74 lines
2.8 KiB
Diff
74 lines
2.8 KiB
Diff
From: Vladimir Davydov <vdavydov.dev@gmail.com>
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Date: Sat, 1 Oct 2016 16:39:09 +0300
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Subject: mm: memcontrol: use special workqueue for creating per-memcg caches
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Origin: https://patchwork.kernel.org/patch/9361853/
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Bug: https://bugzilla.kernel.org/show_bug.cgi?id=172981
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Creating a lot of cgroups at the same time might stall all worker
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threads with kmem cache creation works, because kmem cache creation is
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done with the slab_mutex held. The problem was amplified by commits
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801faf0db894 ("mm/slab: lockless decision to grow cache") in case of
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SLAB and 81ae6d03952c ("mm/slub.c: replace kick_all_cpus_sync() with
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synchronize_sched() in kmem_cache_shrink()") in case of SLUB, which
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increased the maximal time the slab_mutex can be held.
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To prevent that from happening, let's use a special ordered single
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threaded workqueue for kmem cache creation. This shouldn't introduce any
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functional changes regarding how kmem caches are created, as the work
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function holds the global slab_mutex during its whole runtime anyway,
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making it impossible to run more than one work at a time. By using a
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single threaded workqueue, we just avoid creating a thread per each
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work. Ordering is required to avoid a situation when a cgroup's work is
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put off indefinitely because there are other cgroups to serve, in other
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words to guarantee fairness.
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Link: https://bugzilla.kernel.org/show_bug.cgi?id=172981
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Signed-off-by: Vladimir Davydov <vdavydov.dev@gmail.com>
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Reported-by: Doug Smythies <dsmythies@telus.net>
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Cc: Christoph Lameter <cl@linux.com>
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Cc: David Rientjes <rientjes@google.com>
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Cc: Johannes Weiner <hannes@cmpxchg.org>
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Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
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Cc: Michal Hocko <mhocko@kernel.org>
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Cc: Pekka Enberg <penberg@kernel.org>
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Acked-by: Michal Hocko <mhocko@suse.com>
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---
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--- a/mm/memcontrol.c
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+++ b/mm/memcontrol.c
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@@ -2232,6 +2232,8 @@ 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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+
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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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@@ -2263,7 +2265,7 @@ static void __memcg_schedule_kmem_cache_
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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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@@ -5811,6 +5813,17 @@ 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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+
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hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
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for_each_possible_cpu(cpu)
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