Re: [net] 4890b686f4: netperf.Throughput_Mbps -69.4% regression

From: Shakeel Butt <shakeelb@google.com>
To: Feng Tang <feng.tang@intel.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>,
	"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
Date: Mon, 27 Jun 2022 09:25:20 -0700	[thread overview]
Message-ID: <CALvZod5fxjZSWp=ikxhKN+JRaoWA4_ErNaJg1fieci3LY+-7qg@mail.gmail.com> (raw)
In-Reply-To: <20220627151258.GB20878@shbuild999.sh.intel.com>

On Mon, Jun 27, 2022 at 8:25 AM Feng Tang <feng.tang@intel.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@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. 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