The quilt patch titled
Subject: mm: memcg: use larger batches for proactive reclaim
has been removed from the -mm tree. Its filename was
mm-memcg-use-larger-batches-for-proactive-reclaim.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: "T.J. Mercier" <tjmercier@xxxxxxxxxx>
Subject: mm: memcg: use larger batches for proactive reclaim
Date: Fri, 2 Feb 2024 23:38:54 +0000
Before 388536ac291 ("mm:vmscan: fix inaccurate reclaim during proactive
reclaim") we passed the number of pages for the reclaim request directly
to try_to_free_mem_cgroup_pages, which could lead to significant
overreclaim. After 0388536ac291 the number of pages was limited to a
maximum 32 (SWAP_CLUSTER_MAX) to reduce the amount of overreclaim.
However such a small batch size caused a regression in reclaim performance
due to many more reclaim start/stop cycles inside memory_reclaim. The
restart cost is amortized over more pages with larger batch sizes, and
becomes a significant component of the runtime if the batch size is too
small.
Reclaim tries to balance nr_to_reclaim fidelity with fairness across nodes
and cgroups over which the pages are spread. As such, the bigger the
request, the bigger the absolute overreclaim error. Historic in-kernel
users of reclaim have used fixed, small sized requests to approach an
appropriate reclaim rate over time. When we reclaim a user request of
arbitrary size, use decaying batch sizes to manage error while maintaining
reasonable throughput.
MGLRU enabled - memcg LRU used
root - full reclaim pages/sec time (sec)
pre-0388536ac291 : 68047 10.46
post-0388536ac291 : 13742 inf
(reclaim-reclaimed)/4 : 67352 10.51
MGLRU enabled - memcg LRU not used
/uid_0 - 1G reclaim pages/sec time (sec) overreclaim (MiB)
pre-0388536ac291 : 258822 1.12 107.8
post-0388536ac291 : 105174 2.49 3.5
(reclaim-reclaimed)/4 : 233396 1.12 -7.4
MGLRU enabled - memcg LRU not used
/uid_0 - full reclaim pages/sec time (sec)
pre-0388536ac291 : 72334 7.09
post-0388536ac291 : 38105 14.45
(reclaim-reclaimed)/4 : 72914 6.96
[tjmercier@xxxxxxxxxx: v4]
Link: https://lkml.kernel.org/r/20240206175251.3364296-1-tjmercier@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20240202233855.1236422-1-tjmercier@xxxxxxxxxx
Fixes: 0388536ac291 ("mm:vmscan: fix inaccurate reclaim during proactive reclaim")
Signed-off-by: T.J. Mercier <tjmercier@xxxxxxxxxx>
Reviewed-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Michal Koutny <mkoutny@xxxxxxxx>
Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Efly Young <yangyifei03@xxxxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/mm/memcontrol.c~mm-memcg-use-larger-batches-for-proactive-reclaim
+++ a/mm/memcontrol.c
@@ -6981,6 +6981,8 @@ static ssize_t memory_reclaim(struct ker
reclaim_options = MEMCG_RECLAIM_MAY_SWAP | MEMCG_RECLAIM_PROACTIVE;
while (nr_reclaimed < nr_to_reclaim) {
+ /* Will converge on zero, but reclaim enforces a minimum */
+ unsigned long batch_size = (nr_to_reclaim - nr_reclaimed) / 4;
unsigned long reclaimed;
if (signal_pending(current))
@@ -6995,8 +6997,7 @@ static ssize_t memory_reclaim(struct ker
lru_add_drain_all();
reclaimed = try_to_free_mem_cgroup_pages(memcg,
- min(nr_to_reclaim - nr_reclaimed, SWAP_CLUSTER_MAX),
- GFP_KERNEL, reclaim_options);
+ batch_size, GFP_KERNEL, reclaim_options);
if (!reclaimed && !nr_retries--)
return -EAGAIN;
_
Patches currently in -mm which might be from tjmercier@xxxxxxxxxx are
