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From: Andrew Morton <akpm@linux-foundation.org>
To: Wupeng Ma <mawupeng1@huawei.com>
Cc: <liuye@kylinos.cn>, <hannes@cmpxchg.org>, <mhocko@kernel.org>,
	<david@kernel.org>, <ljs@kernel.org>, <hughd@google.com>,
	<mgorman@techsingularity.net>, <yang@os.amperecomputing.com>,
	<zhangqiuhao@huawei.com>, <wangkefeng.wang@huawei.com>,
	<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/2] mm: vmscan: fix scan overshoot and ineligible folio scanning
Date: Tue, 11 Aug 2026 18:42:41 -0700	[thread overview]
Message-ID: <20260811184241.e423b81c8a50d5f212af1c3b@linux-foundation.org> (raw)
In-Reply-To: <20260811070849.1332165-1-mawupeng1@huawei.com>

On Tue, 11 Aug 2026 15:08:47 +0800 Wupeng Ma <mawupeng1@huawei.com> wrote:

> shrink_lruvec() drives reclaim in SWAP_CLUSTER_MAX (32) chunks, but
> isolate_lru_folios() may scan far more than that per call on a single
> LRU.  The excess is never charged back, so shrink_lruvec() keeps
> rescanning the same folios round after round.  When reclaim targets a
> lower zone, the same scanner also keeps walking zone-ineligible folios
> that can never satisfy the allocation, inflating nr_reclaimed into a
> false progress that delays the OOM.
> 
> This series fixes both:
> 
>   [1/2] Charge the isolate overshoot against the scan quota so the
>         next round skips already-scanned folios.
>   [2/2] Stop scanning once too many zone-ineligible folios have been
>         skipped, instead of force-isolating them.

This all sounds fairly bad.  Is there some report?  Real-world test
results?  Laboratory test results?  Something to help us understand the
impact of the issues and the situations in which they occur.

Thanks.

  parent reply	other threads:[~2026-08-12  1:42 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-11  7:08 Wupeng Ma
2026-08-11  7:08 ` [PATCH 1/2] mm: vmscan: charge isolate overshoot against scan quota Wupeng Ma
2026-08-11  7:08 ` [PATCH 2/2] mm: vmscan: stop scanning ineligible folios after max_nr_skipped Wupeng Ma
2026-08-12  1:42 ` Andrew Morton [this message]
2026-08-12  2:29   ` [PATCH 0/2] mm: vmscan: fix scan overshoot and ineligible folio scanning mawupeng
2026-08-25  0:59     ` mawupeng
2026-08-30  3:18       ` Andrew Morton

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