linux-kernel - Re: [ata] 0568e61225: stress-ng.copy-file.ops_per

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Date:   Fri, 12 Aug 2022 15:58:14 +0100
From:   John Garry <john.garry@...wei.com>
To:     Oliver Sang <oliver.sang@...el.com>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>
CC:     Christoph Hellwig <hch@....de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "Linux Memory Management List" <linux-mm@...ck.org>,
        <linux-ide@...r.kernel.org>, <lkp@...ts.01.org>, <lkp@...el.com>,
        <ying.huang@...el.com>, <feng.tang@...el.com>,
        <zhengjun.xing@...ux.intel.com>, <fengwei.yin@...el.com>
Subject: Re: [ata] 0568e61225: stress-ng.copy-file.ops_per_sec -15.0%
 regression

On 12/08/2022 12:13, John Garry wrote:
>> On Tue, Aug 09, 2022 at 07:55:53AM -0700, Damien Le Moal wrote:
>>> On 2022/08/09 2:58, John Garry wrote:
>>>> On 08/08/2022 15:52, Damien Le Moal wrote:
>>>>> On 2022/08/05 1:05, kernel test robot wrote:
>>>>>>
>>>>>>
>>>>>> Greeting,
>>>>>>
>>>>>> FYI, we noticed a -15.0% regression of 
>>>>>> stress-ng.copy-file.ops_per_sec due to commit:
>>>>>>
>>>>>>
>>>>>> commit: 0568e6122574dcc1aded2979cd0245038efe22b6 ("ata: 
>>>>>> libata-scsi: cap ata_device->max_sectors according to 
>>>>>> shost->max_sectors")
>>>>>> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git 
>>>>>> master
>>>>>>
>>>>>> in testcase: stress-ng
>>>>>> on test machine: 96 threads 2 sockets Ice Lake with 256G memory
>>>>>> with following parameters:
>>>>>>
>>>>>>     nr_threads: 10%
>>>>>>     disk: 1HDD
>>>>>>     testtime: 60s
>>>>>>     fs: f2fs
>>>>>>     class: filesystem
>>>>>>     test: copy-file
>>>>>>     cpufreq_governor: performance
>>>>>>     ucode: 0xb000280
>>>>>
>>>>> Without knowing what the device adapter is, hard to say where the 
>>>>> problem is. I
>>>>> suspect that with the patch applied, we may be ending up with a 
>>>>> small default
>>>>> max_sectors value, causing overhead due to more commands than 
>>>>> necessary.
>>>>>
>>>>> Will check what I see with my test rig.
>>>>
>>>> As far as I can see, this patch should not make a difference unless the
>>>> ATA shost driver is setting the max_sectors value unnecessarily low.
>>>
>>> That is my hunch too, hence my question about which host driver is 
>>> being used
>>> for this test... That is not apparent from the problem report.
>>
>> we noticed the commit is already in mainline now, and in our tests, 
>> there is
>> still similar regression and also on other platforms.
>> could you guide us how to check "which host driver is being used for this
>> test"? hope to supply some useful information.
>>
> 
> For me, a complete kernel log may help.

and since only 1HDD, the output of the following would be helpful:

/sys/block/sda/queue/max_sectors_kb
/sys/block/sda/queue/max_hw_sectors_kb

And for 5.19, if possible.

Thanks!

> 
>>>
>>>>