Re: [RFC PATCH] mm: vmscan: fix dirty folios throttling on cgroup v1 for MGLRU

[Kairui Song]

On Wed, Mar 25, 2026 at 8:06 PM Baolin Wang
<baolin.wang@xxxxxxxxxxxxxxxxx> 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.
>
> The following test program can easily reproduce the OOM issue. With this patch
> applied, the test passes successfully.
>
> $mkdir /sys/fs/cgroup/memory/test
> $echo 256M > /sys/fs/cgroup/memory/test/memory.limit_in_bytes
> $echo $$ > /sys/fs/cgroup/memory/test/cgroup.procs
> $dd if=/dev/zero of=/mnt/data.bin bs=1M count=800
>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>

I've been testing and based a few patches based on this and it looks
good enough as a bug fix:

Reviewed-by: Kairui Song <kasong@xxxxxxxxxxx>