linux-kernel - Re: [PATCH 1/2] mm: vmscan: restore high-cpu watermark safety in kswapd

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Message-ID: <e754fdc5-de73-477e-a78d-b0fa9ce730f7@suse.cz>
Date: Wed, 16 Apr 2025 16:53:55 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Johannes Weiner <hannes@...xchg.org>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Brendan Jackman <jackmanb@...gle.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: vmscan: restore high-cpu watermark safety in
 kswapd

On 4/16/25 15:45, Johannes Weiner wrote:
> Vlastimil points out that commit a211c6550efc ("mm: page_alloc:
> defrag_mode kswapd/kcompactd watermarks") switched kswapd from
> zone_watermark_ok_safe() to the standard, percpu-cached version of
> reading free pages, thus dropping the watermark safety precautions for
> systems with high CPU counts (e.g. >212 cpus on 64G). Restore them.
> 
> Since zone_watermark_ok_safe() is no longer the right interface, and
> this was the last caller of the function anyway, open-code the
> zone_page_state_snapshot() conditional and delete the function.
> 
> Reported-by: Vlastimil Babka <vbabka@...e.cz>
> Fixes: a211c6550efc ("mm: page_alloc: defrag_mode kswapd/kcompactd watermarks")
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>