From: Johannes Weiner <hannes@cmpxchg.org>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, david@kernel.org, mhocko@kernel.org,
zhengqi.arch@bytedance.com, shakeel.butt@linux.dev,
axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com,
ljs@kernel.org, baohua@kernel.org, kasong@tencent.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: vmscan: fix dirty folios throttling on cgroup v1 for MGLRU
Date: Fri, 27 Mar 2026 12:41:06 -0400 [thread overview]
Message-ID: <acazIi04wEGrKq14@cmpxchg.org> (raw)
In-Reply-To: <3445af0f09e8ca945492e052e82594f8c4f2e2f6.1774606060.git.baolin.wang@linux.alibaba.com>
On Fri, Mar 27, 2026 at 06:21:08PM +0800, Baolin Wang wrote:
> The balance_dirty_pages() won't do the dirty folios throttling on cgroupv1.
> See commit 9badce000e2c ("cgroup, writeback: don't enable cgroup writeback
> on traditional hierarchies").
>
> Moreover, after commit 6b0dfabb3555 ("fs: Remove aops->writepage"), we no
> longer attempt to write back filesystem folios through reclaim.
>
> On large memory systems, the flusher may not be able to write back quickly
> enough. Consequently, MGLRU will encounter many folios that are already
> under writeback. Since we cannot reclaim these dirty folios, the system
> may run out of memory and trigger the OOM killer.
>
> Hence, for cgroup v1, let's throttle reclaim after waking up the flusher,
> which is similar to commit 81a70c21d917 ("mm/cgroup/reclaim: fix dirty
> pages throttling on cgroup v1"), to avoid unnecessary OOM.
This fix for cgroup1 makes sense to me. For cgroup2, MGLRU shares the
shrink_node() reclaim throttling.
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
The remaining notable difference is global reclaim. I don't see any
equivalent throttling in the lru_gen_shrink_node() path. What prevents
premature OOMs at the system level?
next prev parent reply other threads:[~2026-03-27 16:41 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-27 10:21 [PATCH] mm: vmscan: fix dirty folios throttling on cgroup v1 for MGLRU Baolin Wang
2026-03-27 15:30 ` Andrew Morton
2026-03-28 2:38 ` Baolin Wang
2026-03-27 16:41 ` Johannes Weiner [this message]
2026-03-27 17:59 ` Kairui Song
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