Messages in this thread | | | Date | Wed, 30 Jun 2021 15:11:22 +0100 | From | Qais Yousef <> | Subject | Re: [PATCH] sched/uclamp: Fix getting unreasonable ucalmp_max when rq is idle |
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Thanks for the CC.
On 06/30/21 09:24, Xuewen Yan wrote: > On Tue, Jun 29, 2021 at 9:50 PM Valentin Schneider > <valentin.schneider@arm.com> wrote: > > > > > > +Cc Patrick's current address > > > > On 18/06/21 15:23, Xuewen Yan wrote: > > > From: Xuewen Yan <xuewen.yan@unisoc.com> > > > > > > Now in uclamp_rq_util_with(), when the task != NULL, the uclamp_max as following: > > > uc_rq_max = rq->uclamp[UCLAMP_MAX].value; > > > uc_eff_max = uclamp_eff_value(p, UCLAMP_MAX); > > > uclamp_max = max{uc_rq_max, uc_eff_max}; > > > > > > Consider the following scenario: > > > (1)the rq is idle, the uc_rq_max is last task's UCLAMP_MAX; > > > (2)the p's uc_eff_max < uc_rq_max. > > > > > > The result is the uclamp_max = uc_rq_max instead of uc_eff_max, it is unreasonable. > > > > > > The scenario often happens in find_energy_efficient_cpu(), when the task has smaller UCLAMP_MAX. > > > > > > Inserts whether the rq is idle in the uclamp_rq_util_with(). > > > > > > Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com> > > > --- > > > kernel/sched/sched.h | 5 ++++- > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > > > index a189bec13729..0feef6af89f2 100644 > > > --- a/kernel/sched/sched.h > > > +++ b/kernel/sched/sched.h > > > @@ -2550,7 +2550,10 @@ unsigned long uclamp_rq_util_with(struct rq *rq, unsigned long util, > > > > > > if (p) { > > > min_util = max(min_util, uclamp_eff_value(p, UCLAMP_MIN)); > > > - max_util = max(max_util, uclamp_eff_value(p, UCLAMP_MAX)); > > > + if (rq->uclamp_flags & UCLAMP_FLAG_IDLE) > > > + max_util = uclamp_eff_value(p, UCLAMP_MAX); > > > + else > > > + max_util = max(max_util, uclamp_eff_value(p, UCLAMP_MAX)); > > > > That makes sense to me - enqueuing the task will lift UCLAMP_FLAG_IDLE and > > set the rq clamp as the task's via uclamp_idle_reset(). > > > > Does this want a > > > > Fixes: 9d20ad7dfc9a ("sched/uclamp: Add uclamp_util_with()") > > > > ? > > Yes,add it.
+1
> > > > > Also, when we have UCLAMP_FLAG_IDLE, we don't even need to read the rq max > > - and I'm pretty sure the same applies to the rq min. What about something like:
uclamp_min is fine since it defaults to 0. But the suggested improvement looks good to me.
Thanks
-- Qais Yousef
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