + + if (max_cpu_percentage == 100) + max_cpu_percentage = 99; + else if (max_cpu_percentage < 10) + max_cpu_percentage = 10; + + uksm_max_cpu_percentage = max_cpu_percentage; + + return count; +} +UKSM_ATTR(max_cpu_percentage); + +static ssize_t sleep_millisecs_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%u\n", jiffies_to_msecs(uksm_sleep_jiffies)); +} + +static ssize_t sleep_millisecs_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned long msecs; + int err; + + err = kstrtoul(buf, 10, &msecs); + if (err || msecs > MSEC_PER_SEC) + return -EINVAL; + + uksm_sleep_jiffies = msecs_to_jiffies(msecs); + uksm_sleep_saved = uksm_sleep_jiffies; + + return count; +} +UKSM_ATTR(sleep_millisecs); + + +static ssize_t cpu_governor_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + int n = sizeof(uksm_cpu_governor_str) / sizeof(char *); + int i; + + buf[0] = '\0'; + for (i = 0; i < n ; i++) { + if (uksm_cpu_governor == i) + strcat(buf, "["); + + strcat(buf, uksm_cpu_governor_str[i]); + + if (uksm_cpu_governor == i) + strcat(buf, "]"); + + strcat(buf, " "); + } + strcat(buf, "\n"); + + return strlen(buf); +} + +static inline void init_performance_values(void) +{ + int i; + struct scan_rung *rung; + struct uksm_cpu_preset_s *preset = uksm_cpu_preset + uksm_cpu_governor; + + + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + rung = uksm_scan_ladder + i; + rung->cpu_ratio = preset->cpu_ratio[i]; + rung->cover_msecs = preset->cover_msecs[i]; + } + + uksm_max_cpu_percentage = preset->max_cpu; +} + +static ssize_t cpu_governor_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int n = sizeof(uksm_cpu_governor_str) / sizeof(char *); + + for (n--; n >= 0 ; n--) { + if (!strncmp(buf, uksm_cpu_governor_str[n], + strlen(uksm_cpu_governor_str[n]))) + break; + } + + if (n < 0) + return -EINVAL; + else + uksm_cpu_governor = n; + + init_performance_values(); + + return count; +} +UKSM_ATTR(cpu_governor); + +static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", uksm_run); +} + +static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long flags; + + err = kstrtoul(buf, 10, &flags); + if (err || flags > UINT_MAX) + return -EINVAL; + if (flags > UKSM_RUN_MERGE) + return -EINVAL; + + mutex_lock(&uksm_thread_mutex); + if (uksm_run != flags) + uksm_run = flags; + mutex_unlock(&uksm_thread_mutex); + + if (flags & UKSM_RUN_MERGE) + wake_up_interruptible(&uksm_thread_wait); + + return count; +} +UKSM_ATTR(run); + +static ssize_t abundant_threshold_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%u\n", uksm_abundant_threshold); +} + +static ssize_t abundant_threshold_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long flags; + + err = kstrtoul(buf, 10, &flags); + if (err || flags > 99) + return -EINVAL; + + uksm_abundant_threshold = flags; + + return count; +} +UKSM_ATTR(abundant_threshold); + +static ssize_t thrash_threshold_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%u\n", uksm_thrash_threshold); +} + +static ssize_t thrash_threshold_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long flags; + + err = kstrtoul(buf, 10, &flags); + if (err || flags > 99) + return -EINVAL; + + uksm_thrash_threshold = flags; + + return count; +} +UKSM_ATTR(thrash_threshold); + +static ssize_t cpu_ratios_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + int i, size; + struct scan_rung *rung; + char *p = buf; + + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + rung = &uksm_scan_ladder[i]; + + if (rung->cpu_ratio > 0) + size = sprintf(p, "%d ", rung->cpu_ratio); + else + size = sprintf(p, "MAX/%d ", + TIME_RATIO_SCALE / -rung->cpu_ratio); + + p += size; + } + + *p++ = '\n'; + *p = '\0'; + + return p - buf; +} + +static ssize_t cpu_ratios_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int i, cpuratios[SCAN_LADDER_SIZE], err; + unsigned long value; + struct scan_rung *rung; + char *p, *end = NULL; + + p = kzalloc(count, GFP_KERNEL); + if (!p) + return -ENOMEM; + + memcpy(p, buf, count); + + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + if (i != SCAN_LADDER_SIZE - 1) { + end = strchr(p, ' '); + if (!end) + return -EINVAL; + + *end = '\0'; + } + + if (strstr(p, "MAX/")) { + p = strchr(p, '/') + 1; + err = kstrtoul(p, 10, &value); + if (err || value > TIME_RATIO_SCALE || !value) + return -EINVAL; + + cpuratios[i] = -(int) (TIME_RATIO_SCALE / value); + } else { + err = kstrtoul(p, 10, &value); + if (err || value > TIME_RATIO_SCALE || !value) + return -EINVAL; + + cpuratios[i] = value; + } + + p = end + 1; + } + + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + rung = &uksm_scan_ladder[i]; + + rung->cpu_ratio = cpuratios[i]; + } + + return count; +} +UKSM_ATTR(cpu_ratios); + +static ssize_t eval_intervals_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + int i, size; + struct scan_rung *rung; + char *p = buf; + + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + rung = &uksm_scan_ladder[i]; + size = sprintf(p, "%u ", rung->cover_msecs); + p += size; + } + + *p++ = '\n'; + *p = '\0'; + + return p - buf; +} + +static ssize_t eval_intervals_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int i, err; + unsigned long values[SCAN_LADDER_SIZE]; + struct scan_rung *rung; + char *p, *end = NULL; + ssize_t ret = count; + + p = kzalloc(count + 2, GFP_KERNEL); + if (!p) + return -ENOMEM; + + memcpy(p, buf, count); + + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + if (i != SCAN_LADDER_SIZE - 1) { + end = strchr(p, ' '); + if (!end) { + ret = -EINVAL; + goto out; + } + + *end = '\0'; + } + + err = kstrtoul(p, 10, &values[i]); + if (err) { + ret = -EINVAL; + goto out; + } + + p = end + 1; + } + + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + rung = &uksm_scan_ladder[i]; + + rung->cover_msecs = values[i]; + } + +out: + kfree(p); + return ret; +} +UKSM_ATTR(eval_intervals); + +static ssize_t ema_per_page_time_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", uksm_ema_page_time); +} +UKSM_ATTR_RO(ema_per_page_time); + +static ssize_t pages_shared_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", uksm_pages_shared); +} +UKSM_ATTR_RO(pages_shared); + +static ssize_t pages_sharing_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", uksm_pages_sharing); +} +UKSM_ATTR_RO(pages_sharing); + +static ssize_t pages_unshared_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", uksm_pages_unshared); +} +UKSM_ATTR_RO(pages_unshared); + +static ssize_t full_scans_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%llu\n", fully_scanned_round); +} +UKSM_ATTR_RO(full_scans); + +static ssize_t pages_scanned_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + unsigned long base = 0; + u64 delta, ret; + + if (pages_scanned_stored) { + base = pages_scanned_base; + ret = pages_scanned_stored; + delta = uksm_pages_scanned >> base; + if (CAN_OVERFLOW_U64(ret, delta)) { + ret >>= 1; + delta >>= 1; + base++; + ret += delta; + } + } else { + ret = uksm_pages_scanned; + } + + while (ret > ULONG_MAX) { + ret >>= 1; + base++; + } + + if (base) + return sprintf(buf, "%lu * 2^%lu\n", (unsigned long)ret, base); + else + return sprintf(buf, "%lu\n", (unsigned long)ret); +} +UKSM_ATTR_RO(pages_scanned); + +static ssize_t hash_strength_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", hash_strength); +} +UKSM_ATTR_RO(hash_strength); + +static ssize_t sleep_times_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%llu\n", uksm_sleep_times); +} +UKSM_ATTR_RO(sleep_times); + + +static struct attribute *uksm_attrs[] = { + &max_cpu_percentage_attr.attr, + &sleep_millisecs_attr.attr, + &cpu_governor_attr.attr, + &run_attr.attr, + &ema_per_page_time_attr.attr, + &pages_shared_attr.attr, + &pages_sharing_attr.attr, + &pages_unshared_attr.attr, + &full_scans_attr.attr, + &pages_scanned_attr.attr, + &hash_strength_attr.attr, + &sleep_times_attr.attr, + &thrash_threshold_attr.attr, + &abundant_threshold_attr.attr, + &cpu_ratios_attr.attr, + &eval_intervals_attr.attr, + NULL, +}; + +static struct attribute_group uksm_attr_group = { + .attrs = uksm_attrs, + .name = "uksm", +}; +#endif /* CONFIG_SYSFS */ + +static inline void init_scan_ladder(void) +{ + int i; + struct scan_rung *rung; + + for (i = 0; i < SCAN_LADDER_SIZE; i++) { + rung = uksm_scan_ladder + i; + slot_tree_init_root(&rung->vma_root); + } + + init_performance_values(); + uksm_calc_scan_pages(); +} + +static inline int cal_positive_negative_costs(void) +{ + struct page *p1, *p2; + unsigned char *addr1, *addr2; + unsigned long i, time_start, hash_cost; + unsigned long loopnum = 0; + + /*IMPORTANT: volatile is needed to prevent over-optimization by gcc. */ + volatile u32 hash; + volatile int ret; + + p1 = alloc_page(GFP_KERNEL); + if (!p1) + return -ENOMEM; + + p2 = alloc_page(GFP_KERNEL); + if (!p2) + return -ENOMEM; + + addr1 = kmap_atomic(p1); + addr2 = kmap_atomic(p2); + memset(addr1, prandom_u32(), PAGE_SIZE); + memcpy(addr2, addr1, PAGE_SIZE); + + /* make sure that the two pages differ in last byte */ + addr2[PAGE_SIZE-1] = ~addr2[PAGE_SIZE-1]; + kunmap_atomic(addr2); + kunmap_atomic(addr1); + + time_start = jiffies; + while (jiffies - time_start < 100) { + for (i = 0; i < 100; i++) + hash = page_hash(p1, HASH_STRENGTH_FULL, 0); + loopnum += 100; + } + hash_cost = (jiffies - time_start); + + time_start = jiffies; + for (i = 0; i < loopnum; i++) + ret = pages_identical(p1, p2); + memcmp_cost = HASH_STRENGTH_FULL * (jiffies - time_start); + memcmp_cost /= hash_cost; + pr_info("UKSM: relative memcmp_cost = %lu " + "hash=%u cmp_ret=%d.\n", + memcmp_cost, hash, ret); + + __free_page(p1); + __free_page(p2); + return 0; +} + +static int init_zeropage_hash_table(void) +{ + struct page *page; + char *addr; + int i; + + page = alloc_page(GFP_KERNEL); + if (!page) + return -ENOMEM; + + addr = kmap_atomic(page); + memset(addr, 0, PAGE_SIZE); + kunmap_atomic(addr); + + zero_hash_table = kmalloc_array(HASH_STRENGTH_MAX, sizeof(u32), + GFP_KERNEL); + if (!zero_hash_table) + return -ENOMEM; + + for (i = 0; i < HASH_STRENGTH_MAX; i++) + zero_hash_table[i] = page_hash(page, i, 0); + + __free_page(page); + + return 0; +} + +static inline int init_random_sampling(void) +{ + unsigned long i; + + random_nums = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!random_nums) + return -ENOMEM; + + for (i = 0; i < HASH_STRENGTH_FULL; i++) + random_nums[i] = i; + + for (i = 0; i < HASH_STRENGTH_FULL; i++) { + unsigned long rand_range, swap_index, tmp; + + rand_range = HASH_STRENGTH_FULL - i; + swap_index = i + prandom_u32() % rand_range; + tmp = random_nums[i]; + random_nums[i] = random_nums[swap_index]; + random_nums[swap_index] = tmp; + } + + rshash_state.state = RSHASH_NEW; + rshash_state.below_count = 0; + rshash_state.lookup_window_index = 0; + + return cal_positive_negative_costs(); +} + +static int __init uksm_slab_init(void) +{ + rmap_item_cache = UKSM_KMEM_CACHE(rmap_item, 0); + if (!rmap_item_cache) + goto out; + + stable_node_cache = UKSM_KMEM_CACHE(stable_node, 0); + if (!stable_node_cache) + goto out_free1; + + node_vma_cache = UKSM_KMEM_CACHE(node_vma, 0); + if (!node_vma_cache) + goto out_free2; + + vma_slot_cache = UKSM_KMEM_CACHE(vma_slot, 0); + if (!vma_slot_cache) + goto out_free3; + + tree_node_cache = UKSM_KMEM_CACHE(tree_node, 0); + if (!tree_node_cache) + goto out_free4; + + return 0; + +out_free4: + kmem_cache_destroy(vma_slot_cache); +out_free3: + kmem_cache_destroy(node_vma_cache); +out_free2: + kmem_cache_destroy(stable_node_cache); +out_free1: + kmem_cache_destroy(rmap_item_cache); +out: + return -ENOMEM; +} + +static void __init uksm_slab_free(void) +{ + kmem_cache_destroy(stable_node_cache); + kmem_cache_destroy(rmap_item_cache); + kmem_cache_destroy(node_vma_cache); + kmem_cache_destroy(vma_slot_cache); + kmem_cache_destroy(tree_node_cache); +} + +/* Common interface to ksm, different to it. */ +int ksm_madvise(struct vm_area_struct *vma, unsigned long start, + unsigned long end, int advice, unsigned long *vm_flags) +{ + int err; + + switch (advice) { + case MADV_MERGEABLE: + return 0; /* just ignore the advice */ + + case MADV_UNMERGEABLE: + if (!(*vm_flags & VM_MERGEABLE) || !uksm_flags_can_scan(*vm_flags)) + return 0; /* just ignore the advice */ + + if (vma->anon_vma) { + err = unmerge_uksm_pages(vma, start, end); + if (err) + return err; + } + + uksm_remove_vma(vma); + *vm_flags &= ~VM_MERGEABLE; + break; + } + + return 0; +} + +/* Common interface to ksm, actually the same. */ +struct page *ksm_might_need_to_copy(struct page *page, + struct vm_area_struct *vma, unsigned long address) +{ + struct anon_vma *anon_vma = page_anon_vma(page); + struct page *new_page; + + if (PageKsm(page)) { + if (page_stable_node(page)) + return page; /* no need to copy it */ + } else if (!anon_vma) { + return page; /* no need to copy it */ + } else if (anon_vma->root == vma->anon_vma->root && + page->index == linear_page_index(vma, address)) { + return page; /* still no need to copy it */ + } + if (!PageUptodate(page)) + return page; /* let do_swap_page report the error */ + + new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); + if (new_page) { + copy_user_highpage(new_page, page, address, vma); + + SetPageDirty(new_page); + __SetPageUptodate(new_page); + __SetPageLocked(new_page); + } + + return new_page; +} + +static int __init uksm_init(void) +{ + struct task_struct *uksm_thread; + int err; + + uksm_sleep_jiffies = msecs_to_jiffies(100); + uksm_sleep_saved = uksm_sleep_jiffies; + + slot_tree_init(); + init_scan_ladder(); + + + err = init_random_sampling(); + if (err) + goto out_free2; + + err = uksm_slab_init(); + if (err) + goto out_free1; + + err = init_zeropage_hash_table(); + if (err) + goto out_free0; + + uksm_thread = kthread_run(uksm_scan_thread, NULL, "uksmd"); + if (IS_ERR(uksm_thread)) { + pr_err("uksm: creating kthread failed\n"); + err = PTR_ERR(uksm_thread); + goto out_free; + } + +#ifdef CONFIG_SYSFS + err = sysfs_create_group(mm_kobj, &uksm_attr_group); + if (err) { + pr_err("uksm: register sysfs failed\n"); + kthread_stop(uksm_thread); + goto out_free; + } +#else + uksm_run = UKSM_RUN_MERGE; /* no way for user to start it */ + +#endif /* CONFIG_SYSFS */ + +#ifdef CONFIG_MEMORY_HOTREMOVE + /* + * Choose a high priority since the callback takes uksm_thread_mutex: + * later callbacks could only be taking locks which nest within that. + */ + hotplug_memory_notifier(uksm_memory_callback, 100); +#endif + return 0; + +out_free: + kfree(zero_hash_table); +out_free0: + uksm_slab_free(); +out_free1: + kfree(random_nums); +out_free2: + kfree(uksm_scan_ladder); + return err; +} + +#ifdef MODULE +subsys_initcall(ksm_init); +#else +late_initcall(uksm_init); +#endif + diff --git a/mm/vmstat.c b/mm/vmstat.c index 33581be70..f2eb7b480 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1162,6 +1162,9 @@ const char * const vmstat_text[] = { "nr_dirtied", "nr_written", +#ifdef CONFIG_UKSM + "nr_uksm_zero_pages", +#endif /* enum writeback_stat_item counters */ "nr_dirty_threshold", "nr_dirty_background_threshold",