From: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Subject: slub: move synchronize_sched out of slab_mutex on shrink synchronize_sched() is a heavy operation and calling it per each cache owned by a memory cgroup being destroyed may take quite some time. What is worse, it's currently called under the slab_mutex, stalling all works doing cache creation/destruction. Actually, there isn't much point in calling synchronize_sched() for each cache - it's enough to call it just once - after setting cpu_partial for all caches and before shrinking them. This way, we can also move it out of the slab_mutex, which we have to hold for iterating over the slab cache list. Link: https://bugzilla.kernel.org/show_bug.cgi?id=172991 Link: http://lkml.kernel.org/r/0a10d71ecae3db00fb4421bcd3f82bcc911f4be4.1475329751.git.vdavydov.dev@xxxxxxxxx Signed-off-by: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Reported-by: Doug Smythies <dsmythies@xxxxxxxxx> Acked-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slab.c | 4 ++-- mm/slab.h | 2 +- mm/slab_common.c | 27 +++++++++++++++++++++++++-- mm/slob.c | 2 +- mm/slub.c | 19 ++----------------- 5 files changed, 31 insertions(+), 23 deletions(-) diff -puN mm/slab.c~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink mm/slab.c --- a/mm/slab.c~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink +++ a/mm/slab.c @@ -2332,7 +2332,7 @@ out: return nr_freed; } -int __kmem_cache_shrink(struct kmem_cache *cachep, bool deactivate) +int __kmem_cache_shrink(struct kmem_cache *cachep) { int ret = 0; int node; @@ -2352,7 +2352,7 @@ int __kmem_cache_shrink(struct kmem_cach int __kmem_cache_shutdown(struct kmem_cache *cachep) { - return __kmem_cache_shrink(cachep, false); + return __kmem_cache_shrink(cachep); } void __kmem_cache_release(struct kmem_cache *cachep) diff -puN mm/slab.h~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink mm/slab.h --- a/mm/slab.h~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink +++ a/mm/slab.h @@ -146,7 +146,7 @@ static inline unsigned long kmem_cache_f int __kmem_cache_shutdown(struct kmem_cache *); void __kmem_cache_release(struct kmem_cache *); -int __kmem_cache_shrink(struct kmem_cache *, bool); +int __kmem_cache_shrink(struct kmem_cache *); void slab_kmem_cache_release(struct kmem_cache *); struct seq_file; diff -puN mm/slab_common.c~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink mm/slab_common.c --- a/mm/slab_common.c~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink +++ a/mm/slab_common.c @@ -573,6 +573,29 @@ void memcg_deactivate_kmem_caches(struct get_online_cpus(); get_online_mems(); +#ifdef CONFIG_SLUB + /* + * In case of SLUB, we need to disable empty slab caching to + * avoid pinning the offline memory cgroup by freeable kmem + * pages charged to it. SLAB doesn't need this, as it + * periodically purges unused slabs. + */ + mutex_lock(&slab_mutex); + list_for_each_entry(s, &slab_caches, list) { + c = is_root_cache(s) ? cache_from_memcg_idx(s, idx) : NULL; + if (c) { + c->cpu_partial = 0; + c->min_partial = 0; + } + } + mutex_unlock(&slab_mutex); + /* + * kmem_cache->cpu_partial is checked locklessly (see + * put_cpu_partial()). Make sure the change is visible. + */ + synchronize_sched(); +#endif + mutex_lock(&slab_mutex); list_for_each_entry(s, &slab_caches, list) { if (!is_root_cache(s)) @@ -584,7 +607,7 @@ void memcg_deactivate_kmem_caches(struct if (!c) continue; - __kmem_cache_shrink(c, true); + __kmem_cache_shrink(c); arr->entries[idx] = NULL; } mutex_unlock(&slab_mutex); @@ -755,7 +778,7 @@ int kmem_cache_shrink(struct kmem_cache get_online_cpus(); get_online_mems(); kasan_cache_shrink(cachep); - ret = __kmem_cache_shrink(cachep, false); + ret = __kmem_cache_shrink(cachep); put_online_mems(); put_online_cpus(); return ret; diff -puN mm/slob.c~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink mm/slob.c --- a/mm/slob.c~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink +++ a/mm/slob.c @@ -634,7 +634,7 @@ void __kmem_cache_release(struct kmem_ca { } -int __kmem_cache_shrink(struct kmem_cache *d, bool deactivate) +int __kmem_cache_shrink(struct kmem_cache *d) { return 0; } diff -puN mm/slub.c~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink mm/slub.c --- a/mm/slub.c~slub-move-synchronize_sched-out-of-slab_mutex-on-shrink +++ a/mm/slub.c @@ -3883,7 +3883,7 @@ EXPORT_SYMBOL(kfree); * being allocated from last increasing the chance that the last objects * are freed in them. */ -int __kmem_cache_shrink(struct kmem_cache *s, bool deactivate) +int __kmem_cache_shrink(struct kmem_cache *s) { int node; int i; @@ -3895,21 +3895,6 @@ int __kmem_cache_shrink(struct kmem_cach unsigned long flags; int ret = 0; - if (deactivate) { - /* - * Disable empty slabs caching. Used to avoid pinning offline - * memory cgroups by kmem pages that can be freed. - */ - s->cpu_partial = 0; - s->min_partial = 0; - - /* - * s->cpu_partial is checked locklessly (see put_cpu_partial), - * so we have to make sure the change is visible. - */ - synchronize_sched(); - } - flush_all(s); for_each_kmem_cache_node(s, node, n) { INIT_LIST_HEAD(&discard); @@ -3966,7 +3951,7 @@ static int slab_mem_going_offline_callba mutex_lock(&slab_mutex); list_for_each_entry(s, &slab_caches, list) - __kmem_cache_shrink(s, false); + __kmem_cache_shrink(s); mutex_unlock(&slab_mutex); return 0; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
