Messages in this thread | | | Date | Thu, 26 Apr 2018 12:15:33 +0100 | From | Patrick Bellasi <> | Subject | Re: [PATCH] sched/fair: schedutil: update only with all info available |
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On 11-Apr 17:37, Peter Zijlstra wrote: > On Wed, Apr 11, 2018 at 05:29:01PM +0200, Vincent Guittot wrote: > > On 11 April 2018 at 17:14, Peter Zijlstra <peterz@infradead.org> wrote: > > > On Tue, Apr 10, 2018 at 12:04:12PM +0100, Patrick Bellasi wrote: > > >> On 09-Apr 10:51, Vincent Guittot 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. > > >> > > >> 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. > > >> > > >> 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). > > > > > > Specifically, the h_nr_running test was get rid of > > > > > > if (delta_ns > TICK_NSEC) { > > > j_sg_cpu->iowait_boost = 0; > > > j_sg_cpu->iowait_boost_pending = false; > > > - j_sg_cpu->util_cfs = 0; > > > > > > ^^^^^^^^^^^^^^^^^^^^^^^ that.. > > > > > > - if (j_sg_cpu->util_dl == 0) > > > - continue; > > > } > > > > > > > > > because that felt rather arbitrary. > > > > yes I agree. > > > > With the patch that updates blocked idle load, we should not have the > > problem of blocked utilization anymore and get rid of the code above > > and h_nr_running test > > Yes, these patches predate those, but indeed, now that we age the > blocked load consistently it should no longer be required.
After this discussion, I think there is a general consensus about always add sg_cpu->util_cfs in cpufreq_schedutil.c::sugov_aggregate_util.
Is that right?
For the rest, what this patch proposes is a code reorganization which is not required anymore to fix this specific issue but, it's still required to fix the other issue reported by Vincent: i.e. util_est is not updated before schedutil.
Thus, I would propose to still keep this refactoring but in the context of a different patch to specifically fixes the util_est case.
If there are not major complains, I'll post a new series in the next few days.
-- #include <best/regards.h>
Patrick Bellasi
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