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References: <20211202150614.22440-1-mgorman@techsingularity.net>
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From: Shakeel Butt <shakeelb@google.com>
Date: Sun, 5 Dec 2021 22:06:27 -0800
Message-ID: <CALvZod5BmFVdosG=e2NcEzeuzv0W9WifSBmeD48xnn1k+SNRKg@mail.gmail.com>
Subject: Re: [PATCH v4 1/1] mm: vmscan: Reduce throttling due to a failure to
 make progress
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrew Morton <akpm@linux-foundation.org>, Michal Hocko <mhocko@suse.com>, 
	Vlastimil Babka <vbabka@suse.cz>, Alexey Avramov <hakavlad@inbox.lv>, Rik van Riel <riel@surriel.com>, 
	Mike Galbraith <efault@gmx.de>, 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>
Content-Type: text/plain; charset="UTF-8"

On Fri, Dec 3, 2021 at 11:08 AM Mel Gorman <mgorman@techsingularity.net> wrote:
>
[...]
> > I am in agreement with the motivation of the whole series. I am just
> > making sure that the motivation of VMSCAN_THROTTLE_NOPROGRESS based
> > throttle is more than just the congestion_wait of
> > mem_cgroup_force_empty_write.
> >
>
> The commit that primarily targets congestion_wait is 8cd7c588decf
> ("mm/vmscan: throttle reclaim until some writeback completes if
> congested"). The series recognises that there are other reasons why
> reclaim can fail to make progress that is not directly writeback related.
>

I agree with throttling for VMSCAN_THROTTLE_[WRITEBACK|ISOLATED]
reasons. Please explain why we should throttle for
VMSCAN_THROTTLE_NOPROGRESS? Also 69392a403f49 claims "Direct reclaim
primarily is throttled in the page allocator if it is failing to make
progress.", can you please explain how?