mm: memcontrol: use special workqueue for creating per-memcg caches
commit13583c3d32
upstream. Creating a lot of cgroups at the same time might stall all worker threads with kmem cache creation works, because kmem cache creation is done with the slab_mutex held. The problem was amplified by commits801faf0db8
("mm/slab: lockless decision to grow cache") in case of SLAB and81ae6d0395
("mm/slub.c: replace kick_all_cpus_sync() with synchronize_sched() in kmem_cache_shrink()") in case of SLUB, which increased the maximal time the slab_mutex can be held. To prevent that from happening, let's use a special ordered single threaded workqueue for kmem cache creation. This shouldn't introduce any functional changes regarding how kmem caches are created, as the work function holds the global slab_mutex during its whole runtime anyway, making it impossible to run more than one work at a time. By using a single threaded workqueue, we just avoid creating a thread per each work. Ordering is required to avoid a situation when a cgroup's work is put off indefinitely because there are other cgroups to serve, in other words to guarantee fairness. Link: https://bugzilla.kernel.org/show_bug.cgi?id=172981 Link: http://lkml.kernel.org/r/20161004131417.GC1862@esperanza Signed-off-by: Vladimir Davydov <vdavydov.dev@gmail.com> Reported-by: Doug Smythies <dsmythies@telus.net> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Pekka Enberg <penberg@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -2152,6 +2152,8 @@ struct memcg_kmem_cache_create_work {
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struct work_struct work;
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};
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static struct workqueue_struct *memcg_kmem_cache_create_wq;
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static void memcg_kmem_cache_create_func(struct work_struct *w)
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{
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struct memcg_kmem_cache_create_work *cw =
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@ -2183,7 +2185,7 @@ static void __memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
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cw->cachep = cachep;
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INIT_WORK(&cw->work, memcg_kmem_cache_create_func);
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schedule_work(&cw->work);
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queue_work(memcg_kmem_cache_create_wq, &cw->work);
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}
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static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
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@ -5786,6 +5788,17 @@ static int __init mem_cgroup_init(void)
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{
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int cpu, node;
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#ifndef CONFIG_SLOB
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/*
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* Kmem cache creation is mostly done with the slab_mutex held,
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* so use a special workqueue to avoid stalling all worker
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* threads in case lots of cgroups are created simultaneously.
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*/
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memcg_kmem_cache_create_wq =
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alloc_ordered_workqueue("memcg_kmem_cache_create", 0);
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BUG_ON(!memcg_kmem_cache_create_wq);
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#endif
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hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
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for_each_possible_cpu(cpu)
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