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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