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Message-ID: <20181120152514.GD2113@hirez.programming.kicks-ass.net>
Date: Tue, 20 Nov 2018 16:25:14 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Quentin Perret <quentin.perret@....com>, rjw@...ysocki.net,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
gregkh@...uxfoundation.org, mingo@...hat.com,
dietmar.eggemann@....com, morten.rasmussen@....com,
chris.redpath@....com, patrick.bellasi@....com,
valentin.schneider@....com, vincent.guittot@...aro.org,
thara.gopinath@...aro.org, tkjos@...gle.com,
joel@...lfernandes.org, smuckle@...gle.com,
adharmap@...eaurora.org, skannan@...eaurora.org,
pkondeti@...eaurora.org, juri.lelli@...hat.com,
edubezval@...il.com, srinivas.pandruvada@...ux.intel.com,
currojerez@...eup.net, javi.merino@...nel.org
Subject: Re: [PATCH v9 02/15] sched/cpufreq: Prepare schedutil for Energy
Aware Scheduling
On Tue, Nov 20, 2018 at 10:16:02AM +0530, Viresh Kumar wrote:
> On 19-11-18, 14:18, Quentin Perret wrote:
> > @@ -223,20 +222,33 @@ static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
>
> > - if ((util + cpu_util_dl(rq)) >= max)
> > - return max;
> > + if (type == FREQUENCY_UTIL) {
> > + /*
> > + * For frequency selection we do not make cpu_util_dl() a
> > + * permanent part of this sum because we want to use
> > + * cpu_bw_dl() later on, but we need to check if the
> > + * CFS+RT+DL sum is saturated (ie. no idle time) such
> > + * that we select f_max when there is no idle time.
> > + *
> > + * NOTE: numerical errors or stop class might cause us
> > + * to not quite hit saturation when we should --
> > + * something for later.
> > + */
> > +
> > + if ((util + cpu_util_dl(rq)) >= max)
> > + return max;
> > + } else {
> > + /*
> > + * OTOH, for energy computation we need the estimated
> > + * running time, so include util_dl and ignore dl_bw.
> > + */
> > + util += cpu_util_dl(rq);
> > + if (util >= max)
> > + return max;
> > + }
>
> Maybe write above as:
>
> dl_util = cpu_util_dl(rq);
>
> if ((util + dl_util) >= max)
> return max;
>
> if (type != FREQUENCY_UTIL)
> util += dl_util;
>
>
> as both the if/else parts were doing almost the same thing.
A little like so ?
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -201,8 +201,8 @@ static unsigned int get_next_freq(struct
unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs,
unsigned long max, enum schedutil_type type)
{
+ unsigned long dl_util, util, irq;
struct rq *rq = cpu_rq(cpu);
- unsigned long util, irq;
if (type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt))
return max;
@@ -225,30 +225,26 @@ unsigned long schedutil_freq_util(int cp
util = util_cfs;
util += cpu_util_rt(rq);
- if (type == FREQUENCY_UTIL) {
- /*
- * For frequency selection we do not make cpu_util_dl() a
- * permanent part of this sum because we want to use
- * cpu_bw_dl() later on, but we need to check if the
- * CFS+RT+DL sum is saturated (ie. no idle time) such
- * that we select f_max when there is no idle time.
- *
- * NOTE: numerical errors or stop class might cause us
- * to not quite hit saturation when we should --
- * something for later.
- */
-
- if ((util + cpu_util_dl(rq)) >= max)
- return max;
- } else {
- /*
- * OTOH, for energy computation we need the estimated
- * running time, so include util_dl and ignore dl_bw.
- */
- util += cpu_util_dl(rq);
- if (util >= max)
- return max;
- }
+ dl_util = cpu_util_dl(rq);
+
+ /*
+ * NOTE: numerical errors or stop class might cause us to not quite hit
+ * saturation when we should -- something for later.
+ */
+ if (util + dl_util > max)
+ return max;
+
+ /*
+ * For frequency selection we do not make cpu_util_dl() a permanent
+ * part of this sum because we want to use cpu_bw_dl() later on, but we
+ * need to check if the CFS+RT+DL sum is saturated (ie. no idle time)
+ * such that we select f_max when there is no idle time.
+ *
+ * OTOH, for energy computation we need the estimated running time, so
+ * do include util_dl and ignore dl_bw.
+ */
+ if (type == ENERGY_UTIL)
+ util += dl_util;
/*
* There is still idle time; further improve the number by using the
@@ -262,21 +258,18 @@ unsigned long schedutil_freq_util(int cp
util = scale_irq_capacity(util, irq, max);
util += irq;
- if (type == FREQUENCY_UTIL) {
- /*
- * Bandwidth required by DEADLINE must always be granted
- * while, for FAIR and RT, we use blocked utilization of
- * IDLE CPUs as a mechanism to gracefully reduce the
- * frequency when no tasks show up for longer periods of
- * time.
- *
- * Ideally we would like to set bw_dl as min/guaranteed
- * freq and util + bw_dl as requested freq. However,
- * cpufreq is not yet ready for such an interface. So,
- * we only do the latter for now.
- */
+ /*
+ * Bandwidth required by DEADLINE must always be granted while, for
+ * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
+ * to gracefully reduce the frequency when no tasks show up for longer
+ * periods of time.
+ *
+ * Ideally we would like to set bw_dl as min/guaranteed freq and util +
+ * bw_dl as requested freq. However, cpufreq is not yet ready for such
+ * an interface. So, we only do the latter for now.
+ */
+ if (type == FREQUENCY_UTIL)
util += cpu_bw_dl(rq);
- }
return min(max, util);
}
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