linux-kernel - Re: [RFC PATCH v1 4/8] sched/cpufreq_schedutil: split utilization signals

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Date:   Fri, 7 Jul 2017 11:59:32 +0100
From:   Juri Lelli <juri.lelli@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     peterz@...radead.org, mingo@...hat.com, rjw@...ysocki.net,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        tglx@...utronix.de, vincent.guittot@...aro.org,
        rostedt@...dmis.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org, tkjos@...roid.com,
        joelaf@...gle.com, andresoportus@...gle.com,
        morten.rasmussen@....com, dietmar.eggemann@....com,
        patrick.bellasi@....com, Ingo Molnar <mingo@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [RFC PATCH v1 4/8] sched/cpufreq_schedutil: split utilization
 signals

Hi,

On 07/07/17 14:28, Viresh Kumar wrote:
> On 05-07-17, 09:59, Juri Lelli wrote:
> > To be able to treat utilization signals of different scheduling classes
> > in different ways (e.g., CFS signal might be stale while DEADLINE signal
> > is never stale by design) we need to split sugov_cpu::util signal in two:
> > util_cfs and util_dl.
> > 
> > This patch does that by also changing sugov_get_util() parameter list.
> > After this change, aggregation of the different signals has to be performed
> > by sugov_get_util() users (so that they can decide what to do with the
> > different signals).
> > 
> > Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Are you referring to this response here ?
> 
> https://marc.info/?l=linux-kernel&m=149095102600847&w=2
> 

Yep.

> If yes, then I don't think it was about having separate APIs, but just storing
> util_cfs/dl separately.
> 
> > -static void sugov_get_util(unsigned long *util, unsigned long *max)
> > +static void sugov_get_util(struct sugov_cpu *sg_cpu)
> >  {
> >  	struct rq *rq = this_rq();
> > -	unsigned long dl_util = (rq->dl.running_bw * SCHED_CAPACITY_SCALE)
> > -				>> BW_SHIFT;
> >  
> > -	*max = arch_scale_cpu_capacity(NULL, smp_processor_id());
> > +	sg_cpu->max = arch_scale_cpu_capacity(NULL, smp_processor_id());
> > +	sg_cpu->util_cfs = rq->cfs.avg.util_avg;
> > +	sg_cpu->util_dl = (rq->dl.running_bw * SCHED_CAPACITY_SCALE)
> > +			  >> BW_SHIFT;
> > +}
> >  
> > +static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
> 
> As Joel already mentioned, I don't think we should create two separate routines
> here.
> 

Mmm, it makes retrieving of utilization in sugov_update_shared and
aggregating values for the domain in sugov_next_freq_shared cleaner,
IMHO.

Thanks,

- Juri