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

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Date:	Wed, 17 Aug 2016 02:34:46 +0800
From:	Xin Long <lucien.xin@...il.com>
To:	Aaron Lu <aaron.lu@...el.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

>
> 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.
>
The test result shows they are almost same:

826d253d57
=========================
[root@...alhost lxin]# sysctl -w net.sctp.prsctp_enable=1
net.sctp.prsctp_enable = 1
15484.93
15557.69
15395.61

[root@...alhost lxin]# sysctl -w net.sctp.prsctp_enable=0
net.sctp.prsctp_enable = 0
15369.83
14419.81
15202.59


a6c2f79287
===========
[root@...alhost lxin]# sysctl -w net.sctp.prsctp_enable=1
net.sctp.prsctp_enable = 1
15198.00
15567.87
16092.55

[root@...alhost lxin]# sysctl -w net.sctp.prsctp_enable=0
net.sctp.prsctp_enable = 0
15624.70
15021.85
15390.62

You can also review the commit a6c2f79287 if you have time:

It just added some 'if()' in the sending path if we don't use
any policy . In our test, no policy was used, I even added
log in kernel to check if some unexpected policy is enabled.

But still no.

If you can reproduce this issue stably, I suggest you can reverse
some code of that patch (it's a really a small patch)  and re-build
the kernel, then try.
With that, you can locate which line exactly triggered this issue.

Thanks.