Re: [PATCH] mm/vmscan: wake up flushers conditionally to avoid cgroup OOM

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 29 Aug 2024 18:25:43 +0800 Jingxiang Zeng <jingxiangzeng.cas@gmail.com> wrote:

> From: Zeng Jingxiang <linuszeng@tencent.com>
> 
> Commit 14aa8b2d5c2e ("mm/mglru: don't sync disk for each aging cycle")
> removed the opportunity to wake up flushers during the MGLRU page
> reclamation process can lead to an increased likelihood of triggering
> OOM when encountering many dirty pages during reclamation on MGLRU.
> 
> This leads to premature OOM if there are too many dirty pages in cgroup:
> Killed
> 
> ...
>
> The flusher wake up was removed to decrease SSD wearing, but if we are 
> seeing all dirty folios at the tail of an LRU, not waking up the flusher 
> could lead to thrashing easily. So wake it up when a mem cgroups is 
> about to OOM due to dirty caches.

Thanks, I'll queue this for testing and review.  Could people please
consider whether we should backport this into -stable kernels.

> MGLRU still suffers OOM issue on latest mm tree, so the test is done
> with another fix merged [1].
> 
> Link: https://lore.kernel.org/linux-mm/CAOUHufYi9h0kz5uW3LHHS3ZrVwEq-kKp8S6N-MZUmErNAXoXmw@mail.gmail.com/ [1]

This one is already queued for -stable.