Commit 1813e51e authored by Shakeel Butt's avatar Shakeel Butt Committed by Andrew Morton

memcg: increase MEMCG_CHARGE_BATCH to 64

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.  Though it does
have impact on rstat flushing and high limit reclaim backoff.

To evaluate the impact of this optimization, on a 72 CPUs machine, we
ran the following workload in a three level of cgroup hierarchy.

 $ 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%.

Link: https://lkml.kernel.org/r/20220825000506.239406-4-shakeelb@google.comSigned-off-by: default avatarShakeel Butt <shakeelb@google.com>
Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
Acked-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: default avatarFeng Tang <feng.tang@intel.com>
Acked-by: default avatarRoman Gushchin <roman.gushchin@linux.dev>
Acked-by: default avatarMuchun Song <songmuchun@bytedance.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Michal Koutný" <mkoutny@suse.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 408587ba
...@@ -354,10 +354,11 @@ struct mem_cgroup { ...@@ -354,10 +354,11 @@ struct mem_cgroup {
}; };
/* /*
* size of first charge trial. "32" comes from vmscan.c's magic value. * size of first charge trial.
* TODO: maybe necessary to use big numbers in big irons. * 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; extern struct mem_cgroup *root_mem_cgroup;
......
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