Re: [ata] 0568e61225: stress-ng.copy-file.ops_per_sec -15.0% regression

John Garry
2022-08-12T14:58:22Z

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!

>
>>>
>>>>