Re: [PATCH 1/4] sched/fair: Be less aggressive in calling cpufreq_update_util()

[Lukasz Luba]

On 12/12/23 12:10, Qais Yousef wrote:
> On 12/11/23 07:56, Lukasz Luba wrote:
> > On 12/10/23 20:51, Qais Yousef wrote:
> > > On 12/08/23 10:05, Lukasz Luba wrote:
> > > > Hi Qais,
> > > >
> > > > On 12/8/23 01:52, Qais Yousef wrote:
> > > >
> > > > [snip]
> > > >
> > > > > @@ -6704,14 +6677,6 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
> > > > >     	 */
> > > > >     	util_est_enqueue(&rq->cfs, p);
> > > > > -	/*
> > > > > -	 * If in_iowait is set, the code below may not trigger any cpufreq
> > > > > -	 * utilization updates, so do it here explicitly with the IOWAIT flag
> > > > > -	 * passed.
> > > > > -	 */
> > > > > -	if (p->in_iowait)
> > > > > -		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
> > > > > -
> > > >
> > > > Why this io wait boost is considered as the $subject says 'aggressive'
> > > > calling?
> > >
> > > This will trigger a frequency update along with the iowait boost. Did I miss
> > > something?
> >
> > Yes, it will change CPU freq and it was the main goal for this code
> > path. We have tests which check how that works on different memory
> > types.
> >
> > Why do you want to remove it?
>
> It seems you missed this hunk? I of course didn't remove it altogether if
> that's what you mean :)
>
> 	@@ -6772,6 +6737,8 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
> 	 enqueue_throttle:
> 		assert_list_leaf_cfs_rq(rq);
>
> 	+       cpufreq_update_util(rq, p->in_iowait ? SCHED_CPUFREQ_IOWAIT : 0);
> 	+
> 		hrtick_update(rq);
> 	 }

Yes, you're right, I missed that change. I will have to spend some time
to figure out this new flow in the whole patch set.


> > Did you run some tests (e.g. fio, gallery, etc) to check if you still
> > have a decent performance out some new ufs/nvme memories?
>
> PCMark storage gives
>
> before*: 29681
> after: 30014

The result looks good.

Thanks,
Lukasz