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Date: Thu, 2 Nov 2017 20:15:55 +0900 From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> To: mhocko@...nel.org, aarcange@...hat.com Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 1/2] mm,oom: Move last second allocation to inside the OOM killer. Michal Hocko wrote: > I would really suggest you to stick with the changelog I have suggested. > Well, I think that this patch needs to clarify why using ALLOC_WMARK_HIGH. > On Wed 01-11-17 20:54:27, Tetsuo Handa wrote: > [...] > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index 26add8a..118ecdb 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -870,6 +870,19 @@ static void oom_kill_process(struct oom_control *oc, const char *message) > > } > > task_unlock(p); > > > > + /* > > + * Try really last second allocation attempt after we selected an OOM > > + * victim, for somebody might have managed to free memory while we were > > + * selecting an OOM victim which can take quite some time. > > + */ > > + if (oc->ac) { > > + oc->page = alloc_pages_before_oomkill(oc); > > I would stick the oc->ac check inside alloc_pages_before_oomkill. OK. > > > + if (oc->page) { > > + put_task_struct(p); > > + return; > > + } > > + } > > + > > if (__ratelimit(&oom_rs)) > > dump_header(oc, p); > > > > @@ -1081,6 +1094,16 @@ bool out_of_memory(struct oom_control *oc) > > select_bad_process(oc); > > /* Found nothing?!?! Either we hang forever, or we panic. */ > > if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) { > > + /* > > + * Try really last second allocation attempt, for somebody > > + * might have managed to free memory while we were trying to > > + * find an OOM victim. > > + */ > > + if (oc->ac) { > > + oc->page = alloc_pages_before_oomkill(oc); > > + if (oc->page) > > + return true; > > + } > > dump_header(oc, NULL); > > panic("Out of memory and no killable processes...\n"); > > } > > Also, is there any strong reason to not do the last allocation after > select_bad_process rather than having two call sites? I would understand > that if you wanted to catch for_each_thread inside oom_kill_process but > you are not doing that. Unfortunately, we will after all have two call sites because we have sysctl_oom_kill_allocating_task path. V2 patch follows. Andrea, will you check that your intent of using high watermark for last second allocation attempt in the change log is correct?
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