linux-kernel - Re: [LKP] [lkp] [sctp] a6c2f79287: netperf.Throughput

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Date:	Fri, 5 Aug 2016 11:31:09 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	Xin Long <lucien.xin@...il.com>
Cc:	kernel test robot <xiaolong.ye@...el.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>, lkp@...org,
	"David S. Miller" <davem@...emloft.net>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [LKP] [lkp] [sctp] a6c2f79287: netperf.Throughput_Mbps -37.2%
 regression

On Thu, Jul 28, 2016 at 03:01:36PM +0800, Xin Long wrote:
> On Wed, Jul 27, 2016 at 9:54 AM, kernel test robot
> <xiaolong.ye@...el.com> wrote:
> >
> > FYI, we noticed a -37.2% regression of netperf.Throughput_Mbps due to commit:
> >
> > commit a6c2f792873aff332a4689717c3cd6104f46684c ("sctp: implement prsctp TTL policy")
> > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> >
> > in testcase: netperf
> > on test machine: 4 threads Ivy Bridge with 8G memory
> > with following parameters:
> >
> >         ip: ipv4
> >         runtime: 300s
> >         nr_threads: 200%
> >         cluster: cs-localhost
> >         send_size: 10K
> >         test: SCTP_STREAM_MANY
> >         cpufreq_governor: performance
> >
> >
> >
> > Disclaimer:
> > Results have been estimated based on internal Intel analysis and are provided
> > for informational purposes only. Any difference in system hardware or software
> > design or configuration may affect actual performance.
> >
> It doesn't make much sense to me. the codes I added cannot be
> triggered without enable any pr policies. and I also did the tests in

It seems these pr policies has to be turned on by user space, i.e.
netperf in this case?

I checked netperf's source code, it doesn't seem set any option
related to SCTP PR POLICY but I'm new to network code so I could be
wrong or missing something.

> my local environment,  the result looks normal to me compare to
> prior version.

Can you share your number?
We run netperf like this:
netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1
The full log of the run is attached for your reference.

> 
> Recently the sctp performance is not stable,  as during these patches,
> netperf cannot get the result, but return ENOTCONN. which may
> also affect the testing. anyway we've fixed the -ENOTCONN issue
> already in the latest version.

I tested commit 96b585267f55, which is Linus' git tree HEAD on 08/03, I
guess the fix you mentioned should already be in there? But
unfortunately, the throughput of netperf is still at low number(we did
the test 5 times):
$ cat */netperf.json
{
  "netperf.Throughput_Mbps": [
    2470.6974999999998
  ]
}{
  "netperf.Throughput_Mbps": [
    2486.7675
  ]
}{
  "netperf.Throughput_Mbps": [
    2478.945
  ]
}{
  "netperf.Throughput_Mbps": [
    2429.465
  ]
}{
  "netperf.Throughput_Mbps": [
    2476.9150000000004
  ]

Considering what you have said that the patch shouldn't make a
difference, the performance drop is really confusing. Any idea what
could be the cause? Thanks.

Regards,
Aaron

View attachment "netperf" of type "text/plain" (4641 bytes)