From 1af8efe965676ab30d6c8a5b1fccc9229f339a3b Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Tue, 26 Jul 2011 16:08:24 -0700 Subject: [PATCH] memcg: change memcg_oom_mutex to spinlock memcg_oom_mutex is used to protect memcg OOM path and eventfd interface for oom_control. None of the critical sections which it protects sleep (eventfd_signal works from atomic context and the rest are simple linked list resp. oom_lock atomic operations). Mutex is also too heavyweight for those code paths because it triggers a lot of scheduling. It also makes makes convoying effects more visible when we have a big number of oom killing because we take the lock mutliple times during mem_cgroup_handle_oom so we have multiple places where many processes can sleep. Signed-off-by: Michal Hocko Cc: Balbir Singh Cc: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 95d6c256b54c..c0b065ec1571 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1725,7 +1725,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem, /* * Check OOM-Killer is already running under our hierarchy. * If someone is running, return false. - * Has to be called with memcg_oom_mutex + * Has to be called with memcg_oom_lock */ static bool mem_cgroup_oom_lock(struct mem_cgroup *mem) { @@ -1770,7 +1770,7 @@ static bool mem_cgroup_oom_lock(struct mem_cgroup *mem) } /* - * Has to be called with memcg_oom_mutex + * Has to be called with memcg_oom_lock */ static int mem_cgroup_oom_unlock(struct mem_cgroup *mem) { @@ -1802,7 +1802,7 @@ static void mem_cgroup_unmark_under_oom(struct mem_cgroup *mem) atomic_add_unless(&iter->under_oom, -1, 0); } -static DEFINE_MUTEX(memcg_oom_mutex); +static DEFINE_SPINLOCK(memcg_oom_lock); static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq); struct oom_wait_info { @@ -1864,7 +1864,7 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask) mem_cgroup_mark_under_oom(mem); /* At first, try to OOM lock hierarchy under mem.*/ - mutex_lock(&memcg_oom_mutex); + spin_lock(&memcg_oom_lock); locked = mem_cgroup_oom_lock(mem); /* * Even if signal_pending(), we can't quit charge() loop without @@ -1876,7 +1876,7 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask) need_to_kill = false; if (locked) mem_cgroup_oom_notify(mem); - mutex_unlock(&memcg_oom_mutex); + spin_unlock(&memcg_oom_lock); if (need_to_kill) { finish_wait(&memcg_oom_waitq, &owait.wait); @@ -1885,11 +1885,11 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask) schedule(); finish_wait(&memcg_oom_waitq, &owait.wait); } - mutex_lock(&memcg_oom_mutex); + spin_lock(&memcg_oom_lock); if (locked) mem_cgroup_oom_unlock(mem); memcg_wakeup_oom(mem); - mutex_unlock(&memcg_oom_mutex); + spin_unlock(&memcg_oom_lock); mem_cgroup_unmark_under_oom(mem); @@ -4553,7 +4553,7 @@ static int mem_cgroup_oom_register_event(struct cgroup *cgrp, if (!event) return -ENOMEM; - mutex_lock(&memcg_oom_mutex); + spin_lock(&memcg_oom_lock); event->eventfd = eventfd; list_add(&event->list, &memcg->oom_notify); @@ -4561,7 +4561,7 @@ static int mem_cgroup_oom_register_event(struct cgroup *cgrp, /* already in OOM ? */ if (atomic_read(&memcg->under_oom)) eventfd_signal(eventfd, 1); - mutex_unlock(&memcg_oom_mutex); + spin_unlock(&memcg_oom_lock); return 0; } @@ -4575,7 +4575,7 @@ static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp, BUG_ON(type != _OOM_TYPE); - mutex_lock(&memcg_oom_mutex); + spin_lock(&memcg_oom_lock); list_for_each_entry_safe(ev, tmp, &mem->oom_notify, list) { if (ev->eventfd == eventfd) { @@ -4584,7 +4584,7 @@ static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp, } } - mutex_unlock(&memcg_oom_mutex); + spin_unlock(&memcg_oom_lock); } static int mem_cgroup_oom_control_read(struct cgroup *cgrp, -- GitLab