Re: [PATCH] mm/cgroup/reclaim: Fix dirty pages throttling on cgroup v1

[Johannes Weiner <hannes@cmpxchg.org>]

On Fri, Nov 18, 2022 at 12:36:03PM +0530, Aneesh Kumar K.V wrote:
> balance_dirty_pages doesn't do the required dirty throttling on cgroupv1. See
> commit 9badce000e2c ("cgroup, writeback: don't enable cgroup writeback on
> traditional hierarchies"). Instead, the kernel depends on writeback throttling
> in shrink_folio_list to achieve the same goal. With large memory systems, the
> flusher may not be able to writeback quickly enough such that we will start
> finding pages in the shrink_folio_list already in writeback. Hence for cgroupv1
> let's do a reclaim throttle after waking up the flusher.
> 
> The below test which used to fail on a 256GB system completes till the
> the file system is full with this change.
> 
> root@lp2:/sys/fs/cgroup/memory# mkdir test
> root@lp2:/sys/fs/cgroup/memory# cd test/
> root@lp2:/sys/fs/cgroup/memory/test# echo 120M > memory.limit_in_bytes
> root@lp2:/sys/fs/cgroup/memory/test# echo $$ > tasks
> root@lp2:/sys/fs/cgroup/memory/test# dd if=/dev/zero of=/home/kvaneesh/test bs=1M
> Killed
> 
> Cc: <stable@kernel.org>
> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Thanks Aneesh