This is a note to let you know that I've just added the patch titled
mm/cgroup/reclaim: fix dirty pages throttling on cgroup v1
to the 6.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-cgroup-reclaim-fix-dirty-pages-throttling-on-cgroup-v1.patch
and it can be found in the queue-6.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 81a70c21d9170de67a45843bdd627f4cce9c4215 Mon Sep 17 00:00:00 2001
From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Date: Fri, 18 Nov 2022 12:36:03 +0530
Subject: mm/cgroup/reclaim: fix dirty pages throttling on cgroup v1
From: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
commit 81a70c21d9170de67a45843bdd627f4cce9c4215 upstream.
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
Link: https://lkml.kernel.org/r/20221118070603.84081-1-aneesh.kumar@xxxxxxxxxxxxx
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: zefan li <lizefan.x@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2472,8 +2472,20 @@ shrink_inactive_list(unsigned long nr_to
* the flushers simply cannot keep up with the allocation
* rate. Nudge the flusher threads in case they are asleep.
*/
- if (stat.nr_unqueued_dirty == nr_taken)
+ if (stat.nr_unqueued_dirty == nr_taken) {
wakeup_flusher_threads(WB_REASON_VMSCAN);
+ /*
+ * For cgroupv1 dirty throttling is achieved by waking up
+ * the kernel flusher here and later waiting on folios
+ * which are in writeback to finish (see shrink_folio_list()).
+ *
+ * Flusher may not be able to issue writeback quickly
+ * enough for cgroupv1 writeback throttling to work
+ * on a large system.
+ */
+ if (!writeback_throttling_sane(sc))
+ reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
+ }
sc->nr.dirty += stat.nr_dirty;
sc->nr.congested += stat.nr_congested;
Patches currently in stable-queue which might be from aneesh.kumar@xxxxxxxxxxxxx are
queue-6.0/mm-cgroup-reclaim-fix-dirty-pages-throttling-on-cgroup-v1.patch
