On 11 April 2018 at 12:15, Patrick Bellasi <patrick.bell...@arm.com> wrote: > On 11-Apr 08:57, Vincent Guittot wrote: >> On 10 April 2018 at 13:04, Patrick Bellasi <patrick.bell...@arm.com> wrote: >> > On 09-Apr 10:51, Vincent Guittot wrote: >> >> On 6 April 2018 at 19:28, Patrick Bellasi <patrick.bell...@arm.com> wrote: >> >> Peter, >> >> what was your goal with adding the condition "if >> >> (rq->cfs.h_nr_running)" for the aggragation of CFS utilization >> > >> > The original intent was to get rid of sched class flags, used to track >> > which class has tasks runnable from within schedutil. The reason was >> > to solve some misalignment between scheduler class status and >> > schedutil status. >> >> This was mainly for RT tasks but it was not the case for cfs task >> before commit 8f111bc357aa > > True, but with his solution Peter has actually come up with a unified > interface which is now (and can be IMO) based just on RUNNABLE > counters for each class.
But do we really want to only take care of runnable counter for all class ? > >> > The solution, initially suggested by Viresh, and finally proposed by >> > Peter was to exploit RQ knowledges directly from within schedutil. >> > >> > The problem is that now schedutil updated depends on two information: >> > utilization changes and number of RT and CFS runnable tasks. >> > >> > Thus, using cfs_rq::h_nr_running is not the problem... it's actually >> > part of a much more clean solution of the code we used to have. >> >> So there are 2 problems there: >> - using cfs_rq::h_nr_running when aggregating cfs utilization which >> generates a lot of frequency drop > > You mean because we now completely disregard the blocked utilization > where a CPU is idle, right? yes > > Given how PELT works and the recent support for IDLE CPUs updated, we > should probably always add contributions for the CFS class. > >> - making sure that the nr-running are up-to-date when used in sched_util > > Right... but, if we always add the cfs_rq (to always account for > blocked utilization), we don't have anymore this last dependency, > isn't it? yes > > We still have to account for the util_est dependency. > > Should I add a patch to this series to disregard cfs_rq::h_nr_running > from schedutil as you suggested? It's probably better to have a separate patch as these are 2 different topics - when updating cfs_rq::h_nr_running and when calling cpufreq_update_util - should we use runnable or running utilization for CFS Vincent, > >> > The problem, IMO is that we now depend on other information which >> > needs to be in sync before calling schedutil... and the patch I >> > proposed is meant to make it less likely that all the information >> > required are not aligned (also in the future). >> > >> > -- >> > #include <best/regards.h> >> > >> > Patrick Bellasi > > -- > #include <best/regards.h> > > Patrick Bellasi