linux-kernel - Re: [PATCH 1/2] mm/mglru: only clear kswapd

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Message-Id: <20241014162541.a3049d0824a2f9b22221c17a@linux-foundation.org>
Date: Mon, 14 Oct 2024 16:25:41 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Wei Xu <weixugc@...gle.com>
Cc: Yu Zhao <yuzhao@...gle.com>, Axel Rasmussen <axelrasmussen@...gle.com>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm/mglru: only clear kswapd_failures if reclaimable

On Mon, 14 Oct 2024 22:12:11 +0000 Wei Xu <weixugc@...gle.com> wrote:

> lru_gen_shrink_node() unconditionally clears kswapd_failures, which
> can prevent kswapd from sleeping and cause 100% kswapd cpu usage even
> when kswapd repeatedly fails to make progress in reclaim.
> 
> Only clear kswap_failures in lru_gen_shrink_node() if reclaim makes
> some progress, similar to shrink_node().

That sounds bad.  What triggers this?  Can you suggest why it has just
bee discovered, after 1.5 years?  And should the fix be backported into
-stable kernels?