From f728b0a5d72ae99c446f933912914a61254c03b6 Mon Sep 17 00:00:00 2001 From: Greg Thelen Date: Mon, 12 Dec 2016 16:41:41 -0800 Subject: [PATCH] mm, slab: faster active and free stats Reading /proc/slabinfo or monitoring slabtop(1) can become very expensive if there are many slab caches and if there are very lengthy per-node partial and/or free lists. Commit 07a63c41fa1f ("mm/slab: improve performance of gathering slabinfo stats") addressed the per-node full lists which showed a significant improvement when no objects were freed. This patch has the same motivation and optimizes the remainder of the usecases where there are very lengthy partial and free lists. This patch maintains per-node active_slabs (full and partial) and free_slabs rather than iterating the lists at runtime when reading /proc/slabinfo. When allocating 100GB of slab from a test cache where every slab page is on the partial list, reading /proc/slabinfo (includes all other slab caches on the system) takes ~247ms on average with 48 samples. As a result of this patch, the same read takes ~0.856ms on average. [rientjes@google.com: changelog] Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1611081505240.13403@chino.kir.corp.google.com Signed-off-by: Greg Thelen Signed-off-by: David Rientjes Cc: Christoph Lameter Cc: Pekka Enberg Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slab.c | 117 ++++++++++++++++++++++-------------------------------- mm/slab.h | 3 +- 2 files changed, 49 insertions(+), 71 deletions(-) diff --git a/mm/slab.c b/mm/slab.c index 7ea765cd7e93..e06da6ceaf73 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -227,13 +227,14 @@ static void kmem_cache_node_init(struct kmem_cache_node *parent) INIT_LIST_HEAD(&parent->slabs_full); INIT_LIST_HEAD(&parent->slabs_partial); INIT_LIST_HEAD(&parent->slabs_free); + parent->active_slabs = 0; + parent->free_slabs = 0; parent->shared = NULL; parent->alien = NULL; parent->colour_next = 0; spin_lock_init(&parent->list_lock); parent->free_objects = 0; parent->free_touched = 0; - parent->num_slabs = 0; } #define MAKE_LIST(cachep, listp, slab, nodeid) \ @@ -1366,7 +1367,6 @@ slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid) { #if DEBUG struct kmem_cache_node *n; - struct page *page; unsigned long flags; int node; static DEFINE_RATELIMIT_STATE(slab_oom_rs, DEFAULT_RATELIMIT_INTERVAL, @@ -1381,32 +1381,20 @@ slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid) cachep->name, cachep->size, cachep->gfporder); for_each_kmem_cache_node(cachep, node, n) { - unsigned long active_objs = 0, num_objs = 0, free_objects = 0; - unsigned long active_slabs = 0, num_slabs = 0; - unsigned long num_slabs_partial = 0, num_slabs_free = 0; - unsigned long num_slabs_full; + unsigned long active_objs = 0, free_objs = 0; + unsigned long active_slabs, num_slabs; spin_lock_irqsave(&n->list_lock, flags); - num_slabs = n->num_slabs; - list_for_each_entry(page, &n->slabs_partial, lru) { - active_objs += page->active; - num_slabs_partial++; - } - list_for_each_entry(page, &n->slabs_free, lru) - num_slabs_free++; + active_slabs = n->active_slabs; + num_slabs = active_slabs + n->free_slabs; - free_objects += n->free_objects; + active_objs += (num_slabs * cachep->num) - n->free_objects; + free_objs += n->free_objects; spin_unlock_irqrestore(&n->list_lock, flags); - num_objs = num_slabs * cachep->num; - active_slabs = num_slabs - num_slabs_free; - num_slabs_full = num_slabs - - (num_slabs_partial + num_slabs_free); - active_objs += (num_slabs_full * cachep->num); - pr_warn(" node %d: slabs: %ld/%ld, objs: %ld/%ld, free: %ld\n", - node, active_slabs, num_slabs, active_objs, num_objs, - free_objects); + node, active_slabs, num_slabs, active_objs, + num_slabs * cachep->num, free_objs); } #endif } @@ -2318,7 +2306,7 @@ static int drain_freelist(struct kmem_cache *cache, page = list_entry(p, struct page, lru); list_del(&page->lru); - n->num_slabs--; + n->free_slabs--; /* * Safe to drop the lock. The slab is no longer linked * to the cache. @@ -2753,12 +2741,14 @@ static void cache_grow_end(struct kmem_cache *cachep, struct page *page) n = get_node(cachep, page_to_nid(page)); spin_lock(&n->list_lock); - if (!page->active) + if (!page->active) { list_add_tail(&page->lru, &(n->slabs_free)); - else + n->free_slabs++; + } else { fixup_slab_list(cachep, n, page, &list); + n->active_slabs++; + } - n->num_slabs++; STATS_INC_GROWN(cachep); n->free_objects += cachep->num - page->active; spin_unlock(&n->list_lock); @@ -2884,7 +2874,7 @@ static inline void fixup_slab_list(struct kmem_cache *cachep, /* Try to find non-pfmemalloc slab if needed */ static noinline struct page *get_valid_first_slab(struct kmem_cache_node *n, - struct page *page, bool pfmemalloc) + struct page *page, bool *page_is_free, bool pfmemalloc) { if (!page) return NULL; @@ -2903,9 +2893,11 @@ static noinline struct page *get_valid_first_slab(struct kmem_cache_node *n, /* Move pfmemalloc slab to the end of list to speed up next search */ list_del(&page->lru); - if (!page->active) + if (*page_is_free) { + WARN_ON(page->active); list_add_tail(&page->lru, &n->slabs_free); - else + *page_is_free = false; + } else list_add_tail(&page->lru, &n->slabs_partial); list_for_each_entry(page, &n->slabs_partial, lru) { @@ -2913,9 +2905,12 @@ static noinline struct page *get_valid_first_slab(struct kmem_cache_node *n, return page; } + n->free_touched = 1; list_for_each_entry(page, &n->slabs_free, lru) { - if (!PageSlabPfmemalloc(page)) + if (!PageSlabPfmemalloc(page)) { + *page_is_free = true; return page; + } } return NULL; @@ -2924,17 +2919,26 @@ static noinline struct page *get_valid_first_slab(struct kmem_cache_node *n, static struct page *get_first_slab(struct kmem_cache_node *n, bool pfmemalloc) { struct page *page; + bool page_is_free = false; + assert_spin_locked(&n->list_lock); page = list_first_entry_or_null(&n->slabs_partial, struct page, lru); if (!page) { n->free_touched = 1; page = list_first_entry_or_null(&n->slabs_free, struct page, lru); + if (page) + page_is_free = true; } if (sk_memalloc_socks()) - return get_valid_first_slab(n, page, pfmemalloc); + page = get_valid_first_slab(n, page, &page_is_free, pfmemalloc); + + if (page && page_is_free) { + n->active_slabs++; + n->free_slabs--; + } return page; } @@ -3434,9 +3438,11 @@ static void free_block(struct kmem_cache *cachep, void **objpp, STATS_DEC_ACTIVE(cachep); /* fixup slab chains */ - if (page->active == 0) + if (page->active == 0) { list_add(&page->lru, &n->slabs_free); - else { + n->free_slabs++; + n->active_slabs--; + } else { /* Unconditionally move a slab to the end of the * partial list on free - maximum time for the * other objects to be freed, too. @@ -3450,7 +3456,7 @@ static void free_block(struct kmem_cache *cachep, void **objpp, page = list_last_entry(&n->slabs_free, struct page, lru); list_move(&page->lru, list); - n->num_slabs--; + n->free_slabs--; } } @@ -4102,43 +4108,21 @@ static void cache_reap(struct work_struct *w) #ifdef CONFIG_SLABINFO void get_slabinfo(struct kmem_cache *cachep, struct slabinfo *sinfo) { - struct page *page; - unsigned long active_objs; - unsigned long num_objs; - unsigned long active_slabs = 0; - unsigned long num_slabs, free_objects = 0, shared_avail = 0; - unsigned long num_slabs_partial = 0, num_slabs_free = 0; - unsigned long num_slabs_full = 0; - const char *name; - char *error = NULL; + unsigned long active_objs, num_objs, active_slabs; + unsigned long num_slabs = 0, free_objs = 0, shared_avail = 0; + unsigned long num_slabs_free = 0; int node; struct kmem_cache_node *n; - active_objs = 0; - num_slabs = 0; for_each_kmem_cache_node(cachep, node, n) { - check_irq_on(); spin_lock_irq(&n->list_lock); - num_slabs += n->num_slabs; + num_slabs += n->active_slabs + n->free_slabs; + num_slabs_free += n->free_slabs; - list_for_each_entry(page, &n->slabs_partial, lru) { - if (page->active == cachep->num && !error) - error = "slabs_partial accounting error"; - if (!page->active && !error) - error = "slabs_partial accounting error"; - active_objs += page->active; - num_slabs_partial++; - } + free_objs += n->free_objects; - list_for_each_entry(page, &n->slabs_free, lru) { - if (page->active && !error) - error = "slabs_free accounting error"; - num_slabs_free++; - } - - free_objects += n->free_objects; if (n->shared) shared_avail += n->shared->avail; @@ -4146,15 +4130,8 @@ void get_slabinfo(struct kmem_cache *cachep, struct slabinfo *sinfo) } num_objs = num_slabs * cachep->num; active_slabs = num_slabs - num_slabs_free; - num_slabs_full = num_slabs - (num_slabs_partial + num_slabs_free); - active_objs += (num_slabs_full * cachep->num); - if (num_objs - active_objs != free_objects && !error) - error = "free_objects accounting error"; - - name = cachep->name; - if (error) - pr_err("slab: cache %s error: %s\n", name, error); + active_objs = num_objs - free_objs; sinfo->active_objs = active_objs; sinfo->num_objs = num_objs; diff --git a/mm/slab.h b/mm/slab.h index 699b072dc46e..26123c512fee 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -447,7 +447,8 @@ struct kmem_cache_node { struct list_head slabs_partial; /* partial list first, better asm code */ struct list_head slabs_full; struct list_head slabs_free; - unsigned long num_slabs; + unsigned long active_slabs; /* length of slabs_partial+slabs_full */ + unsigned long free_slabs; /* length of slabs_free */ unsigned long free_objects; unsigned int free_limit; unsigned int colour_next; /* Per-node cache coloring */ -- GitLab