Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 27 Jun 2022 18:46:44 -0700
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, MPTCP Upstream <mptcp@lists.linux.dev>,
        "linux-sctp @ vger . kernel . org" <linux-sctp@vger.kernel.org>,
        lkp@lists.01.org, kbuild test robot <lkp@intel.com>,
        Huang Ying <ying.huang@intel.com>,
        Xing Zhengjun <zhengjun.xing@linux.intel.com>,
        Yin Fengwei <fengwei.yin@intel.com>, Ying Xu <yinxu@redhat.com>
Subject: Re: [net] 4890b686f4: netperf.Throughput_Mbps -69.4% regression
Message-ID: <YrpdhDx3DDXtxx7b@castle>
References: <20220624070656.GE79500@shbuild999.sh.intel.com>
 <20220624144358.lqt2ffjdry6p5u4d@google.com>
 <20220625023642.GA40868@shbuild999.sh.intel.com>
 <20220627023812.GA29314@shbuild999.sh.intel.com>
 <CANn89i+6NPujMyiQxriZRt6vhv6hNrAntXxi1uOhJ0SSqnJ47w@mail.gmail.com>
 <20220627123415.GA32052@shbuild999.sh.intel.com>
 <CANn89iJAoYCebNbXpNMXRoDUkFMhg9QagetVU9NZUq+GnLMgqQ@mail.gmail.com>
 <20220627144822.GA20878@shbuild999.sh.intel.com>
 <CANn89iLSWm-c4XE79rUsxzOp3VwXVDhOEPTQnWgeQ48UwM=u7Q@mail.gmail.com>
 <CALvZod60OHC4iQnyBd16evCHXa_8ucpHiRnm9iNErQeUOycGZw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALvZod60OHC4iQnyBd16evCHXa_8ucpHiRnm9iNErQeUOycGZw@mail.gmail.com>
Precedence: bulk

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.