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

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Message-ID: <20161009074142.GA9546@aaronlu.sh.intel.com>
Date:   Sun, 9 Oct 2016 15:41:42 +0800
From:   Aaron Lu <aaron.lu@...el.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        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>,
        "Chen, Tim C" <tim.c.chen@...el.com>,
        Huang Ying <ying.huang@...el.com>
Subject: Re: [LKP] [lkp] [sctp] a6c2f79287: netperf.Throughput_Mbps -37.2%
 regression

On Mon, Oct 03, 2016 at 10:32:04AM +0800, Xin Long wrote:
> On Fri, Sep 30, 2016 at 3:05 PM, Aaron Lu <aaron.lu@...el.com> wrote:
> > On 08/23/2016 05:44 AM, Marcelo Ricardo Leitner wrote:
> >> Em 19-08-2016 04:24, Aaron Lu escreveu:
> >>> On Fri, Aug 19, 2016 at 04:19:39AM -0300, Marcelo Ricardo Leitner wrote:
> >>>> Hi,
> >>>>
> >>>> Em 19-08-2016 02:29, Aaron Lu escreveu:
> >>>> ...
> >>>>> It doesn't look insane and sctp_wait_for_sndbuf may actually have
> >>>>> something to do with a larger sctp_chunk I suppose?
> >>>>>
> >>>>> The same perf record doesn't capture any sample for the good commit,
> >>>>> which suggests the nerperf process doesn't sleep in sctp_wait_for_sndbuf.
> >>>>
> >>>> Ahhh yes! It does, and then it would mean your txbuf is too small for the
> >>>> chunk sizes you're using (sctp tests option -m).
> >>>>
> >>>> What's your netperf cmdline again please?
> >>>
> >>> netperf -4 -t SCTP_STREAM_MANY -c -C -l 300 -- -m 10K -H 127.0.0.1
> >>>
> >>> Is the 10K used here a problem? If so, can you suggest a proper value
> >>> for our netperf performance test? Thanks.
> >>
> >> We're still working on this. Xin could reproduce it on an i3 too, but
> >> I'm afraid this commit just unmasked an issue in there. You're
> >> overloading the CPU by too much when spawning 8 parallel netperf's on a
> >> 4-core system, seems that commit a6c2f79287 was that last rock that made
> >> it slip into a precipice. sctp's cwnd and rwnd management are not as
> >> good as tcp's and now it seems you're triggering a corner case.
> >>
> >> I hope to have more soon.
> >
> > I wonder if there is any update on this issue?
> >
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> 
> be4947b sctp: change to check peer prsctp_capable when using prsctp polices
> 0605483 sctp: remove prsctp_param from sctp_chunk
> 73dca12 sctp: move sent_count to the memory hole in sctp_chunk
> 
> These three commit can avoid this issue by recovering sctp_chunk size.

Thanks for the update, I just confirmed the throughput is back on my
desktop.