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Date: Mon, 27 Jun 2022 18:46:44 -0700
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From: Roman Gushchin <roman.gushchin@linux.dev>
To: Shakeel Butt <shakeelb@google.com>
Cc: Eric Dumazet <edumazet@google.com>, Feng Tang <feng.tang@intel.com>,
	Linux MM <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Muchun Song <songmuchun@bytedance.com>,
	Jakub Kicinski <kuba@kernel.org>, Xin Long <lucien.xin@gmail.com>,
	Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
	kernel test robot <oliver.sang@intel.com>,
	Soheil Hassas Yeganeh <soheil@google.com>,
	LKML <linux-kernel@vger.kernel.org>,
	network dev <netdev@vger.kernel.org>, linux-s390@vger.kernel.org,
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	Huang Ying <ying.huang@intel.com>,
	Xing Zhengjun <zhengjun.xing@linux.intel.com>,
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Subject: Re: [net] 4890b686f4: netperf.Throughput_Mbps -69.4% regression
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On Mon, Jun 27, 2022 at 09:48:01AM -0700, Shakeel Butt wrote:
> On Mon, Jun 27, 2022 at 9:26 AM Eric Dumazet <edumazet@google.com> wrote:
> >
> [...]
> > >
> >
> > I simply did the following and got much better results.
> >
> > But I am not sure if updates to ->usage are really needed that often...
> 
> I suspect we need to improve the per-cpu memcg stock usage here. Were
> the updates mostly from uncharge path or charge path or that's
> irrelevant?
> 
> I think doing full drain (i.e. drain_stock()) within __refill_stock()
> when the local cache is larger than MEMCG_CHARGE_BATCH is not best.
> Rather we should always keep at least MEMCG_CHARGE_BATCH for such
> scenarios.

+1, really good point.