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

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Date:   Wed, 1 Dec 2021 15:06:13 +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 Wed, Dec 01, 2021 at 02:52:01PM +0100, Mike Galbraith wrote:
> On Wed, 2021-12-01 at 13:01 +0000, Mel Gorman wrote:
> > On Tue, Nov 30, 2021 at 06:59:58PM +0100, Mike Galbraith wrote:
> > > On Tue, 2021-11-30 at 17:27 +0000, Mel Gorman wrote:
> > > >
> > > > Obviously a fairly different experience and most likely due to
> > > > the
> > > > underlying storage.
> > >
> > > I bet a virtual nickle this is the sore spot.
> > >
> >
> > You win a virtual nickle!
> 
> I'm rich I'm rich... oh dang, virtual.
> 
> I went back to 5.15, and confirmed that wait_iff_congested() did not
> ever sleep with the try to eat /dev/zero load.  Nor did it with insane
> overcommit swap storm from hell with as much IO going on as my little
> box is capable of generating, making the surrounding congestion bits
> look.. down right expendable.
> 

wait_iff_congested was broken once the block layer stopped tracking
congestion and became a glorified cond_resched() in most cases. This is
why the series aimed to remove the reliance on
congestion_wait/wait_iff_congested.

-- 
Mel Gorman
SUSE Labs