linux-kernel - Re: [PATCH v4 1/1] mm: vmscan: Reduce throttling due to a failure to make progress'

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Date:   Wed, 23 Feb 2022 12:50:02 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Shuang Zhai <szhai2@...rochester.edu>
Cc:     akpm@...ux-foundation.org, djwong@...nel.org, efault@....de,
        hakavlad@...ox.lv, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, mhocko@...e.com,
        regressions@...ts.linux.dev, riel@...riel.com, vbabka@...e.cz
Subject: Re: [PATCH v4 1/1] mm: vmscan: Reduce throttling due to a failure to
 make progress'

On Tue, Feb 22, 2022 at 12:27:31PM -0500, Shuang Zhai wrote:
> Mel Gorman wrote:
> > On Mon, Feb 14, 2022 at 04:10:50PM -0500, Shuang Zhai wrote:
> > > Hi Mel,
> > > 
> > > Mel Gorman wrote:
> > > >
> > > > Mike Galbraith, Alexey Avramov and Darrick Wong all reported similar
> > > > problems due to reclaim throttling for excessive lengths of time.
> > > > In Alexey's case, a memory hog that should go OOM quickly stalls for
> > > > several minutes before stalling. In Mike and Darrick's cases, a small
> > > > memcg environment stalled excessively even though the system had enough
> > > > memory overall.
> > > >
> > > 
> > > I recently found a regression when I tested MGLRU with fio on Linux
> > > 5.16-rc6 [1]. After this patch was applied, I re-ran the test with Linux
> > > 5.16, but the regression has not been fixed yet. 
> > > 
> > 
> > Am I correct in thinging that this only happens with MGLRU?
> 
> Sorry about the confusion and let me clarify on this. The regression happens
> on upstream Linux with the default page replacement mechanism.

Ok, the fio command for me simply exits with an error and even if it didn't
the test machine I have with persistent memory does not have enough pmem
to trigger memory reclaim issues with fio. Can you do the following please?

# echo 1 > vmscan/mm_vmscan_throttled/enable
# cat /sys/kernel/debug/tracing/trace_pipe > trace.out

and run the test? Compress trace.out with xz and send it to me by mail.
If the trace is too large, send as much as you can.

-- 
Mel Gorman
SUSE Labs