Re: [LKP] Re: [cpufreq] 909c0e9cc1: fwq.fwq.med 210.0% improvement

[Huang\, Ying]

"Rafael J. Wysocki" <rafael@xxxxxxxxxx> writes:

> On Fri, Mar 6, 2020 at 4:29 AM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>>
>> Hi, Rafael,
>>
>> "Rafael J. Wysocki" <rafael@xxxxxxxxxx> writes:
>>
>> > On Thu, Mar 5, 2020 at 9:18 AM Rong Chen <rong.a.chen@xxxxxxxxx> wrote:
>> >>
>> >>
>> >>
>> >> On 3/5/20 3:50 PM, Rafael J. Wysocki wrote:
>> >> > On 3/5/2020 2:35 AM, kernel test robot wrote:
>> >> >> Greeting,
>> >> >>
>> >> >> FYI, we noticed a 210.0% improvement of fwq.fwq.med due to commit:
>> >> >
>> >> > Well, that sounds impressive. :-)
>> >> >
>> >> >
>> >> >>
>> >> >> commit: 909c0e9cc11ba39fa5a660583b25c2431cf54deb ("cpufreq:
>> >> >> intel_pstate: Use passive mode by default without HWP")
>> >> >> https://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git
>> >> >> intel_pstate-passive
>> >> >>
>> >> >> in testcase: fwq
>> >> >> on test machine: 16 threads Intel(R) Xeon(R) CPU D-1541 @ 2.10GHz
>> >> >> with 48G memory
>> >> >> with following parameters:
>> >> >>
>> >> >>     nr_task: 100%
>> >> >>     samples: 100000ss
>> >> >>     iterations: 18x
>> >> >>     cpufreq_governor: powersave
>> >> >
>> >> > The governor should be schedutil, though, unless it is explicitly set
>> >> > to powersave in the test environment.
>> >> >
>> >> > Is that the case?
>> >> >
>> >> >
>> >>
>> >> Hi Rafael,
>> >>
>> >> Yes, we set to powersave for this test.
>> >
>> > I wonder why this is done?  Is there any particular technical reason
>> > for doing that?
>>
>> fwq is a noise benchmark to measure the hardware and software noise
>> level.  More information could be found in the following document.
>>
>> https://asc.llnl.gov/sequoia/benchmarks/FTQ_summary_v1.1.pdf
>>
>> In 0day, to measure the noise introduced by power management, we will
>> run fwq with the performance and powersave governors.  Do you think this
>> is reasonable?  Or we should use some other governors?
>
> I think that the schedutil governor should be tested too if present.
>
> Also note that for the intel_pstate driver "powersave" may mean
> different things depending on the current operation mode of the
> driver.  If scaling_driver is "intel_pstate", then "powersave" is the
> driver's built-in algorithm.  If scaling_driver is "intel_cpufreq",
> though, "powersave" means running at the minimum frequency all the
> time.

Thanks for your guidance.  We will test schedutil governor in the future
too.

As for powersave, should we stop testing it?  Or just pay attention to
the possible issue you pointed out?

Should we add ondemand governor?

Best Regards,
Huang, Ying