diff options
| -rw-r--r-- | mm/ksm.c | 180 |
1 files changed, 101 insertions, 79 deletions
@@ -106,34 +106,44 @@ struct ksm_scan { }; /** + * 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 + */ +struct stable_node { + struct rb_node node; + struct hlist_head hlist; +}; + +/** * struct rmap_item - reverse mapping item for virtual addresses * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list * @filler: unused space we're making available in this patch * @mm: the memory structure this rmap_item is pointing into * @address: the virtual address this rmap_item tracks (+ flags in low bits) * @oldchecksum: previous checksum of the page at that virtual address - * @node: rb_node of this rmap_item in either unstable or stable tree - * @next: next rmap_item hanging off the same node of the stable tree - * @prev: previous rmap_item hanging off the same node of the stable tree + * @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 rmap_item *rmap_list; unsigned long filler; struct mm_struct *mm; unsigned long address; /* + low bits used for flags below */ + unsigned int oldchecksum; /* when unstable */ union { - unsigned int oldchecksum; /* when unstable */ - struct rmap_item *next; /* when stable */ - }; - union { - struct rb_node node; /* when tree node */ - struct rmap_item *prev; /* in stable list */ + struct rb_node node; /* when node of unstable tree */ + struct { /* when listed from stable tree */ + struct stable_node *head; + struct hlist_node hlist; + }; }; }; #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ -#define NODE_FLAG 0x100 /* is a node of unstable or stable tree */ -#define STABLE_FLAG 0x200 /* is a node or list item of stable tree */ +#define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ +#define STABLE_FLAG 0x200 /* is listed from the stable tree */ /* The stable and unstable tree heads */ static struct rb_root root_stable_tree = RB_ROOT; @@ -150,6 +160,7 @@ static struct ksm_scan ksm_scan = { }; static struct kmem_cache *rmap_item_cache; +static struct kmem_cache *stable_node_cache; static struct kmem_cache *mm_slot_cache; /* The number of nodes in the stable tree */ @@ -192,13 +203,19 @@ static int __init ksm_slab_init(void) if (!rmap_item_cache) goto out; + stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); + if (!stable_node_cache) + goto out_free1; + mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); if (!mm_slot_cache) - goto out_free; + goto out_free2; return 0; -out_free: +out_free2: + kmem_cache_destroy(stable_node_cache); +out_free1: kmem_cache_destroy(rmap_item_cache); out: return -ENOMEM; @@ -207,6 +224,7 @@ out: static void __init ksm_slab_free(void) { kmem_cache_destroy(mm_slot_cache); + kmem_cache_destroy(stable_node_cache); kmem_cache_destroy(rmap_item_cache); mm_slot_cache = NULL; } @@ -228,6 +246,16 @@ static inline void free_rmap_item(struct rmap_item *rmap_item) kmem_cache_free(rmap_item_cache, rmap_item); } +static inline struct stable_node *alloc_stable_node(void) +{ + return kmem_cache_alloc(stable_node_cache, GFP_KERNEL); +} + +static inline void free_stable_node(struct stable_node *stable_node) +{ + kmem_cache_free(stable_node_cache, stable_node); +} + static inline struct mm_slot *alloc_mm_slot(void) { if (!mm_slot_cache) /* initialization failed */ @@ -429,36 +457,22 @@ static struct page *get_ksm_page(struct rmap_item *rmap_item) */ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) { - if (in_stable_tree(rmap_item)) { - struct rmap_item *next_item = rmap_item->next; - - if (rmap_item->address & NODE_FLAG) { - if (next_item) { - rb_replace_node(&rmap_item->node, - &next_item->node, - &root_stable_tree); - next_item->address |= NODE_FLAG; - ksm_pages_sharing--; - } else { - rb_erase(&rmap_item->node, &root_stable_tree); - ksm_pages_shared--; - } - } else { - struct rmap_item *prev_item = rmap_item->prev; + if (rmap_item->address & STABLE_FLAG) { + struct stable_node *stable_node; - BUG_ON(prev_item->next != rmap_item); - prev_item->next = next_item; - if (next_item) { - BUG_ON(next_item->prev != rmap_item); - next_item->prev = rmap_item->prev; - } + stable_node = rmap_item->head; + hlist_del(&rmap_item->hlist); + if (stable_node->hlist.first) ksm_pages_sharing--; + else { + rb_erase(&stable_node->node, &root_stable_tree); + free_stable_node(stable_node); + ksm_pages_shared--; } - rmap_item->next = NULL; rmap_item->address &= PAGE_MASK; - } else if (rmap_item->address & NODE_FLAG) { + } else if (rmap_item->address & UNSTABLE_FLAG) { unsigned char age; /* * Usually ksmd can and must skip the rb_erase, because @@ -859,31 +873,32 @@ up: * This function checks if there is a page inside the stable tree * with identical content to the page that we are scanning right now. * - * This function return rmap_item pointer to the identical item if found, + * This function returns the stable tree node of identical content if found, * NULL otherwise. */ -static struct rmap_item *stable_tree_search(struct page *page, - struct page **tree_pagep) +static struct stable_node *stable_tree_search(struct page *page, + struct page **tree_pagep) { struct rb_node *node = root_stable_tree.rb_node; + struct stable_node *stable_node; while (node) { - struct rmap_item *tree_rmap_item, *next_rmap_item; + struct hlist_node *hlist, *hnext; + struct rmap_item *tree_rmap_item; struct page *tree_page; int ret; - tree_rmap_item = rb_entry(node, struct rmap_item, node); - while (tree_rmap_item) { + stable_node = rb_entry(node, struct stable_node, node); + hlist_for_each_entry_safe(tree_rmap_item, hlist, hnext, + &stable_node->hlist, hlist) { BUG_ON(!in_stable_tree(tree_rmap_item)); cond_resched(); tree_page = get_ksm_page(tree_rmap_item); if (tree_page) break; - next_rmap_item = tree_rmap_item->next; remove_rmap_item_from_tree(tree_rmap_item); - tree_rmap_item = next_rmap_item; } - if (!tree_rmap_item) + if (!hlist) return NULL; ret = memcmp_pages(page, tree_page); @@ -896,7 +911,7 @@ static struct rmap_item *stable_tree_search(struct page *page, node = node->rb_right; } else { *tree_pagep = tree_page; - return tree_rmap_item; + return stable_node; } } @@ -907,31 +922,32 @@ static struct rmap_item *stable_tree_search(struct page *page, * stable_tree_insert - insert rmap_item pointing to new ksm page * into the stable tree. * - * This function returns rmap_item if success, NULL otherwise. + * This function returns the stable tree node just allocated on success, + * NULL otherwise. */ -static struct rmap_item *stable_tree_insert(struct page *kpage, - struct rmap_item *rmap_item) +static struct stable_node *stable_tree_insert(struct page *kpage) { struct rb_node **new = &root_stable_tree.rb_node; struct rb_node *parent = NULL; + struct stable_node *stable_node; while (*new) { - struct rmap_item *tree_rmap_item, *next_rmap_item; + struct hlist_node *hlist, *hnext; + struct rmap_item *tree_rmap_item; struct page *tree_page; int ret; - tree_rmap_item = rb_entry(*new, struct rmap_item, node); - while (tree_rmap_item) { + stable_node = rb_entry(*new, struct stable_node, node); + hlist_for_each_entry_safe(tree_rmap_item, hlist, hnext, + &stable_node->hlist, hlist) { BUG_ON(!in_stable_tree(tree_rmap_item)); cond_resched(); tree_page = get_ksm_page(tree_rmap_item); if (tree_page) break; - next_rmap_item = tree_rmap_item->next; remove_rmap_item_from_tree(tree_rmap_item); - tree_rmap_item = next_rmap_item; } - if (!tree_rmap_item) + if (!hlist) return NULL; ret = memcmp_pages(kpage, tree_page); @@ -952,13 +968,16 @@ static struct rmap_item *stable_tree_insert(struct page *kpage, } } - rmap_item->address |= NODE_FLAG | STABLE_FLAG; - rmap_item->next = NULL; - rb_link_node(&rmap_item->node, parent, new); - rb_insert_color(&rmap_item->node, &root_stable_tree); + stable_node = alloc_stable_node(); + if (!stable_node) + return NULL; - ksm_pages_shared++; - return rmap_item; + rb_link_node(&stable_node->node, parent, new); + rb_insert_color(&stable_node->node, &root_stable_tree); + + INIT_HLIST_HEAD(&stable_node->hlist); + + return stable_node; } /* @@ -1018,7 +1037,7 @@ struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, } } - rmap_item->address |= NODE_FLAG; + rmap_item->address |= UNSTABLE_FLAG; rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); rb_link_node(&rmap_item->node, parent, new); rb_insert_color(&rmap_item->node, &root_unstable_tree); @@ -1033,18 +1052,16 @@ struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, * the same ksm page. */ static void stable_tree_append(struct rmap_item *rmap_item, - struct rmap_item *tree_rmap_item) + struct stable_node *stable_node) { - rmap_item->next = tree_rmap_item->next; - rmap_item->prev = tree_rmap_item; - - if (tree_rmap_item->next) - tree_rmap_item->next->prev = rmap_item; - - tree_rmap_item->next = rmap_item; + rmap_item->head = stable_node; rmap_item->address |= STABLE_FLAG; + hlist_add_head(&rmap_item->hlist, &stable_node->hlist); - ksm_pages_sharing++; + if (rmap_item->hlist.next) + ksm_pages_sharing++; + else + ksm_pages_shared++; } /* @@ -1060,6 +1077,7 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) { struct rmap_item *tree_rmap_item; struct page *tree_page = NULL; + struct stable_node *stable_node; struct page *kpage; unsigned int checksum; int err; @@ -1067,8 +1085,8 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) remove_rmap_item_from_tree(rmap_item); /* We first start with searching the page inside the stable tree */ - tree_rmap_item = stable_tree_search(page, &tree_page); - if (tree_rmap_item) { + stable_node = stable_tree_search(page, &tree_page); + if (stable_node) { kpage = tree_page; if (page == kpage) /* forked */ err = 0; @@ -1080,7 +1098,7 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) * The page was successfully merged: * add its rmap_item to the stable tree. */ - stable_tree_append(rmap_item, tree_rmap_item); + stable_tree_append(rmap_item, stable_node); } put_page(kpage); return; @@ -1121,19 +1139,23 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) if (kpage) { remove_rmap_item_from_tree(tree_rmap_item); + stable_node = stable_tree_insert(kpage); + if (stable_node) { + stable_tree_append(tree_rmap_item, stable_node); + stable_tree_append(rmap_item, stable_node); + } + put_page(kpage); + /* * If we fail to insert the page into the stable tree, * we will have 2 virtual addresses that are pointing * to a ksm page left outside the stable tree, * in which case we need to break_cow on both. */ - if (stable_tree_insert(kpage, tree_rmap_item)) - stable_tree_append(rmap_item, tree_rmap_item); - else { + if (!stable_node) { break_cow(tree_rmap_item); break_cow(rmap_item); } - put_page(kpage); } } } |