From: David Rientjes <rientjes@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Michal Hocko <mhocko@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, oom: prevent soft lockup on memcg oom for UP systems
Date: Tue, 10 Mar 2020 17:34:53 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.21.2003101724010.197777@chino.kir.corp.google.com> (raw)
In-Reply-To: <20200310171802.128129f6817ef3f77d230ccd@linux-foundation.org>
On Tue, 10 Mar 2020, Andrew Morton wrote:
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -2637,6 +2637,8 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
> > unsigned long reclaimed;
> > unsigned long scanned;
> >
> > + cond_resched();
> > +
> > switch (mem_cgroup_protected(target_memcg, memcg)) {
> > case MEMCG_PROT_MIN:
> > /*
>
>
> Obviously better, but this will still spin wheels until this tasks's
> timeslice expires, and we might want to do something to help ensure
> that the victim runs next (or soon)?
>
We used to have a schedule_timeout_killable(1) to address exactly that
scenario but it was removed in 4.19:
commit 9bfe5ded054b8e28a94c78580f233d6879a00146
Author: Michal Hocko <mhocko@suse.com>
Date: Fri Aug 17 15:49:04 2018 -0700
mm, oom: remove sleep from under oom_lock
This is why we don't see this issue on 4.14 guests but we do on 4.19. I
had assumed the issue Tetsuo reported that resulted in that patch was
still an issue and I preferred to fix the weird UP issue by adding a
cond_resched() that is likely needed for the iteration in
shrink_node_memcg() anyway. Do we care to optimize for UP systems
encountering memcg oom kills? Eh, maybe, but I'm not very interested in
opening up a centithread about this.
> (And why is shrink_node_memcgs compiled in when CONFIG_MEMCG=n?)
>
This guest does have CONFIG_MEMCG enabled, it's a memcg oom condition.
But unrelated to this patch, I think it's just a weird naming for it. The
do-while loop in shrink_node_memcgs() actually uses memcg = NULL for the
non-memcg case and is responsible for calling into page and slab reclaim.
next prev parent reply other threads:[~2020-03-11 0:34 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-10 21:39 [patch] mm, oom: prevent soft lockup on memcg oom for UP systems David Rientjes
2020-03-10 22:05 ` Tetsuo Handa
2020-03-10 22:55 ` David Rientjes
2020-03-11 9:34 ` Tetsuo Handa
2020-03-11 19:38 ` David Rientjes
2020-03-11 22:04 ` Tetsuo Handa
2020-03-11 22:14 ` David Rientjes
2020-03-12 0:12 ` Tetsuo Handa
2020-03-12 18:07 ` David Rientjes
2020-03-12 22:32 ` Andrew Morton
2020-03-16 9:31 ` Michal Hocko
2020-03-16 10:04 ` Tetsuo Handa
2020-03-16 10:14 ` Michal Hocko
2020-03-13 0:15 ` Tetsuo Handa
2020-03-13 22:01 ` David Rientjes
2020-03-13 23:15 ` Tetsuo Handa
2020-03-13 23:32 ` Tetsuo Handa
2020-03-16 23:59 ` David Rientjes
2020-03-17 3:18 ` Tetsuo Handa
2020-03-17 4:09 ` David Rientjes
2020-03-18 0:55 ` [patch v2] " David Rientjes
2020-03-18 9:42 ` Michal Hocko
2020-03-18 21:40 ` David Rientjes
2020-03-18 22:03 ` [patch v3] " David Rientjes
2020-03-19 7:09 ` Michal Hocko
2020-03-12 4:23 ` [patch] " Tetsuo Handa
2020-03-10 22:10 ` Michal Hocko
2020-03-10 23:02 ` David Rientjes
2020-03-11 8:27 ` Michal Hocko
2020-03-11 19:45 ` David Rientjes
2020-03-12 8:32 ` Michal Hocko
2020-03-12 18:20 ` David Rientjes
2020-03-12 20:16 ` Michal Hocko
2020-03-16 9:32 ` Michal Hocko
2020-03-11 0:18 ` Andrew Morton
2020-03-11 0:34 ` David Rientjes [this message]
2020-03-11 8:36 ` Michal Hocko
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