netdev - Re: [net] 4890b686f4: netperf.Throughput

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Date:   Mon, 27 Jun 2022 09:25:20 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Feng Tang <feng.tang@...el.com>
Cc:     Eric Dumazet <edumazet@...gle.com>, Linux MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Muchun Song <songmuchun@...edance.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Xin Long <lucien.xin@...il.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        kernel test robot <oliver.sang@...el.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        network dev <netdev@...r.kernel.org>,
        linux-s390@...r.kernel.org, MPTCP Upstream <mptcp@...ts.linux.dev>,
        "linux-sctp @ vger . kernel . org" <linux-sctp@...r.kernel.org>,
        lkp@...ts.01.org, kbuild test robot <lkp@...el.com>,
        Huang Ying <ying.huang@...el.com>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>,
        Yin Fengwei <fengwei.yin@...el.com>, Ying Xu <yinxu@...hat.com>
Subject: Re: [net] 4890b686f4: netperf.Throughput_Mbps -69.4% regression

On Mon, Jun 27, 2022 at 8:25 AM Feng Tang <feng.tang@...el.com> wrote:
>
> On Mon, Jun 27, 2022 at 07:52:55AM -0700, Shakeel Butt wrote:
> > On Mon, Jun 27, 2022 at 5:34 AM Feng Tang <feng.tang@...el.com> wrote:
> > > Yes, 1% is just around noise level for a microbenchmark.
> > >
> > > I went check the original test data of Oliver's report, the tests was
> > > run 6 rounds and the performance data is pretty stable (0Day's report
> > > will show any std deviation bigger than 2%)
> > >
> > > The test platform is a 4 sockets 72C/144T machine, and I run the
> > > same job (nr_tasks = 25% * nr_cpus) on one CascadeLake AP (4 nodes)
> > > and one Icelake 2 sockets platform, and saw 75% and 53% regresson on
> > > them.
> > >
> > > In the first email, there is a file named 'reproduce', it shows the
> > > basic test process:
> > >
> > > "
> > >   use 'performane' cpufre  governor for all CPUs
> > >
> > >   netserver -4 -D
> > >   modprobe sctp
> > >   netperf -4 -H 127.0.0.1 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K  &
> > >   netperf -4 -H 127.0.0.1 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K  &
> > >   netperf -4 -H 127.0.0.1 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K  &
> > >   (repeat 36 times in total)
> > >   ...
> > >
> > > "
> > >
> > > Which starts 36 (25% of nr_cpus) netperf clients. And the clients number
> > > also matters, I tried to increase the client number from 36 to 72(50%),
> > > and the regression is changed from 69.4% to 73.7%
> > >
> >
> > Am I understanding correctly that this 69.4% (or 73.7%) regression is
> > with cgroup v2?
>
> Yes.
>
> > Eric did the experiments on v2 but on real hardware where the
> > performance impact was negligible.
> >
> > BTW do you see similar regression for tcp as well or just sctp?
>
> Yes, I run TCP_SENDFILE case with 'send_size'==10K, it hits a
> 70%+ regressioin.
>

Thanks Feng. I think we should start with squeezing whatever we can
from layout changes and then try other approaches like increasing
batch size or something else. I can take a stab at this next week.

thanks,
Shakeel