Messages in this thread | | | Subject | Re: [PATCH 3/3] ARM: exynos_defconfig: Enable Energy Model framework | From | Lukasz Luba <> | Date | Fri, 31 Jan 2020 17:30:46 +0000 |
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Hi Krzysztof,
On 1/31/20 1:16 PM, Krzysztof Kozlowski wrote: > On Mon, 27 Jan 2020 at 22:55, <lukasz.luba@arm.com> wrote: >> >> From: Lukasz Luba <lukasz.luba@arm.com> >> >> Enable the Energy Model (EM) brings possibility to use Energy Aware >> Scheduler (EAS). This compiles the EM but does not enable to run EAS in >> default. The EAS only works with SchedUtil - a CPUFreq governor which >> handles direct requests from the scheduler for the frequency change. Thus, >> to make EAS working in default, the SchedUtil governor should be >> configured as default CPUFreq governor. > > Full stop. That's enough of needed explanation of schedutil.
OK
> >> Although, the EAS might be enabled >> in runtime, when the EM is present for CPUs, the SchedUtil is compiled and >> then set as CPUFreq governor, i.e.: >> >> echo schedutil > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor >> echo schedutil > /sys/devices/system/cpu/cpu4/cpufreq/scaling_governor >> >> To check if EAS is ready to work, the read output from the command below >> should show '1': >> cat /proc/sys/kernel/sched_energy_aware >> >> To disable EAS in runtime simply 'echo 0' to the file above. > > Not related to this commit. If you were implemeting here > schedutil/EAS, then it makes sense to post all this. However what's > the point to describe it in every defconfig change?
I will drop it.
> >> Some test results, which stress the scheduler on Odroid-XU3: >> hackbench -l 500 -s 4096 >> With mainline code and with this patch set. > > Skip the last sentence - duplicated information.
OK
> >> >> The tests have been made with and without CONFIG_PROVE_LOCKING (PL) >> (which is set to =y in default exynos_defconfig) >> >> | this patch set | mainline > > The commit will be applied on its own branch so the meaning of "this > patch set" will be lost. Maybe just "before/after"?
OK
> >> |-----------------------------------------------|--------------- >> | performance | SchedUtil | SchedUtil | performance >> | governor | governor | governor | governor >> | | w/o EAS | w/ EAS | >> ----------------|---------------|---------------|---------------|--------------- >> hackbench w/ PL | 12.7s | 11.7s | 12.0s | 13.0s - 12.2s >> hackbench w/o PL| 9.2s | 8.1s | 8.2s | 9.2s - 8.4s > > Why does the performance different before and after this patch?
Probably due to better locality and cache utilization. I can see that there is ~700k context switches vs ~450k and ~160k migrations vs ~50k. If you need to communicate two threads in different clusters, it will go through CCI.
> > Mention - lower better (?). Space between number and unit... or better > mention [s] in column title.
OK
> > And last but not least: > Why this patch is separate from 1/3? I don't get the need of splitting them.
As mentioned in response to patch 1/3. The fist patch would create MC domain, something different than Energy Model or EAS. The decisions in the scheduler would be different.
I can merge 1/3 and 3/3 if you like, though.
Regards, Lukasz
> > Best regards, > Krzysztof >
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