Re: [PATCH v2 3/3] memcg: increase MEMCG_CHARGE_BATCH to 64

From: Muchun Song <muchun.song@linux.dev>
To: Shakeel Butt <shakeelb@google.com>
Cc: "Johannes Weiner" <hannes@cmpxchg.org>,
	"Michal Hocko" <mhocko@kernel.org>,
	"Roman Gushchin" <roman.gushchin@linux.dev>,
	"Muchun Song" <songmuchun@bytedance.com>,
	"Michal Koutný" <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" <linux-mm@kvack.org>, netdev <netdev@vger.kernel.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/3] memcg: increase MEMCG_CHARGE_BATCH to 64
Date: Thu, 25 Aug 2022 16:30:48 +0800	[thread overview]
Message-ID: <4A0F7B38-2701-486D-A847-DCC4B49F8EAF@linux.dev> (raw)
In-Reply-To: <20220825000506.239406-4-shakeelb@google.com>

> On Aug 25, 2022, at 08:05, Shakeel Butt <shakeelb@google.com> 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. 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%.

This is very impressive.

> 
> Signed-off-by: Shakeel Butt <shakeelb@google.com>
> Reported-by: kernel test robot <oliver.sang@intel.com>
> Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
> Reviewed-by: Feng Tang <feng.tang@intel.com>
> Acked-by: Roman Gushchin <roman.gushchin@linux.dev>

Acked-by: Muchun Song <songmuchun@bytedance.com>

Thanks.