From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============1624688071289347924==" MIME-Version: 1.0 From: Shakeel Butt To: lkp@lists.01.org Subject: [PATCH 3/3] memcg: increase MEMCG_CHARGE_BATCH to 64 Date: Mon, 22 Aug 2022 00:17:37 +0000 Message-ID: <20220822001737.4120417-4-shakeelb@google.com> In-Reply-To: <20220822001737.4120417-1-shakeelb@google.com> List-Id: --===============1624688071289347924== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable For several years, MEMCG_CHARGE_BATCH was kept at 32 but with bigger machines and the network intensive workloads requiring througput in Gbps, 32 is too small and makes the memcg charging path a bottleneck. For now, increase it to 64 for easy acceptance to 6.0. We will need to revisit this in future for ever increasing demand of higher performance. Please note that the memcg charge path drain the per-cpu memcg charge stock, so there should not be any oom behavior change. To evaluate the impact of this optimization, on a 72 CPUs machine, we ran the following workload in a three level of cgroup hierarchy with top level having min and low setup appropriately. More specifically memory.min equal to size of netperf binary and memory.low double of that. $ netserver -6 # 36 instances of netperf with following params $ netperf -6 -H ::1 -l 60 -t TCP_SENDFILE -- -m 10K Results (average throughput of netperf): Without (6.0-rc1) 10482.7 Mbps With patch 17064.7 Mbps (62.7% improvement) With the patch, the throughput improved by 62.7%. Signed-off-by: Shakeel Butt Reported-by: kernel test robot --- include/linux/memcontrol.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 4d31ce55b1c0..70ae91188e16 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -354,10 +354,11 @@ struct mem_cgroup { }; = /* - * size of first charge trial. "32" comes from vmscan.c's magic value. - * TODO: maybe necessary to use big numbers in big irons. + * size of first charge trial. + * TODO: maybe necessary to use big numbers in big irons or dynamic based = of the + * workload. */ -#define MEMCG_CHARGE_BATCH 32U +#define MEMCG_CHARGE_BATCH 64U = extern struct mem_cgroup *root_mem_cgroup; = -- = 2.37.1.595.g718a3a8f04-goog --===============1624688071289347924==--