From 76b342bdc71badea2cbac7bf6590aa86e895c507 Mon Sep 17 00:00:00 2001 From: Joonsoo Kim Date: Thu, 19 May 2016 17:10:26 -0700 Subject: [PATCH] mm/slab: separate cache_grow() to two parts This is a preparation step to implement lockless allocation path when there is no free objects in kmem_cache. What we'd like to do here is to refill cpu cache without holding a node lock. To accomplish this purpose, refill should be done after new slab allocation but before attaching the slab to the management list. So, this patch separates cache_grow() to two parts, allocation and attaching to the list in order to add some code inbetween them in the following patch. Signed-off-by: Joonsoo Kim Cc: Jesper Dangaard Brouer Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slab.c | 74 ++++++++++++++++++++++++++++++++++++++----------------- 1 file changed, 52 insertions(+), 22 deletions(-) diff --git a/mm/slab.c b/mm/slab.c index b303c04c1565..8c4db214b05b 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -213,6 +213,11 @@ static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list); static int enable_cpucache(struct kmem_cache *cachep, gfp_t gfp); static void cache_reap(struct work_struct *unused); +static inline void fixup_objfreelist_debug(struct kmem_cache *cachep, + void **list); +static inline void fixup_slab_list(struct kmem_cache *cachep, + struct kmem_cache_node *n, struct page *page, + void **list); static int slab_early_init = 1; #define INDEX_NODE kmalloc_index(sizeof(struct kmem_cache_node)) @@ -1810,7 +1815,7 @@ static size_t calculate_slab_order(struct kmem_cache *cachep, /* * Needed to avoid possible looping condition - * in cache_grow() + * in cache_grow_begin() */ if (OFF_SLAB(freelist_cache)) continue; @@ -2556,7 +2561,8 @@ static void slab_map_pages(struct kmem_cache *cache, struct page *page, * Grow (by 1) the number of slabs within a cache. This is called by * kmem_cache_alloc() when there are no active objs left in a cache. */ -static int cache_grow(struct kmem_cache *cachep, gfp_t flags, int nodeid) +static struct page *cache_grow_begin(struct kmem_cache *cachep, + gfp_t flags, int nodeid) { void *freelist; size_t offset; @@ -2622,21 +2628,40 @@ static int cache_grow(struct kmem_cache *cachep, gfp_t flags, int nodeid) if (gfpflags_allow_blocking(local_flags)) local_irq_disable(); - check_irq_off(); - spin_lock(&n->list_lock); - /* Make slab active. */ - list_add_tail(&page->lru, &(n->slabs_free)); - STATS_INC_GROWN(cachep); - n->free_objects += cachep->num; - spin_unlock(&n->list_lock); - return page_node; + return page; + opps1: kmem_freepages(cachep, page); failed: if (gfpflags_allow_blocking(local_flags)) local_irq_disable(); - return -1; + return NULL; +} + +static void cache_grow_end(struct kmem_cache *cachep, struct page *page) +{ + struct kmem_cache_node *n; + void *list = NULL; + + check_irq_off(); + + if (!page) + return; + + INIT_LIST_HEAD(&page->lru); + n = get_node(cachep, page_to_nid(page)); + + spin_lock(&n->list_lock); + if (!page->active) + list_add_tail(&page->lru, &(n->slabs_free)); + else + fixup_slab_list(cachep, n, page, &list); + STATS_INC_GROWN(cachep); + n->free_objects += cachep->num - page->active; + spin_unlock(&n->list_lock); + + fixup_objfreelist_debug(cachep, &list); } #if DEBUG @@ -2847,6 +2872,7 @@ static void *cache_alloc_refill(struct kmem_cache *cachep, gfp_t flags) struct array_cache *ac; int node; void *list = NULL; + struct page *page; check_irq_off(); node = numa_mem_id(); @@ -2874,7 +2900,6 @@ retry: } while (batchcount > 0) { - struct page *page; /* Get slab alloc is to come from. */ page = get_first_slab(n, false); if (!page) @@ -2907,8 +2932,6 @@ alloc_done: fixup_objfreelist_debug(cachep, &list); if (unlikely(!ac->avail)) { - int x; - /* Check if we can use obj in pfmemalloc slab */ if (sk_memalloc_socks()) { void *obj = cache_alloc_pfmemalloc(cachep, n, flags); @@ -2917,14 +2940,18 @@ alloc_done: return obj; } - x = cache_grow(cachep, gfp_exact_node(flags), node); + page = cache_grow_begin(cachep, gfp_exact_node(flags), node); + cache_grow_end(cachep, page); - /* cache_grow can reenable interrupts, then ac could change. */ + /* + * cache_grow_begin() can reenable interrupts, + * then ac could change. + */ ac = cpu_cache_get(cachep); node = numa_mem_id(); /* no objects in sight? abort */ - if (x < 0 && ac->avail == 0) + if (!page && ac->avail == 0) return NULL; if (!ac->avail) /* objects refilled by interrupt? */ @@ -3057,6 +3084,7 @@ static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags) struct zone *zone; enum zone_type high_zoneidx = gfp_zone(flags); void *obj = NULL; + struct page *page; int nid; unsigned int cpuset_mems_cookie; @@ -3092,8 +3120,10 @@ retry: * We may trigger various forms of reclaim on the allowed * set and go into memory reserves if necessary. */ - nid = cache_grow(cache, flags, numa_mem_id()); - if (nid >= 0) { + page = cache_grow_begin(cache, flags, numa_mem_id()); + cache_grow_end(cache, page); + if (page) { + nid = page_to_nid(page); obj = ____cache_alloc_node(cache, gfp_exact_node(flags), nid); @@ -3121,7 +3151,6 @@ static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, struct kmem_cache_node *n; void *obj; void *list = NULL; - int x; VM_BUG_ON(nodeid < 0 || nodeid >= MAX_NUMNODES); n = get_node(cachep, nodeid); @@ -3153,8 +3182,9 @@ retry: must_grow: spin_unlock(&n->list_lock); - x = cache_grow(cachep, gfp_exact_node(flags), nodeid); - if (x >= 0) + page = cache_grow_begin(cachep, gfp_exact_node(flags), nodeid); + cache_grow_end(cachep, page); + if (page) goto retry; return fallback_alloc(cachep, flags); -- 2.20.1