Re: [LKP] [lkp] [sctp] a6c2f79287: netperf.Throughput_Mbps -37.2% regression

[Aaron Lu]

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.

OK, I see.

> 
> I hope to have more soon.

Looking forward to test your patches.
Thanks for the update.

Regards,
Aaron