linux-kernel - Re: [LKP] Re: 2463a604a8: netperf.Throughput

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Date:   Wed, 26 May 2021 09:50:05 +0800
From:   Xing Zhengjun <zhengjun.xing@...ux.intel.com>
To:     Bart Van Assche <bvanassche@....org>,
        kernel test robot <oliver.sang@...el.com>
Cc:     0day robot <lkp@...el.com>, John Garry <john.garry@...wei.com>,
        Hannes Reinecke <hare@...e.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Christoph Hellwig <hch@....de>, linux-scsi@...r.kernel.org,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>
Subject: Re: [LKP] Re: 2463a604a8: netperf.Throughput_tps 12.8% improvement



On 5/26/2021 12:44 AM, Bart Van Assche wrote:
> On 5/24/21 11:44 PM, kernel test robot wrote:
>> FYI, we noticed a 12.8% improvement of netperf.Throughput_tps due to commit:
>>
>> commit: 2463a604a86728777ce4284214a52de46a808c9e ("[PATCH v3 2/3] Introduce enums for the SAM, message, host and driver status codes")
>> url: https://github.com/0day-ci/linux/commits/Bart-Van-Assche/Introduce-enums-for-SCSI-status-codes/20210524-105751
>> base: https://git.kernel.org/cgit/linux/kernel/git/mkp/scsi.git for-next
>>
>> in testcase: netperf
>> on test machine: 192 threads 4 sockets Intel(R) Xeon(R) Platinum 9242 CPU @ 2.30GHz with 192G memory
>> with following parameters:
>>
>> 	ip: ipv4
>> 	runtime: 300s
>> 	nr_threads: 16
>> 	cluster: cs-localhost
>> 	test: TCP_CRR
>> 	cpufreq_governor: performance
>> 	ucode: 0x5003006
>>
>> test-description: Netperf is a benchmark that can be use to measure various aspect of networking performance.
>> test-url: http://www.netperf.org/netperf/
> The above email reports a performance improvement for the networking
> subsystem while my patch only affects the SCSI subsystem and should not
> have any performance impact. I'm confused by the above feedback ...

I suspect it related with cache alignment, 2463a604a8 changes "u8" 
(size:1) to "enum xxx_status" (size: 4),  the cache alignment is better 
than before , so cause the improvement.
>
> Bart.
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> LKP mailing list -- lkp@...ts.01.org
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-- 
Zhengjun Xing