From 65c3376aaca96c66aa76014aaf430398964b68cb Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Mon, 14 Apr 2008 19:11:40 +0300 Subject: [PATCH] slub: Fallback to minimal order during slab page allocation If any higher order allocation fails then fall back the smallest order necessary to contain at least one object. This enables fallback for all allocations to order 0 pages. The fallback will waste more memory (objects will not fit neatly) and the fallback slabs will be not as efficient as larger slabs since they contain less objects. Note that SLAB also depends on order 1 allocations for some slabs that waste too much memory if forced into PAGE_SIZE'd page. SLUB now can now deal with failing order 1 allocs which SLAB cannot do. Add a new field min that will contain the objects for the smallest possible order for a slab cache. Signed-off-by: Christoph Lameter Signed-off-by: Pekka Enberg --- include/linux/slub_def.h | 2 ++ mm/slub.c | 39 ++++++++++++++++++++++++++++----------- 2 files changed, 30 insertions(+), 11 deletions(-) diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h index 4236b5dee81..71e43a12ebb 100644 --- a/include/linux/slub_def.h +++ b/include/linux/slub_def.h @@ -29,6 +29,7 @@ enum stat_item { DEACTIVATE_TO_HEAD, /* Cpu slab was moved to the head of partials */ DEACTIVATE_TO_TAIL, /* Cpu slab was moved to the tail of partials */ DEACTIVATE_REMOTE_FREES,/* Slab contained remotely freed objects */ + ORDER_FALLBACK, /* Number of times fallback was necessary */ NR_SLUB_STAT_ITEMS }; struct kmem_cache_cpu { @@ -81,6 +82,7 @@ struct kmem_cache { /* Allocation and freeing of slabs */ struct kmem_cache_order_objects max; + struct kmem_cache_order_objects min; gfp_t allocflags; /* gfp flags to use on each alloc */ int refcount; /* Refcount for slab cache destroy */ void (*ctor)(struct kmem_cache *, void *); diff --git a/mm/slub.c b/mm/slub.c index c8514e93ffd..35c22d940ba 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1113,28 +1113,43 @@ static inline void dec_slabs_node(struct kmem_cache *s, int node, /* * Slab allocation and freeing */ +static inline struct page *alloc_slab_page(gfp_t flags, int node, + struct kmem_cache_order_objects oo) +{ + int order = oo_order(oo); + + if (node == -1) + return alloc_pages(flags, order); + else + return alloc_pages_node(node, flags, order); +} + static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) { struct page *page; struct kmem_cache_order_objects oo = s->oo; - int order = oo_order(oo); - int pages = 1 << order; flags |= s->allocflags; - if (node == -1) - page = alloc_pages(flags, order); - else - page = alloc_pages_node(node, flags, order); - - if (!page) - return NULL; + page = alloc_slab_page(flags | __GFP_NOWARN | __GFP_NORETRY, node, + oo); + if (unlikely(!page)) { + oo = s->min; + /* + * Allocation may have failed due to fragmentation. + * Try a lower order alloc if possible + */ + page = alloc_slab_page(flags, node, oo); + if (!page) + return NULL; + stat(get_cpu_slab(s, raw_smp_processor_id()), ORDER_FALLBACK); + } page->objects = oo_objects(oo); mod_zone_page_state(page_zone(page), (s->flags & SLAB_RECLAIM_ACCOUNT) ? NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE, - pages); + 1 << oo_order(oo)); return page; } @@ -2347,6 +2362,7 @@ static int calculate_sizes(struct kmem_cache *s) * Determine the number of objects per slab */ s->oo = oo_make(order, size); + s->min = oo_make(get_order(size), size); if (oo_objects(s->oo) > oo_objects(s->max)) s->max = s->oo; @@ -4163,7 +4179,7 @@ STAT_ATTR(DEACTIVATE_EMPTY, deactivate_empty); STAT_ATTR(DEACTIVATE_TO_HEAD, deactivate_to_head); STAT_ATTR(DEACTIVATE_TO_TAIL, deactivate_to_tail); STAT_ATTR(DEACTIVATE_REMOTE_FREES, deactivate_remote_frees); - +STAT_ATTR(ORDER_FALLBACK, order_fallback); #endif static struct attribute *slab_attrs[] = { @@ -4216,6 +4232,7 @@ static struct attribute *slab_attrs[] = { &deactivate_to_head_attr.attr, &deactivate_to_tail_attr.attr, &deactivate_remote_frees_attr.attr, + &order_fallback_attr.attr, #endif NULL }; -- 2.20.1