From: Michal Hocko <mhocko@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Rik van Riel <riel@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm, vmscan: do not loop on too_many_isolated for ever
Date: Thu, 20 Jul 2017 08:56:26 +0200 [thread overview]
Message-ID: <20170720065625.GB9058@dhcp22.suse.cz> (raw)
In-Reply-To: <20170719152014.53a861c57bcb636d6cd9d002@linux-foundation.org>
On Wed 19-07-17 15:20:14, Andrew Morton wrote:
> On Mon, 10 Jul 2017 09:48:42 +0200 Michal Hocko <mhocko@kernel.org> wrote:
>
> > From: Michal Hocko <mhocko@suse.com>
> >
> > Tetsuo Handa has reported [1][2][3]that direct reclaimers might get stuck
> > in too_many_isolated loop basically for ever because the last few pages
> > on the LRU lists are isolated by the kswapd which is stuck on fs locks
> > when doing the pageout or slab reclaim. This in turn means that there is
> > nobody to actually trigger the oom killer and the system is basically
> > unusable.
> >
> > too_many_isolated has been introduced by 35cd78156c49 ("vmscan: throttle
> > direct reclaim when too many pages are isolated already") to prevent
> > from pre-mature oom killer invocations because back then no reclaim
> > progress could indeed trigger the OOM killer too early. But since the
> > oom detection rework 0a0337e0d1d1 ("mm, oom: rework oom detection")
> > the allocation/reclaim retry loop considers all the reclaimable pages
> > and throttles the allocation at that layer so we can loosen the direct
> > reclaim throttling.
> >
> > Make shrink_inactive_list loop over too_many_isolated bounded and returns
> > immediately when the situation hasn't resolved after the first sleep.
> > Replace congestion_wait by a simple schedule_timeout_interruptible because
> > we are not really waiting on the IO congestion in this path.
> >
> > Please note that this patch can theoretically cause the OOM killer to
> > trigger earlier while there are many pages isolated for the reclaim
> > which makes progress only very slowly. This would be obvious from the oom
> > report as the number of isolated pages are printed there. If we ever hit
> > this should_reclaim_retry should consider those numbers in the evaluation
> > in one way or another.
>
> Need to figure out which kernels to patch. Maybe just 4.13-rc after a
> week or two?
I do not think we need to rush it and the next merge window should be
just OK.
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1713,9 +1713,15 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
> > int file = is_file_lru(lru);
> > struct pglist_data *pgdat = lruvec_pgdat(lruvec);
> > struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
> > + bool stalled = false;
> >
> > while (unlikely(too_many_isolated(pgdat, file, sc))) {
> > - congestion_wait(BLK_RW_ASYNC, HZ/10);
> > + if (stalled)
> > + return 0;
> > +
> > + /* wait a bit for the reclaimer. */
> > + schedule_timeout_interruptible(HZ/10);
>
> a) if this task has signal_pending(), this falls straight through
> and I suspect the code breaks?
It will not break. It will return to the allocation path more quickly
but no over-reclaim will happen and it will/should get throttled there.
So nothing critical.
> b) replacing congestion_wait() with schedule_timeout_interruptible()
> means this task no longer contributes to load average here and it's
> a (slightly) user-visible change.
you are right. I am not sure it matters but it might be visible.
> c) msleep_interruptible() is nicer
>
> d) IOW, methinks we should be using msleep() here?
OK, I do not have objections. Are you going to squash this in or want a
separate patch explaining all the above?
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-07-20 6:56 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-10 7:48 [PATCH] mm, vmscan: do not loop on too_many_isolated for ever Michal Hocko
2017-07-10 13:16 ` Vlastimil Babka
2017-07-10 13:58 ` Rik van Riel
2017-07-10 16:58 ` Johannes Weiner
2017-07-10 17:09 ` Michal Hocko
2017-07-19 22:20 ` Andrew Morton
2017-07-20 6:56 ` Michal Hocko [this message]
2017-07-21 23:01 ` Andrew Morton
2017-07-24 6:50 ` Michal Hocko
2017-07-20 1:54 ` Hugh Dickins
2017-07-20 10:44 ` Tetsuo Handa
2017-07-24 7:01 ` Hugh Dickins
2017-07-24 11:12 ` Tetsuo Handa
2017-07-20 13:22 ` Michal Hocko
2017-07-24 7:03 ` Hugh Dickins
-- strict thread matches above, loose matches on Subject: below --
2017-03-07 13:30 Michal Hocko
2017-03-07 19:52 ` Rik van Riel
2017-03-08 9:21 ` Michal Hocko
2017-03-08 15:54 ` Rik van Riel
2017-03-09 9:12 ` Michal Hocko
2017-03-09 14:16 ` Rik van Riel
2017-03-09 14:59 ` Michal Hocko
2017-03-09 18:05 ` Johannes Weiner
2017-03-09 22:18 ` Rik van Riel
2017-03-10 10:27 ` Michal Hocko
2017-03-10 10:20 ` Michal Hocko
2017-03-10 11:44 ` Tetsuo Handa
2017-03-21 10:37 ` Tetsuo Handa
2017-04-23 10:24 ` Tetsuo Handa
2017-04-24 12:39 ` Stanislaw Gruszka
2017-04-24 13:06 ` Tetsuo Handa
2017-04-25 6:33 ` Stanislaw Gruszka
2017-06-30 0:14 ` Tetsuo Handa
2017-06-30 13:32 ` Michal Hocko
2017-06-30 15:59 ` Tetsuo Handa
2017-06-30 16:19 ` Michal Hocko
2017-07-01 11:43 ` Tetsuo Handa
2017-07-05 8:19 ` Michal Hocko
2017-07-05 8:20 ` Michal Hocko
2017-07-06 10:48 ` Tetsuo Handa
2017-03-09 14:31 ` Mel Gorman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170720065625.GB9058@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=penguin-kernel@I-love.SAKURA.ne.jp \
--cc=riel@redhat.com \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).