Date:   Wed, 1 Dec 2021 15:06:13 +0000
From:   Mel Gorman <mgorman@techsingularity.net>
To:     Mike Galbraith <efault@gmx.de>
Cc:     Alexey Avramov <hakavlad@inbox.lv>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Rik van Riel <riel@surriel.com>,
        Darrick Wong <djwong@kernel.org>, regressions@lists.linux.dev,
        Linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1] mm: vmscan: Reduce throttling due to a failure to
 make progress
Message-ID: <20211201150613.GV3366@techsingularity.net>
References: <20211125151853.8540-1-mgorman@techsingularity.net>
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 <20211129150117.GO3366@techsingularity.net>
 <20211201010348.31e99637@mail.inbox.lv>
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 <c2aee7e6b9096556aab9b47156e91082c9345a90.camel@gmx.de>
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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