From 3a246fba6bea9dfc79cbe8581b560180fba7d210 Mon Sep 17 00:00:00 2001 From: Vladimir Davydov Date: Thu, 26 Jun 2014 10:42:31 +1000 Subject: [PATCH] slab: do not keep free objects/slabs on dead memcg caches Since a dead memcg cache is destroyed only after the last slab allocated to it is freed, we must disable caching of free objects/slabs for such caches, otherwise they will be hanging around forever. For SLAB that means we must disable per cpu free object arrays and make free_block always discard empty slabs irrespective of node's free_limit. To disable per cpu arrays, we free them on kmem_cache_shrink (see drain_cpu_caches -> do_drain) and make __cache_free fall back to free_block if there is no per cpu array. Also, we have to disable allocation of per cpu arrays on cpu hotplug for dead caches (see cpuup_prepare, __do_tune_cpucache). After we disabled free objects/slabs caching, there is no need to reap those caches periodically. Moreover, it will only result in slowdown. So we also make cache_reap skip then. Signed-off-by: Vladimir Davydov Cc: Michal Hocko Cc: Johannes Weiner Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton --- mm/slab.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/mm/slab.c b/mm/slab.c index d60da1dd5e89..f27ad3741de8 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -1262,6 +1262,9 @@ static int cpuup_prepare(long cpu) struct array_cache *shared = NULL; struct array_cache **alien = NULL; + if (memcg_cache_dead(cachep)) + continue; + nc = alloc_arraycache(node, cachep->limit, cachep->batchcount, GFP_KERNEL); if (!nc) @@ -2462,11 +2465,18 @@ static void do_drain(void *arg) check_irq_off(); ac = cpu_cache_get(cachep); + if (!ac) + return; + n = get_node(cachep, node); spin_lock(&n->list_lock); free_block(cachep, ac->entry, ac->avail, node); spin_unlock(&n->list_lock); ac->avail = 0; + if (memcg_cache_dead(cachep)) { + cachep->array[smp_processor_id()] = NULL; + kfree(ac); + } } static void drain_cpu_caches(struct kmem_cache *cachep) @@ -3417,7 +3427,8 @@ static void free_block(struct kmem_cache *cachep, void **objpp, int nr_objects, /* fixup slab chains */ if (page->active == 0) { - if (n->free_objects > n->free_limit) { + if (n->free_objects > n->free_limit || + memcg_cache_dead(cachep)) { n->free_objects -= cachep->num; /* No need to drop any previously held * lock here, even if we have a off-slab slab @@ -3511,6 +3522,17 @@ static inline void __cache_free(struct kmem_cache *cachep, void *objp, kmemcheck_slab_free(cachep, objp, cachep->object_size); +#ifdef CONFIG_MEMCG_KMEM + if (unlikely(!ac)) { + int nodeid = page_to_nid(virt_to_page(objp)); + + spin_lock(&cachep->node[nodeid]->list_lock); + free_block(cachep, &objp, 1, nodeid); + spin_unlock(&cachep->node[nodeid]->list_lock); + return; + } +#endif + /* * Skip calling cache_free_alien() when the platform is not numa. * This will avoid cache misses that happen while accessing slabp (which @@ -3851,6 +3873,9 @@ static int __do_tune_cpucache(struct kmem_cache *cachep, int limit, struct ccupdate_struct *new; int i; + if (memcg_cache_dead(cachep)) + return 0; + new = kzalloc(sizeof(*new) + nr_cpu_ids * sizeof(struct array_cache *), gfp); if (!new) @@ -4042,6 +4067,9 @@ static void cache_reap(struct work_struct *w) list_for_each_entry(searchp, &slab_caches, list) { check_irq_on(); + if (memcg_cache_dead(searchp)) + continue; + /* * We only take the node lock if absolutely necessary and we * have established with reasonable certainty that -- 2.39.5