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

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Date:	Wed, 17 Aug 2016 13:04:29 +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 08/16/2016 05:56 PM, Xin Long wrote:
>>>>
>>>> I'm testing on Linus' master, can we all use that please?
>>>>
>>>
>>> [git] git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>>>
>>> [mechine]
>>> Intel(R) Xeon(R) CPU E5-2690 v2 @ 3.00GHz
>>> mem 62G (66000220K)
>>>
>>> [system]
>>> # cat /etc/redhat-release
>>> Red Hat Enterprise Linux Server release 7.3 Beta (Maipo)
>>>
>>> [commit 3684b03]
>>> [root@...dl380pg8-11 lxin]# uname -r
>>> 4.8.0-rc2.3684b03
>>> [root@...dl380pg8-11 lxin]# cat test.sh
>>> killall -0 netserver || netserver -4 &
>>> netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1
>>
>> I just realized the test we are doing is not exactly the same.
>> As the original report says:
>>         ip: ipv4
>>         runtime: 300s
>>         nr_threads: 200%
>>         cluster: cs-localhost
>>         send_size: 10K
>>         test: SCTP_STREAM_MANY
>>         cpufreq_governor: performance
>>
>> Note the nr_threads: 200%, which means to start 2 times of CPU number
>> processes of netperf.
>>
>> In our IVB i3(2 cores, 2 threads per core) case, 8 netperf processes
>> are started concurrently:
> OK, understand.
> 
>>
>> 2016-07-27 03:48:09 netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1 &
>> 2016-07-27 03:48:09 netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1 &
>> 2016-07-27 03:48:09 netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1 &
>> 2016-07-27 03:48:09 netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1 &
>> 2016-07-27 03:48:09 netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1 &
>> 2016-07-27 03:48:09 netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1 &
>> 2016-07-27 03:48:09 netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1 &
>> 2016-07-27 03:48:09 netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1 &
>>
>> The throughput is the average of those runs.
>>
>> And I think we should be doing test on:
>> commit a6c2f79287 ("sctp: implement prsctp TTL policy") (the bisected one)
>> and
>> commit 826d253d57 ("sctp: add SCTP_PR_ASSOC_STATUS on sctp sockopt") (its immediate parent)
>> instead of Linus' master HEAD to avoid other factors.
>>
> OK, I will do tests as your suggestion now,  but need to rebuild again :D
> 
> can you disable pr_enable with "sysctl -w net.sctp.prsctp_enable=0",
> then try again?

For commit a6c2f79287 ("sctp: implement prsctp TTL policy"), no matter
the value of net.sctp.prsctp_enable, the throughput is almost the same:

net.sctp.prsctp_enable = 0
{
  "netperf.Throughput_Mbps": [
    2353.3112499999997
  ]
}

net.sctp.prsctp_enable = 1
{
  "netperf.Throughput_Mbps": [
    2371.5862500000003
  ]
}

For its immediate parent:
commit 826d253d57 ("sctp: add SCTP_PR_ASSOC_STATUS on sctp sockopt")
No matter the value of net.sctp.prsctp_enable, the throughput is again
almost the same:

net.sctp.prsctp_enable = 0
{
  "netperf.Throughput_Mbps": [
    3838.8300000000004
  ]
}

net.sctp.prsctp_enable = 1
{
  "netperf.Throughput_Mbps": [
    3751.4600000000005
  ]
}

Does this result give any hint?

Thanks,
Aaron