On Thursday 02 Aug 2018 at 15:04:40 (+0200), Peter Zijlstra wrote: > On Wed, Aug 01, 2018 at 10:23:27AM +0100, Quentin Perret wrote: > > 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 <[email protected]> > > > wrote: > > > > On Wednesday 01 Aug 2018 at 09:32:49 (+0200), Rafael J. Wysocki wrote: > > > >> On Tue, Jul 31, 2018 at 9:31 PM, <[email protected]> wrote: > > > >> >> On Monday 30 Jul 2018 at 12:35:27 (-0700), [email protected] > > > >> >> 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 > > Well, sugov is part of the scheduler :-) It being so allows for the > co-ordinated decision making required for EAS. > > > > 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 ? > > Right, I don't mind moving the function. What I do oppose is having two > very similar functions in different translation units -- because then > they _will_ diverge and result in 'funny' things.
Sounds good :-) Would kernel/sched/pelt.c be the right place then ? It's cross-class and kinda pelt-related I guess Thanks, Quentin
