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

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Date:   Mon, 29 Nov 2021 08:26:55 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Mike Galbraith <efault@....de>
Cc:     Alexey Avramov <hakavlad@...ox.lv>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...riel.com>,
        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 Sun, Nov 28, 2021 at 11:00:59AM +0100, Mike Galbraith wrote:
> On Sun, 2021-11-28 at 04:26 +0900, Alexey Avramov wrote:
> > I will present the results of the new tests here.
> >
> > TLDR;
> > =====
> > No one Mel's patch doesn't prevent stalls in my tests.
> 
> Seems there may be a problem with the THROTTLE_WRITEBACK bits..
> 
> > $ for i in {1..10}; do tail /dev/zero; done
> > -- 1. with noswap
> 
> ..because the bandaid below (made of 8cd7c588 shards) on top of Mel's
> last pulled that one-liner's very pointy fangs.
> 

This disables writeback throttling in most cases as bdi congested is not
updated by the block layer.

-- 
Mel Gorman
SUSE Labs