Re: [PATCH 3/3] memcg: increase MEMCG_CHARGE_BATCH to 64

[Roman Gushchin <roman.gushchin@linux.dev>]

On Mon, Aug 22, 2022 at 12:17:37AM +0000, Shakeel Butt wrote:
> 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%.

This is pretty significant!

Acked-by: Roman Gushchin <roman.gushchin@linux.dev>

I wonder only if we want to make it configurable (Idk a sysctl or maybe
a config option) and close the topic.

Thanks!