linux-kernel - [REGRESSION][BISECTED] Unexpected OOM instead of reclaiming inactive file pages

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Message-ID: <5905724.LvFx2qVVIh@natalenko.name>
Date: Mon, 11 Aug 2025 17:48:08 +0200
From: Oleksandr Natalenko <oleksandr@...alenko.name>
To: linux-kernel@...r.kernel.org
Cc: linux-block@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
 Damien Le Moal <dlemoal@...nel.org>, John Garry <john.g.garry@...cle.com>,
 Christoph Hellwig <hch@....de>,
 "Martin K. Petersen" <martin.petersen@...cle.com>, linux-mm@...ck.org,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Shakeel Butt <shakeel.butt@...ux.dev>, Qi Zheng <zhengqi.arch@...edance.com>,
 Michal Hocko <mhocko@...nel.org>, David Hildenbrand <david@...hat.com>,
 Johannes Weiner <hannes@...xchg.org>,
 Andrew Morton <akpm@...ux-foundation.org>
Subject:
 [REGRESSION][BISECTED] Unexpected OOM instead of reclaiming inactive file
 pages

Hello Damien.

I'm fairly confident that the following commit

459779d04ae8d block: Improve read ahead size for rotational devices

caused a regression in my test bench.

I'm running v6.17-rc1 in a small QEMU VM with virtio-scsi disk. It has got 1 GiB of RAM, so I can saturate it easily causing reclaiming mechanism to kick in.

If MGLRU is enabled:

$ echo 1000 | sudo tee /sys/kernel/mm/lru_gen/min_ttl_ms

then, once page cache builds up, an OOM happens without reclaiming inactive file pages: [1]. Note that inactive_file:506952kB, I'd expect these to be reclaimed instead, like how it happens with v6.16.

If MGLRU is disabled:

$ echo 0 | sudo tee /sys/kernel/mm/lru_gen/min_ttl_ms

then OOM doesn't occur, and things seem to work as usual.

If MGLRU is enabled, and 459779d04ae8d is reverted on top of v6.17-rc1, the OOM doesn't happen either.

Could you please check this?

Thank you.

-- 
Oleksandr Natalenko, MSE

[1]: https://paste.voidband.net/TG5OiZ29.log
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