linux-kernel - Re: [RESEND][PATCH v4] mm/vmscan: wake up flushers conditionally to avoid cgroup OOM

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Message-Id: <20241007191534.ceb663de5ac7ee3695a162a2@linux-foundation.org>
Date: Mon, 7 Oct 2024 19:15:34 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jingxiang Zeng <jingxiangzeng.cas@...il.com>
Cc: linux-mm@...ck.org, kasong@...cent.com, linuszeng@...cent.com,
 linux-kernel@...r.kernel.org, tjmercier@...gle.com, weixugc@...gle.com,
 yuzhao@...gle.com, chrisl@...nel.org
Subject: Re: [RESEND][PATCH v4] mm/vmscan: wake up flushers conditionally to
 avoid cgroup  OOM

On Tue,  8 Oct 2024 09:56:35 +0800 Jingxiang Zeng <jingxiangzeng.cas@...il.com> wrote:

> From: Jingxiang Zeng <linuszeng@...cent.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:
> 
> ...
> 
> 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 for persisting.

This patch has a somewhat difficult past and not a lot of review. 
I'll await feedback from other MGLRU developers before proceeding.