From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> If memcg OOM events in different domains are pending, already OOM-killed threads needlessly wait for pending memcg OOM events in different domains. An out_of_memory() call is slow because it involves printk(). With slow serial consoles, out_of_memory() might take more than a second. Therefore, allowing killed processes to quickly call mmput() from exit_mm() from do_exit() will help calling __mmput() (which can reclaim more memory than the OOM reaper can reclaim) quickly. Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 90eb2e2..a7d3ba9 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1389,14 +1389,19 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, }; bool ret = true; - mutex_lock(&oom_lock); - /* - * multi-threaded tasks might race with oom_reaper and gain - * MMF_OOM_SKIP before reaching out_of_memory which can lead - * to out_of_memory failure if the task is the last one in - * memcg which would be a false possitive failure reported + * Multi-threaded tasks might race with oom_reaper() and gain + * MMF_OOM_SKIP before reaching out_of_memory(). But if current + * thread was already killed or is ready to terminate, there is + * no need to call out_of_memory() nor wait for oom_reaoer() to + * set MMF_OOM_SKIP. These three checks minimize possibility of + * needlessly calling out_of_memory() and try to call exit_mm() + * as soon as possible. */ + if (mutex_lock_killable(&oom_lock)) + return true; + if (fatal_signal_pending(current)) + goto unlock; if (tsk_is_oom_victim(current)) goto unlock; -- 1.8.3.1
