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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>
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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?