Re: [PATCH 1/2] mm: add per-zone lru list stat

From	Mel Gorman <mgorman@suse.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/2] mm: add per-zone lru list stat
Date	2016-07-20 13:00 +0200
Message-ID	<rWXom-jn-23@gated-at.bofh.it> (permalink)
References	<rWFB8-5U4-19@gated-at.bofh.it> <rWGnv-6pc-9@gated-at.bofh.it> <rWNoZ-2vg-7@gated-at.bofh.it>
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On Wed, Jul 20, 2016 at 09:16:24AM +0900, Minchan Kim wrote:
> On Tue, Jul 19, 2016 at 05:48:57PM +0100, Mel Gorman wrote:
> > On Wed, Jul 20, 2016 at 12:50:32AM +0900, Minchan Kim wrote:
> > > While I did stress test with hackbench, I got OOM message frequently
> > > which didn't ever happen in zone-lru.
> > > 
> > 
> > This one also showed pgdat going unreclaimable early. Have you tried any
> > of the three oom-related patches I sent to Joonsoo to see what impact,
> > if any, it had?
> 
> Before the result, I want to say goal of this patch, again.
> Without per-zone lru stat, it's really hard to debug OOM problem in
> multiple zones system so regardless of solving the problem, we should add
> per-zone lru stat for debuggability of OOM which has been never perfect
> solution, ever.
> 

That's not in dispute, I simply wanted to know the impact.

> The result is not OOM but hackbench stalls forever.

Ok, that points to both the premature marking pgdats as unreclaimable
and the inactive rotation are both problems.

I have a series prepared that may or may not address the problem. I'm
trying to reproduce the OOM killer on a 32-bit KVM but so far so luck.
If I fail to reproduce it then I cannot tell if the series has an impact
and may have to post it and hope you and Joonsoo can test it.

-- 
Mel Gorman
SUSE Labs

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[PATCH 1/2] mm: add per-zone lru list stat Minchan Kim <minchan@kernel.org> - 2016-07-19 18:00 +0200
  [PATCH 2/2] mm: consider per-zone inactive ratio to deactivate Minchan Kim <minchan@kernel.org> - 2016-07-19 18:00 +0200
  Re: [PATCH 1/2] mm: add per-zone lru list stat Mel Gorman <mgorman@suse.de> - 2016-07-19 18:50 +0200
    Re: [PATCH 1/2] mm: add per-zone lru list stat Minchan Kim <minchan@kernel.org> - 2016-07-20 02:20 +0200
      Re: [PATCH 1/2] mm: add per-zone lru list stat Mel Gorman <mgorman@suse.de> - 2016-07-20 13:00 +0200

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