Messages in this thread | | | Subject | Re: [PATCH 3/3] ARM: exynos_defconfig: Enable Energy Model framework | From | Lukasz Luba <> | Date | Wed, 5 Feb 2020 12:49:26 +0000 |
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Hi Krzysztof,
On 1/31/20 8:41 PM, Krzysztof Kozlowski wrote: > On Fri, Jan 31, 2020 at 05:30:46PM +0000, Lukasz Luba wrote: > >>> >>>> |-----------------------------------------------|--------------- >>>> | 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. > > Mhmm... I was not specific - I mean, "performance governor". All this > you mentioned should not differ between performance governor before and > after. However once you have 12.7, then 13.0 - 12.2. Unless multi-core > scheduler affects it... but then these numbers here are not showing > only this change, but also the SCHED_MC effect. In such case each of > commits should be coming with their own numbers.
Agree, I should have not put 'this patch set' in the commit msg. It should go into the cover letter and avoid this confusion. You are right with ' Unless multi-core scheduler affects it...', that's why when the SCHED_MC is missing, the decisions about task placing might cause this variation and delay '13.0 - 12.2' seconds.
> >> 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. > > I understand now that their independent. Still, they are part of one > goal to tune the scheduler for Exynos platform. Splitting these looks > too much, like enabling multiple drivers one after another. > > However if you provide numbers for each of cases (before patches, multi > core scheduler, energy model with DTS), then I see benefit of splitting > it. Each commit would have its own rationale. I am not sure if it is > worth such investigation - that's just defconfig... distros might ignore > it anyway.
Good point, and I agree that it would require more investigation, for which unfortunately I don't have currently spare cycles.
Should I merge patch 1/3 and 3/3 and send the v2 with a cover letter which would have the test results?
Regards, Lukasz
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