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Date:   Mon, 27 Jun 2022 23:12:58 +0800
From:   Feng Tang <feng.tang@intel.com>
To:     Shakeel Butt <shakeelb@google.com>
Cc:     Eric Dumazet <edumazet@google.com>, Linux MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        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>,
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Subject: Re: [net] 4890b686f4: netperf.Throughput_Mbps -69.4% regression
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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@intel.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