Messages in this thread | | | Subject | Re: [PATCH 1/2] sched/fair: move cpufreq hook to update_cfs_rq_load_avg() | From | Steve Muckle <> | Date | Mon, 28 Mar 2016 09:34:24 -0700 |
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Hi Dietmar,
On 03/28/2016 05:02 AM, Dietmar Eggemann wrote: > Hi Steve, > > these patches fall into the bucket of 'optimization of updating the > value only if the root cfs_rq util has changed' as discussed in '[PATCH > 5/8] sched/cpufreq: pass sched class into cpufreq_update_util' of Mike > T's current series '[PATCH 0/8] schedutil enhancements', right?
I would say just the second patch is an optimization. The first and third patches cover additional paths in CFS where the hook should be called but currently is not, which I think is a correctness issue.
> I wonder if it makes sense to apply them before a proper 'capacity vote > aggregation from CFS/RT/DL' has been agreed upon?
Getting the right call sites for the hook in CFS should be orthogonal to the sched class vote aggregation IMO.
> Otherwise I agree with the changes in your 3 patches (inc. "[RFC PATCH] > sched/fair: call cpufreq hook in additional paths") to only invoke > cpufreq_update_util() if &rq->cfs.avg.util_avg has really changed. > > > On 03/22/2016 01:21 AM, Steve Muckle wrote: >> The cpufreq hook should be called whenever the root cfs_rq >> utilization changes so update_cfs_rq_load_avg() is a better >> place for it. The current location is not invoked in the >> enqueue_entity() or update_blocked_averages() paths. >> >> Suggested-by: Vincent Guittot <vincent.guittot@linaro.org> >> Signed-off-by: Steve Muckle <smuckle@linaro.org> >> --- >> kernel/sched/fair.c | 50 >> ++++++++++++++++++++++++++------------------------ >> 1 file changed, 26 insertions(+), 24 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 46d64e4ccfde..d418deb04049 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -2825,7 +2825,9 @@ static inline u64 cfs_rq_clock_task(struct >> cfs_rq *cfs_rq); >> static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq >> *cfs_rq) >> { >> struct sched_avg *sa = &cfs_rq->avg; >> + struct rq *rq = rq_of(cfs_rq); >> int decayed, removed = 0; >> + int cpu = cpu_of(rq); >> >> if (atomic_long_read(&cfs_rq->removed_load_avg)) { >> s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0); >> @@ -2840,7 +2842,7 @@ static inline int update_cfs_rq_load_avg(u64 >> now, struct cfs_rq *cfs_rq) >> sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0); >> } >> >> - decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa, >> + decayed = __update_load_avg(now, cpu, sa, >> scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, >> cfs_rq); > > Why did you change these 3 lines above? You reverted this back in "[RFC > PATCH] sched/fair: call cpufreq hook in additional paths".
If all three patches are accepted in principle I can restructure them if so desired. I did not want to introduce a dependency between them and patch 2 represents the cleanest implementation at that point.
Thanks for the review!
thanks, Steve
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