Re: [lkp-developer] [sched/fair] 4e5160766f: +149% ftq.noise.50% regression

[Huang, Ying <ying.huang@intel.com>]

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Hi, Vincent,

Vincent Guittot <vincent.guittot@linaro.org> writes:

> Hi Ying,
>
> On 12 December 2016 at 06:43, kernel test robot
> <ying.huang@linux.intel.com> wrote:
>> Greeting,
>>
>> FYI, we noticed a 149% regression of ftq.noise.50% due to commit:
>>
>>
>> commit: 4e5160766fcc9f41bbd38bac11f92dce993644aa ("sched/fair: Propagate asynchrous detach")
>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>>
>> in testcase: ftq
>> on test machine: 8 threads Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz with 8G memory
>> with following parameters:
>>
>>         nr_task: 100%
>>         samples: 6000ss
>>         test: cache
>>         freq: 20
>>         cpufreq_governor: powersave
>
> Why using powersave ? Are you testing  every governors ?

We will test performance and powersave governor for FTQ.

>>
>> test-description: The FTQ benchmarks measure hardware and software interference or 'noise' on a node from the applications perspective.
>> test-url: https://github.com/rminnich/ftq
>
> It's a bit difficult to understand exactly what is measured and what
> is ftq.noise.50% because this result is not part of the bench which
> seems to only record a log of data in a file and ftq.noise.50% seems
> to be lkp specific

Yes. FTQ itself has no noise statistics builtin, although it is an OS
noise benchmark.  ftq.noise.50% is calculated as below:

There is a score for every sample of ftq.  The lower the score, the
higher the noises.  ftq.noise.50% is the number (per 1000000 samples) of
samples whose score is less than 50% of the mean score.

Best Regards,
Huang, Ying

> I have tried to reproduce the lkp test on a debian jessie then a
> ubuntu server 16.10 but lkp doesn't seems to install cleanly as there
> are some errors:
>
> sudo bin/lkp run     job.yaml
> IPMI BMC is not supported on this machine, skip bmc-watchdog setup!
> 2016-12-12 13:58:39 ./ftq_cache -f 20 -n 6000 -t 8 -a 524288
> Start 5088418680237 end 5438443372098 elapsed 350024691861
> cyclestart 14236344834332 cycleend 15214154208877 elapsed 977809374545
> Avg Cycles(ticks) per ns. is 2.793544; nspercycle is 0.357968
> Pre-computed ticks per ns: 2.793541
> Sample frequency is 20.000000
> ticks per ns 2.79354
> chown: utilisateur incorrect: «lkp.lkp»
> chown: utilisateur incorrect: «lkp.lkp»
> wait for background monitors: 9405 9407 oom-killer nfs-hang
> curl: (6) Could not resolve host: ftq.time
>
>
>>
>> In addition to that, the commit also has significant impact on the following tests:
>>
>> +------------------+--------------------------------------------------------------------------------+
>> | testcase: change | unixbench: unixbench.score 2.7% improvement                                    |
>> | test machine     | 4 threads Intel(R) Core(TM) i3-3220 CPU @ 3.30GHz with 4G memory               |
>> | test parameters  | cpufreq_governor=performance                                                   |
>> |                  | nr_task=100%                                                                   |
>> |                  | runtime=300s                                                                   |
>> |                  | test=execl                                                                     |
>> +------------------+--------------------------------------------------------------------------------+
>>
>>
>> Details are as below:
>> -------------------------------------------------------------------------------------------------->
>>
>>
>> To reproduce:
>>
>>         git clone git://git.kernel.org/pub/scm/linux/kernel/git/wfg/lkp-tests.git
>>         cd lkp-tests
>>         bin/lkp install job.yaml  # job file is attached in this email
>>         bin/lkp run     job.yaml
>>
>> testcase/path_params/tbox_group/run: ftq/100%-6000ss-cache-20-powersave/lkp-hsw-d01
>>
>> 09a43ace1f986b00  4e5160766fcc9f41bbd38bac11
>> ----------------  --------------------------
>>          %stddev      change         %stddev
>>              \          |                \
>>        305 ± 30%       260%       1100 ± 14%  ftq.noise.75%
>>       1386 ± 19%       149%       3457 ±  7%  ftq.noise.50%
>>       2148 ± 11%        98%       4257 ±  4%  ftq.noise.25%
>>    3963589                     3898578        ftq.time.involuntary_context_switches
>>
>>
>>
>>                                    ftq.noise.50_
>>
>>   4000 ++------------O------------------------------------------------------+
>>        |                                                           O      O |
>>   3500 ++     O             O                        O    O O O             O
>>        | O  O      O   O      O O  O O O    O O    O   O         O          |
>>        O        O                         O                          O O    |
>>   3000 ++                                       O                           |
>>        |                 O                                                  |
>>   2500 ++                                                                   |
>>        |                                                                    |
>>   2000 ++                                                                   |
>>        |    *                  .*                                           |
>>        |   + :     *   *      *  +                                          |
>>   1500 ++ +  :    + + + +    :    + .*                                      |
>>        |.*    *. +   *   *.. :     *  +                                     |
>>   1000 *+-------*-----------*----------*------------------------------------+
>>
>>         [*] bisect-good sample
>>         [O] bisect-bad  sample
>>
>>
>> Disclaimer:
>> Results have been estimated based on internal Intel analysis and are provided
>> for informational purposes only. Any difference in system hardware or software
>> design or configuration may affect actual performance.
>>
>>
>> Thanks,
>> Ying Huang
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