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Subject: Re: [LKP] [lkp] [sctp] a6c2f79287: netperf.Throughput_Mbps -37.2%
 regression
To: Xin Long <lucien.xin@gmail.com>
References: <20160805033109.GA28539@aaronlu.sh.intel.com>
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Cc: kernel test robot <xiaolong.ye@intel.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>, lkp@01.org,
        "David S. Miller" <davem@davemloft.net>,
        LKML <linux-kernel@vger.kernel.org>
From: Aaron Lu <aaron.lu@intel.com>
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Date: Wed, 17 Aug 2016 15:42:34 +0800
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On 08/17/2016 03:35 PM, Xin Long wrote:
>>  include/net/sctp/structs.h | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
>> index d8e464aacb20..932f2780d3a4 100644
>> --- a/include/net/sctp/structs.h
>> +++ b/include/net/sctp/structs.h
>> @@ -602,6 +602,9 @@ struct sctp_chunk {
>>         /* This needs to be recoverable for SCTP_SEND_FAILED events. */
>>         struct sctp_sndrcvinfo sinfo;
>>
>> +       unsigned long prsctp_param;
>> +       int sent_count;
>> +
>>         /* Which association does this belong to?  */
>>         struct sctp_association *asoc;
>>
>> --
>> 2.5.5
>>
>> Then the performance dropped to the same as the bisected commit
>> a6c2f792873a:
>> $ cat 4.7.0-rc6-01198-g98dd2532b14e/0/netperf.json
>> {
>>   "netperf.Throughput_Mbps": [
>>    754.494375
>>   ]
>> }
>>
>> I think this agrees with the perf data in that the newly added function
>> doesn't show up in the perf-profile but still, the performance drops.
>> So the only possible reason is the newly added fields to the sctp_chunk
>> structure.
>>
>> Is this expected?
> interesting , you didn't include the modification of the functions
> parts, right ?

Yes.

> you mean only this two line:
>> +       unsigned long prsctp_param;
>> +       int sent_count;ca;
> 
> caused the performance issue ?
 
Right.