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Date:   Mon, 22 Aug 2022 11:37:30 -0700
From:   Roman Gushchin <roman.gushchin@linux.dev>
To:     Shakeel Butt <shakeelb@google.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Muchun Song <songmuchun@bytedance.com>,
        Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>,
        Eric Dumazet <edumazet@google.com>,
        Soheil Hassas Yeganeh <soheil@google.com>,
        Feng Tang <feng.tang@intel.com>,
        Oliver Sang <oliver.sang@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>, lkp@lists.01.org,
        cgroups@vger.kernel.org, linux-mm@kvack.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] memcg: increase MEMCG_CHARGE_BATCH to 64
Message-ID: <YwPM6o1+pZ2kRyy3@P9FQF9L96D>
References: <20220822001737.4120417-1-shakeelb@google.com>
 <20220822001737.4120417-4-shakeelb@google.com>
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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!