On Wednesday 01 Aug 2018 at 10:35:32 (+0200), Rafael J. Wysocki wrote: > On Wed, Aug 1, 2018 at 10:23 AM, Quentin Perret <quentin.per...@arm.com> > wrote: > > On Wednesday 01 Aug 2018 at 09:32:49 (+0200), Rafael J. Wysocki wrote: > >> On Tue, Jul 31, 2018 at 9:31 PM, <skan...@codeaurora.org> wrote: > >> >> On Monday 30 Jul 2018 at 12:35:27 (-0700), skan...@codeaurora.org wrote: > >> >>> If it's going to be a different aggregation from what's done for > >> >>> frequency > >> >>> guidance, I don't see the point of having this inside schedutil. Why > >> >>> not > >> >>> keep it inside the scheduler files? > >> >> > >> >> This code basically results from a discussion we had with Peter on v4. > >> >> Keeping everything centralized can make sense from a maintenance > >> >> perspective, I think. That makes it easy to see the impact of any change > >> >> to utilization signals for both EAS and schedutil. > >> > > >> > In that case, I'd argue it makes more sense to keep the code centralized > >> > in > >> > the scheduler. The scheduler can let schedutil know about the utilization > >> > after it aggregates them. There's no need for a cpufreq governor to know > >> > that there are scheduling classes or how many there are. And the > >> > scheduler > >> > can then choose to aggregate one way for task packing and another way for > >> > frequency guidance. > >> > >> Also the aggregate utilization may be used by cpuidle governors in > >> principle to decide how deep they can go with idle state selection. > > > > The only issue I see with this right now is that some of the things done > > in this function are policy decisions which really belong to the governor, > > I think. > > Well, the scheduler makes policy decisions too, in quite a few places. :-)
That is true ... ;-) But not so much about frequency selection yet I guess > The really important consideration here is whether or not there may be > multiple governors making different policy decisions in that respect. > If not, then where exactly the single policy decision is made doesn't > particularly matter IMO. I think some users of the aggregated utilization signal do want to make slightly different decisions (I'm thinking about the RT-go-to-max thing again which makes perfect sense in sugov, but could possibly hurt EAS). So the "hard" part of this work is to figure out what really is a governor-specific policy decision, and what is common between all users. I put "hard" between quotes because I only see the case of RT as truly sugov-specific for now. If we also want a special case for DL, Peter's enum should work OK, and enable to add more special cases for new users (cpuidle ?) if needed. But maybe that is something for later ? Thanks, Quentin
