Messages in this thread Patch in this message | | | Date | Tue, 21 Dec 2021 10:09:08 +0100 | From | Vincent Donnefort <> | Subject | Re: [PATCH 1/3] sched/fair: Make cpu_overutilized() EAS dependent |
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On Mon, Dec 20, 2021 at 05:17:09PM +0000, Valentin Schneider wrote: > On 20/12/21 12:43, Vincent Donnefort wrote: > > On a system with Energy Aware Scheduling (EAS), tasks are placed according > > to their energy consumption estimation and load balancing is disabled to > > not break that energy biased placement. If the system becomes > > overutilized, i.e. one of the CPU has too much utilization, energy > > placement would then be disabled, in favor of Capacity-Aware Scheduling > > (CAS), including load balancing. This is the sole usage for > > rd->overutilized. Hence, there is no need to raise it for !EAS systems. > > > > Fixes: 2802bf3cd936 ("sched/fair: Add over-utilization/tipping point indicator") > > I'm not sure a Fixes: is warranted, this does not fix any misbehaviour or > performance regression (even if this might gain us a few extra IPS by not > writing 1's to rd->overutilized on SMP systems, note that this still gives > us writes of 0's).
I put the tag to make sure this patch would be taken for stable releases with:
[PATCH 2/3] sched/fair: Fix newidle_balance() for overutilized systems
Without the EAS requirement for cpu_overutilized() (patch 1/3), patch 2/3 could lead to useless newidle_balance() for !EAS systems.
Maybe that means in the end 2/3 and 1/3 should be squashed?
> > Regardless: > > Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> > > > Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 095b0aa378df..e2f6fa14e5e7 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -5511,7 +5511,8 @@ static inline void hrtick_update(struct rq *rq) > > #ifdef CONFIG_SMP > > static inline bool cpu_overutilized(int cpu) > > { > > - return !fits_capacity(cpu_util_cfs(cpu), capacity_of(cpu)); > > + return sched_energy_enabled() && > > + !fits_capacity(cpu_util_cfs(cpu), capacity_of(cpu)); > > } > > > > static inline void update_overutilized_status(struct rq *rq) > > -- > > 2.25.1
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