From: "T.J. Mercier" <tjmercier@google.com>
To: tjmercier@google.com, Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shakeel Butt <shakeelb@google.com>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
Efly Young <yangyifei03@kuaishou.com>
Cc: android-mm@google.com, yuzhao@google.com,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [PATCH] mm: memcg: Use larger chunks for proactive reclaim
Date: Wed, 31 Jan 2024 16:24:41 +0000 [thread overview]
Message-ID: <20240131162442.3487473-1-tjmercier@google.com> (raw)
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 in order to achieve fairness. After 0388536ac291 the number
of pages was limited to a maxmimum of 32 (SWAP_CLUSTER_MAX) to reduce
the amount of overreclaim. However such a small chunk size caused a
regression in reclaim performance due to many more reclaim start/stop
cycles inside memory_reclaim.
Instead of limiting reclaim chunk size to the SWAP_CLUSTER_MAX constant,
adjust the chunk size proportionally with number of pages left to
reclaim. This allows for higher reclaim efficiency with large chunk
sizes during the beginning of memory_reclaim, and reduces the amount of
potential overreclaim by using small chunk sizes as the total reclaim
amount is approached. Using 1/4 of the amount left to reclaim as the
chunk size gives a good compromise between reclaim performance and
overreclaim:
root - full reclaim pages/sec time (sec)
pre-0388536ac291 : 68047 10.46
post-0388536ac291 : 13742 inf
(reclaim-reclaimed)/4 : 67352 10.51
/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
/uid_0 - full reclaim pages/sec time (sec)
pre-0388536ac291 : 72334 7.09
post-0388536ac291 : 38105 14.45
(reclaim-reclaimed)/4 : 72914 6.96
Fixes: 0388536ac291 ("mm:vmscan: fix inaccurate reclaim during proactive reclaim")
Signed-off-by: T.J. Mercier <tjmercier@google.com>
---
mm/memcontrol.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 46d8d02114cf..d68fb89eadd2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6977,7 +6977,8 @@ static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf,
lru_add_drain_all();
reclaimed = try_to_free_mem_cgroup_pages(memcg,
- min(nr_to_reclaim - nr_reclaimed, SWAP_CLUSTER_MAX),
+ max((nr_to_reclaim - nr_reclaimed) / 4,
+ (nr_to_reclaim - nr_reclaimed) % 4),
GFP_KERNEL, reclaim_options);
if (!reclaimed && !nr_retries--)
--
2.43.0.594.gd9cf4e227d-goog
next reply other threads:[~2024-01-31 16:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-31 16:24 T.J. Mercier [this message]
2024-01-31 17:50 ` [PATCH] mm: memcg: Use larger chunks for proactive reclaim Johannes Weiner
2024-01-31 18:01 ` T.J. Mercier
2024-01-31 20:12 ` Johannes Weiner
2024-02-01 13:57 ` Michal Koutný
2024-02-01 15:34 ` Johannes Weiner
2024-02-01 18:10 ` T.J. Mercier
2024-02-02 5:02 ` Efly Young
2024-02-02 10:15 ` Michal Koutný
2024-02-02 18:22 ` T.J. Mercier
2024-02-02 19:46 ` Michal Koutný
2024-02-02 21:42 ` T.J. Mercier
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