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

[Baolin Wang]

On 3/27/26 5:45 PM, Kairui Song wrote:
> 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>

Thanks.