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

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Message-ID: <20211130172754.GS3366@techsingularity.net>
Date:   Tue, 30 Nov 2021 17:27:54 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Alexey Avramov <hakavlad@...ox.lv>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...riel.com>,
        Mike Galbraith <efault@....de>,
        Darrick Wong <djwong@...nel.org>, regressions@...ts.linux.dev,
        Linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] mm: vmscan: Reduce throttling due to a failure to
 make progress

On Wed, Dec 01, 2021 at 01:03:48AM +0900, Alexey Avramov wrote:
> I tested this [1] patch on top of 5.16-rc2. It's the same test with 10 tails.
> 
> - with noswap
> 
> Summary:
> 
> 2021-11-30 23:32:36,890: Stall times for the last 548.6s:
> 2021-11-30 23:32:36,890: -----------
> 2021-11-30 23:32:36,891: some cpu     3.7s, avg 0.7%
> 2021-11-30 23:32:36,891: -----------
> 2021-11-30 23:32:36,891: some io      187.6s, avg 34.2%
> 2021-11-30 23:32:36,891: full io      178.3s, avg 32.5%
> 2021-11-30 23:32:36,891: -----------
> 2021-11-30 23:32:36,892: some memory  392.2s, avg 71.5%
> 2021-11-30 23:32:36,892: full memory  390.7s, avg 71.2%
> 
> full psi:
> https://raw.githubusercontent.com/hakavlad/cache-tests/main/516-reclaim-throttle/516-rc2/patch5/noswap/psi
> 
> mem:
> https://raw.githubusercontent.com/hakavlad/cache-tests/main/516-reclaim-throttle/516-rc2/patch5/noswap/mem
> 

Ok, taking just noswap in isolation, this is what I saw when running
firefox + youtube vido and running tail /dev/zero 10 times in a row

2021-11-30 17:10:11,817: =================================
2021-11-30 17:10:11,817: Peak values:  avg10  avg60 avg300
2021-11-30 17:10:11,817: -----------  ------ ------ ------
2021-11-30 17:10:11,817: some cpu       1.00   0.96   0.56
2021-11-30 17:10:11,817: -----------  ------ ------ ------
2021-11-30 17:10:11,817: some io        0.24   0.06   0.04
2021-11-30 17:10:11,817: full io        0.24   0.06   0.01
2021-11-30 17:10:11,817: -----------  ------ ------ ------
2021-11-30 17:10:11,817: some memory    2.48   0.51   0.38
2021-11-30 17:10:11,817: full memory    2.48   0.51   0.37
2021-11-30 17:10:11,817: =================================
2021-11-30 17:10:11,817: Stall times for the last 53.7s:
2021-11-30 17:10:11,817: -----------
2021-11-30 17:10:11,817: some cpu     0.4s, avg 0.8%
2021-11-30 17:10:11,817: -----------
2021-11-30 17:10:11,817: some io      0.1s, avg 0.2%
2021-11-30 17:10:11,817: full io      0.1s, avg 0.2%
2021-11-30 17:10:11,817: -----------
2021-11-30 17:10:11,817: some memory  0.3s, avg 0.6%
2021-11-30 17:10:11,817: full memory  0.3s, avg 0.6%

Obviously a fairly different experience and most likely due to the
underlying storage.

Can you run the same test but after doing this

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

and send me the trace.out file please?

-- 
Mel Gorman
SUSE Labs