* [PATCH v9 01/15] sched: Relocate arch_scale_cpu_capacity
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 02/15] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling Quentin Perret
` (13 subsequent siblings)
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
By default, arch_scale_cpu_capacity() is only visible from within the
kernel/sched folder. Relocate it to include/linux/sched/topology.h to
make it visible to other clients needing to know about the capacity of
CPUs, such as the Energy Model framework.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
include/linux/sched/topology.h | 19 +++++++++++++++++++
kernel/sched/sched.h | 21 ---------------------
2 files changed, 19 insertions(+), 21 deletions(-)
diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index 6b9976180c1e..5e56d6b1e217 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -202,6 +202,17 @@ extern void set_sched_topology(struct sched_domain_topology_level *tl);
# define SD_INIT_NAME(type)
#endif
+#ifndef arch_scale_cpu_capacity
+static __always_inline
+unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
+{
+ if (sd && (sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
+ return sd->smt_gain / sd->span_weight;
+
+ return SCHED_CAPACITY_SCALE;
+}
+#endif
+
#else /* CONFIG_SMP */
struct sched_domain_attr;
@@ -217,6 +228,14 @@ static inline bool cpus_share_cache(int this_cpu, int that_cpu)
return true;
}
+#ifndef arch_scale_cpu_capacity
+static __always_inline
+unsigned long arch_scale_cpu_capacity(void __always_unused *sd, int cpu)
+{
+ return SCHED_CAPACITY_SCALE;
+}
+#endif
+
#endif /* !CONFIG_SMP */
static inline int task_node(const struct task_struct *p)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e0e052a50fcd..7adee78dc29d 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1861,27 +1861,6 @@ unsigned long arch_scale_freq_capacity(int cpu)
}
#endif
-#ifdef CONFIG_SMP
-#ifndef arch_scale_cpu_capacity
-static __always_inline
-unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
-{
- if (sd && (sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
- return sd->smt_gain / sd->span_weight;
-
- return SCHED_CAPACITY_SCALE;
-}
-#endif
-#else
-#ifndef arch_scale_cpu_capacity
-static __always_inline
-unsigned long arch_scale_cpu_capacity(void __always_unused *sd, int cpu)
-{
- return SCHED_CAPACITY_SCALE;
-}
-#endif
-#endif
-
#ifdef CONFIG_SMP
#ifdef CONFIG_PREEMPT
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 02/15] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
2018-11-19 14:18 ` [PATCH v9 01/15] sched: Relocate arch_scale_cpu_capacity Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-20 4:46 ` Viresh Kumar
2018-11-19 14:18 ` [PATCH v9 03/15] PM: Introduce an Energy Model management framework Quentin Perret
` (12 subsequent siblings)
14 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
Schedutil requests frequency by aggregating utilization signals from
the scheduler (CFS, RT, DL, IRQ) and applying a 25% margin on top of
them. Since Energy Aware Scheduling (EAS) needs to be able to predict
the frequency requests, it needs to forecast the decisions made by the
governor.
In order to prepare the introduction of EAS, introduce
schedutil_freq_util() to centralize the aforementioned signal
aggregation and make it available to both schedutil and EAS. Since
frequency selection and energy estimation still need to deal with RT and
DL signals slightly differently, schedutil_freq_util() is called with a
different 'type' parameter in those two contexts, and returns an
aggregated utilization signal accordingly. While at it, introduce the
map_util_freq() function which is designed to make schedutil's 25%
margin usable easily for both sugov and EAS.
As EAS will be able to predict schedutil's frequency requests more
accurately than any other governor by design, it'd be sensible to make
sure EAS cannot be used without schedutil. This will be done later, once
EAS has actually been introduced.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
include/linux/sched/cpufreq.h | 6 +++
kernel/sched/cpufreq_schedutil.c | 92 +++++++++++++++++++++-----------
kernel/sched/sched.h | 30 +++++++++++
3 files changed, 97 insertions(+), 31 deletions(-)
diff --git a/include/linux/sched/cpufreq.h b/include/linux/sched/cpufreq.h
index 59667444669f..afa940cd50dc 100644
--- a/include/linux/sched/cpufreq.h
+++ b/include/linux/sched/cpufreq.h
@@ -20,6 +20,12 @@ void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
void (*func)(struct update_util_data *data, u64 time,
unsigned int flags));
void cpufreq_remove_update_util_hook(int cpu);
+
+static inline unsigned long map_util_freq(unsigned long util,
+ unsigned long freq, unsigned long cap)
+{
+ return (freq + (freq >> 2)) * util / cap;
+}
#endif /* CONFIG_CPU_FREQ */
#endif /* _LINUX_SCHED_CPUFREQ_H */
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 3fffad3bc8a8..105cf70fcb69 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -13,6 +13,7 @@
#include "sched.h"
+#include <linux/sched/cpufreq.h>
#include <trace/events/power.h>
struct sugov_tunables {
@@ -167,7 +168,7 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
unsigned int freq = arch_scale_freq_invariant() ?
policy->cpuinfo.max_freq : policy->cur;
- freq = (freq + (freq >> 2)) * util / max;
+ freq = map_util_freq(util, freq, max);
if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update)
return sg_policy->next_freq;
@@ -197,15 +198,13 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
* based on the task model parameters and gives the minimal utilization
* required to meet deadlines.
*/
-static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
+unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs,
+ unsigned long max, enum schedutil_type type)
{
- struct rq *rq = cpu_rq(sg_cpu->cpu);
- unsigned long util, irq, max;
-
- sg_cpu->max = max = arch_scale_cpu_capacity(NULL, sg_cpu->cpu);
- sg_cpu->bw_dl = cpu_bw_dl(rq);
+ struct rq *rq = cpu_rq(cpu);
+ unsigned long util, irq;
- if (rt_rq_is_runnable(&rq->rt))
+ if (type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt))
return max;
/*
@@ -223,20 +222,33 @@ static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
* utilization (PELT windows are synchronized) we can directly add them
* to obtain the CPU's actual utilization.
*/
- util = cpu_util_cfs(rq);
+ util = util_cfs;
util += cpu_util_rt(rq);
- /*
- * 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;
+ 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;
+ }
/*
* There is still idle time; further improve the number by using the
@@ -250,17 +262,35 @@ static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
util = scale_irq_capacity(util, irq, max);
util += irq;
- /*
- * 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.
- */
- return min(max, util + sg_cpu->bw_dl);
+ 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.
+ */
+ util += cpu_bw_dl(rq);
+ }
+
+ return min(max, util);
+}
+
+static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
+{
+ struct rq *rq = cpu_rq(sg_cpu->cpu);
+ unsigned long util = cpu_util_cfs(rq);
+ unsigned long max = arch_scale_cpu_capacity(NULL, sg_cpu->cpu);
+
+ sg_cpu->max = max;
+ sg_cpu->bw_dl = cpu_bw_dl(rq);
+
+ return schedutil_freq_util(sg_cpu->cpu, util, max, FREQUENCY_UTIL);
}
/**
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 7adee78dc29d..9d28d66dd707 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2193,6 +2193,31 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
#endif
#ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL
+/**
+ * enum schedutil_type - CPU utilization type
+ * @FREQUENCY_UTIL: Utilization used to select frequency
+ * @ENERGY_UTIL: Utilization used during energy calculation
+ *
+ * The utilization signals of all scheduling classes (CFS/RT/DL) and IRQ time
+ * need to be aggregated differently depending on the usage made of them. This
+ * enum is used within schedutil_freq_util() to differentiate the types of
+ * utilization expected by the callers, and adjust the aggregation accordingly.
+ */
+enum schedutil_type {
+ FREQUENCY_UTIL,
+ ENERGY_UTIL,
+};
+
+unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs,
+ unsigned long max, enum schedutil_type type);
+
+static inline unsigned long schedutil_energy_util(int cpu, unsigned long cfs)
+{
+ unsigned long max = arch_scale_cpu_capacity(NULL, cpu);
+
+ return schedutil_freq_util(cpu, cfs, max, ENERGY_UTIL);
+}
+
static inline unsigned long cpu_bw_dl(struct rq *rq)
{
return (rq->dl.running_bw * SCHED_CAPACITY_SCALE) >> BW_SHIFT;
@@ -2219,6 +2244,11 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
{
return READ_ONCE(rq->avg_rt.util_avg);
}
+#else /* CONFIG_CPU_FREQ_GOV_SCHEDUTIL */
+static inline unsigned long schedutil_energy_util(int cpu, unsigned long cfs)
+{
+ return cfs;
+}
#endif
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* Re: [PATCH v9 02/15] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling
2018-11-19 14:18 ` [PATCH v9 02/15] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling Quentin Perret
@ 2018-11-20 4:46 ` Viresh Kumar
2018-11-20 15:25 ` Peter Zijlstra
0 siblings, 1 reply; 35+ messages in thread
From: Viresh Kumar @ 2018-11-20 4:46 UTC (permalink / raw)
To: Quentin Perret
Cc: peterz, rjw, linux-kernel, linux-pm, gregkh, mingo,
dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, tkjos, joel, smuckle, adharmap, skannan,
pkondeti, juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
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.
--
viresh
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 02/15] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling
2018-11-20 4:46 ` Viresh Kumar
@ 2018-11-20 15:25 ` Peter Zijlstra
2018-11-20 15:53 ` Quentin Perret
0 siblings, 1 reply; 35+ messages in thread
From: Peter Zijlstra @ 2018-11-20 15:25 UTC (permalink / raw)
To: Viresh Kumar
Cc: Quentin Perret, rjw, linux-kernel, linux-pm, gregkh, mingo,
dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, tkjos, joel, smuckle, adharmap, skannan,
pkondeti, juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
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);
}
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 02/15] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling
2018-11-20 15:25 ` Peter Zijlstra
@ 2018-11-20 15:53 ` Quentin Perret
0 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-20 15:53 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Viresh Kumar, rjw, linux-kernel, linux-pm, gregkh, mingo,
dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, tkjos, joel, smuckle, adharmap, skannan,
pkondeti, juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Tuesday 20 Nov 2018 at 16:25:14 (+0100), Peter Zijlstra wrote:
> 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.
We probably want move that paragraph to the comment above no ? Other
than that, the change LGTM.
> + *
> + * 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);
> }
Thanks,
Quentin
^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH v9 03/15] PM: Introduce an Energy Model management framework
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
2018-11-19 14:18 ` [PATCH v9 01/15] sched: Relocate arch_scale_cpu_capacity Quentin Perret
2018-11-19 14:18 ` [PATCH v9 02/15] sched/cpufreq: Prepare schedutil for Energy Aware Scheduling Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 04/15] PM / EM: Expose the Energy Model in sysfs Quentin Perret
` (11 subsequent siblings)
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
Several subsystems in the kernel (task scheduler and/or thermal at the
time of writing) can benefit from knowing about the energy consumed by
CPUs. Yet, this information can come from different sources (DT or
firmware for example), in different formats, hence making it hard to
exploit without a standard API.
As an attempt to address this, introduce a centralized Energy Model
(EM) management framework which aggregates the power values provided
by drivers into a table for each performance domain in the system. The
power cost tables are made available to interested clients (e.g. task
scheduler or thermal) via platform-agnostic APIs. The overall design
is represented by the diagram below (focused on Arm-related drivers as
an example, but applicable to any architecture):
+---------------+ +-----------------+ +-------------+
| Thermal (IPA) | | Scheduler (EAS) | | Other |
+---------------+ +-----------------+ +-------------+
| | em_pd_energy() |
| | em_cpu_get() |
+-----------+ | +--------+
| | |
v v v
+---------------------+
| |
| Energy Model |
| |
| Framework |
| |
+---------------------+
^ ^ ^
| | | em_register_perf_domain()
+----------+ | +---------+
| | |
+---------------+ +---------------+ +--------------+
| cpufreq-dt | | arm_scmi | | Other |
+---------------+ +---------------+ +--------------+
^ ^ ^
| | |
+--------------+ +---------------+ +--------------+
| Device Tree | | Firmware | | ? |
+--------------+ +---------------+ +--------------+
Drivers (typically, but not limited to, CPUFreq drivers) can register
data in the EM framework using the em_register_perf_domain() API. The
calling driver must provide a callback function with a standardized
signature that will be used by the EM framework to build the power
cost tables of the performance domain. This design should offer a lot of
flexibility to calling drivers which are free of reading information
from any location and to use any technique to compute power costs.
Moreover, the capacity states registered by drivers in the EM framework
are not required to match real performance states of the target. This
is particularly important on targets where the performance states are
not known by the OS.
The power cost coefficients managed by the EM framework are specified in
milli-watts. Although the two potential users of those coefficients (IPA
and EAS) only need relative correctness, IPA specifically needs to
compare the power of CPUs with the power of other components (GPUs, for
example), which are still expressed in absolute terms in their
respective subsystems. Hence, specifying the power of CPUs in
milli-watts should help transitioning IPA to using the EM framework
without introducing new problems by keeping units comparable across
sub-systems.
On the longer term, the EM of other devices than CPUs could also be
managed by the EM framework, which would enable to remove the absolute
unit. However, this is not absolutely required as a first step, so this
extension of the EM framework is left for later.
On the client side, the EM framework offers APIs to access the power
cost tables of a CPU (em_cpu_get()), and to estimate the energy
consumed by the CPUs of a performance domain (em_pd_energy()). Clients
such as the task scheduler can then use these APIs to access the shared
data structures holding the Energy Model of CPUs.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
include/linux/energy_model.h | 187 ++++++++++++++++++++++++++++++++
kernel/power/Kconfig | 15 +++
kernel/power/Makefile | 2 +
kernel/power/energy_model.c | 201 +++++++++++++++++++++++++++++++++++
4 files changed, 405 insertions(+)
create mode 100644 include/linux/energy_model.h
create mode 100644 kernel/power/energy_model.c
diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
new file mode 100644
index 000000000000..aa027f7bcb3e
--- /dev/null
+++ b/include/linux/energy_model.h
@@ -0,0 +1,187 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_ENERGY_MODEL_H
+#define _LINUX_ENERGY_MODEL_H
+#include <linux/cpumask.h>
+#include <linux/jump_label.h>
+#include <linux/kobject.h>
+#include <linux/rcupdate.h>
+#include <linux/sched/cpufreq.h>
+#include <linux/sched/topology.h>
+#include <linux/types.h>
+
+#ifdef CONFIG_ENERGY_MODEL
+/**
+ * em_cap_state - Capacity state of a performance domain
+ * @frequency: The CPU frequency in KHz, for consistency with CPUFreq
+ * @power: The power consumed by 1 CPU at this level, in milli-watts
+ * @cost: The cost coefficient associated with this level, used during
+ * energy calculation. Equal to: power * max_frequency / frequency
+ */
+struct em_cap_state {
+ unsigned long frequency;
+ unsigned long power;
+ unsigned long cost;
+};
+
+/**
+ * em_perf_domain - Performance domain
+ * @table: List of capacity states, in ascending order
+ * @nr_cap_states: Number of capacity states
+ * @cpus: Cpumask covering the CPUs of the domain
+ *
+ * A "performance domain" represents a group of CPUs whose performance is
+ * scaled together. All CPUs of a performance domain must have the same
+ * micro-architecture. Performance domains often have a 1-to-1 mapping with
+ * CPUFreq policies.
+ */
+struct em_perf_domain {
+ struct em_cap_state *table;
+ int nr_cap_states;
+ unsigned long cpus[0];
+};
+
+#define EM_CPU_MAX_POWER 0xFFFF
+
+struct em_data_callback {
+ /**
+ * active_power() - Provide power at the next capacity state of a CPU
+ * @power : Active power at the capacity state in mW (modified)
+ * @freq : Frequency at the capacity state in kHz (modified)
+ * @cpu : CPU for which we do this operation
+ *
+ * active_power() must find the lowest capacity state of 'cpu' above
+ * 'freq' and update 'power' and 'freq' to the matching active power
+ * and frequency.
+ *
+ * The power is the one of a single CPU in the domain, expressed in
+ * milli-watts. It is expected to fit in the [0, EM_CPU_MAX_POWER]
+ * range.
+ *
+ * Return 0 on success.
+ */
+ int (*active_power)(unsigned long *power, unsigned long *freq, int cpu);
+};
+#define EM_DATA_CB(_active_power_cb) { .active_power = &_active_power_cb }
+
+struct em_perf_domain *em_cpu_get(int cpu);
+int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
+ struct em_data_callback *cb);
+
+/**
+ * em_pd_energy() - Estimates the energy consumed by the CPUs of a perf. domain
+ * @pd : performance domain for which energy has to be estimated
+ * @max_util : highest utilization among CPUs of the domain
+ * @sum_util : sum of the utilization of all CPUs in the domain
+ *
+ * Return: the sum of the energy consumed by the CPUs of the domain assuming
+ * a capacity state satisfying the max utilization of the domain.
+ */
+static inline unsigned long em_pd_energy(struct em_perf_domain *pd,
+ unsigned long max_util, unsigned long sum_util)
+{
+ unsigned long freq, scale_cpu;
+ struct em_cap_state *cs;
+ int i, cpu;
+
+ /*
+ * In order to predict the capacity state, map the utilization of the
+ * most utilized CPU of the performance domain to a requested frequency,
+ * like schedutil.
+ */
+ cpu = cpumask_first(to_cpumask(pd->cpus));
+ scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
+ cs = &pd->table[pd->nr_cap_states - 1];
+ freq = map_util_freq(max_util, cs->frequency, scale_cpu);
+
+ /*
+ * Find the lowest capacity state of the Energy Model above the
+ * requested frequency.
+ */
+ for (i = 0; i < pd->nr_cap_states; i++) {
+ cs = &pd->table[i];
+ if (cs->frequency >= freq)
+ break;
+ }
+
+ /*
+ * The capacity of a CPU in the domain at that capacity state (cs)
+ * can be computed as:
+ *
+ * cs->freq * scale_cpu
+ * cs->cap = -------------------- (1)
+ * cpu_max_freq
+ *
+ * So, ignoring the costs of idle states (which are not available in
+ * the EM), the energy consumed by this CPU at that capacity state is
+ * estimated as:
+ *
+ * cs->power * cpu_util
+ * cpu_nrg = -------------------- (2)
+ * cs->cap
+ *
+ * since 'cpu_util / cs->cap' represents its percentage of busy time.
+ *
+ * NOTE: Although the result of this computation actually is in
+ * units of power, it can be manipulated as an energy value
+ * over a scheduling period, since it is assumed to be
+ * constant during that interval.
+ *
+ * By injecting (1) in (2), 'cpu_nrg' can be re-expressed as a product
+ * of two terms:
+ *
+ * cs->power * cpu_max_freq cpu_util
+ * cpu_nrg = ------------------------ * --------- (3)
+ * cs->freq scale_cpu
+ *
+ * The first term is static, and is stored in the em_cap_state struct
+ * as 'cs->cost'.
+ *
+ * Since all CPUs of the domain have the same micro-architecture, they
+ * share the same 'cs->cost', and the same CPU capacity. Hence, the
+ * total energy of the domain (which is the simple sum of the energy of
+ * all of its CPUs) can be factorized as:
+ *
+ * cs->cost * \Sum cpu_util
+ * pd_nrg = ------------------------ (4)
+ * scale_cpu
+ */
+ return cs->cost * sum_util / scale_cpu;
+}
+
+/**
+ * em_pd_nr_cap_states() - Get the number of capacity states of a perf. domain
+ * @pd : performance domain for which this must be done
+ *
+ * Return: the number of capacity states in the performance domain table
+ */
+static inline int em_pd_nr_cap_states(struct em_perf_domain *pd)
+{
+ return pd->nr_cap_states;
+}
+
+#else
+struct em_perf_domain {};
+struct em_data_callback {};
+#define EM_DATA_CB(_active_power_cb) { }
+
+static inline int em_register_perf_domain(cpumask_t *span,
+ unsigned int nr_states, struct em_data_callback *cb)
+{
+ return -EINVAL;
+}
+static inline struct em_perf_domain *em_cpu_get(int cpu)
+{
+ return NULL;
+}
+static inline unsigned long em_pd_energy(struct em_perf_domain *pd,
+ unsigned long max_util, unsigned long sum_util)
+{
+ return 0;
+}
+static inline int em_pd_nr_cap_states(struct em_perf_domain *pd)
+{
+ return 0;
+}
+#endif
+
+#endif
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 3a6c2f87699e..f8fe57d1022e 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -298,3 +298,18 @@ config PM_GENERIC_DOMAINS_OF
config CPU_PM
bool
+
+config ENERGY_MODEL
+ bool "Energy Model for CPUs"
+ depends on SMP
+ depends on CPU_FREQ
+ default n
+ help
+ Several subsystems (thermal and/or the task scheduler for example)
+ can leverage information about the energy consumed by CPUs to make
+ smarter decisions. This config option enables the framework from
+ which subsystems can access the energy models.
+
+ The exact usage of the energy model is subsystem-dependent.
+
+ If in doubt, say N.
diff --git a/kernel/power/Makefile b/kernel/power/Makefile
index a3f79f0eef36..e7e47d9be1e5 100644
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -15,3 +15,5 @@ obj-$(CONFIG_PM_AUTOSLEEP) += autosleep.o
obj-$(CONFIG_PM_WAKELOCKS) += wakelock.o
obj-$(CONFIG_MAGIC_SYSRQ) += poweroff.o
+
+obj-$(CONFIG_ENERGY_MODEL) += energy_model.o
diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
new file mode 100644
index 000000000000..d9dc2c38764a
--- /dev/null
+++ b/kernel/power/energy_model.c
@@ -0,0 +1,201 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Energy Model of CPUs
+ *
+ * Copyright (c) 2018, Arm ltd.
+ * Written by: Quentin Perret, Arm ltd.
+ */
+
+#define pr_fmt(fmt) "energy_model: " fmt
+
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/energy_model.h>
+#include <linux/sched/topology.h>
+#include <linux/slab.h>
+
+/* Mapping of each CPU to the performance domain to which it belongs. */
+static DEFINE_PER_CPU(struct em_perf_domain *, em_data);
+
+/*
+ * Mutex serializing the registrations of performance domains and letting
+ * callbacks defined by drivers sleep.
+ */
+static DEFINE_MUTEX(em_pd_mutex);
+
+static struct em_perf_domain *em_create_pd(cpumask_t *span, int nr_states,
+ struct em_data_callback *cb)
+{
+ unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
+ unsigned long power, freq, prev_freq = 0;
+ int i, ret, cpu = cpumask_first(span);
+ struct em_cap_state *table;
+ struct em_perf_domain *pd;
+ u64 fmax;
+
+ if (!cb->active_power)
+ return NULL;
+
+ pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
+ if (!pd)
+ return NULL;
+
+ table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
+ if (!table)
+ goto free_pd;
+
+ /* Build the list of capacity states for this performance domain */
+ for (i = 0, freq = 0; i < nr_states; i++, freq++) {
+ /*
+ * active_power() is a driver callback which ceils 'freq' to
+ * lowest capacity state of 'cpu' above 'freq' and updates
+ * 'power' and 'freq' accordingly.
+ */
+ ret = cb->active_power(&power, &freq, cpu);
+ if (ret) {
+ pr_err("pd%d: invalid cap. state: %d\n", cpu, ret);
+ goto free_cs_table;
+ }
+
+ /*
+ * We expect the driver callback to increase the frequency for
+ * higher capacity states.
+ */
+ if (freq <= prev_freq) {
+ pr_err("pd%d: non-increasing freq: %lu\n", cpu, freq);
+ goto free_cs_table;
+ }
+
+ /*
+ * The power returned by active_state() is expected to be
+ * positive, in milli-watts and to fit into 16 bits.
+ */
+ if (!power || power > EM_CPU_MAX_POWER) {
+ pr_err("pd%d: invalid power: %lu\n", cpu, power);
+ goto free_cs_table;
+ }
+
+ table[i].power = power;
+ table[i].frequency = prev_freq = freq;
+
+ /*
+ * The hertz/watts efficiency ratio should decrease as the
+ * frequency grows on sane platforms. But this isn't always
+ * true in practice so warn the user if a higher OPP is more
+ * power efficient than a lower one.
+ */
+ opp_eff = freq / power;
+ if (opp_eff >= prev_opp_eff)
+ pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_cap_state %d >= em_cap_state%d\n",
+ cpu, i, i - 1);
+ prev_opp_eff = opp_eff;
+ }
+
+ /* Compute the cost of each capacity_state. */
+ fmax = (u64) table[nr_states - 1].frequency;
+ for (i = 0; i < nr_states; i++) {
+ table[i].cost = div64_u64(fmax * table[i].power,
+ table[i].frequency);
+ }
+
+ pd->table = table;
+ pd->nr_cap_states = nr_states;
+ cpumask_copy(to_cpumask(pd->cpus), span);
+
+ return pd;
+
+free_cs_table:
+ kfree(table);
+free_pd:
+ kfree(pd);
+
+ return NULL;
+}
+
+/**
+ * em_cpu_get() - Return the performance domain for a CPU
+ * @cpu : CPU to find the performance domain for
+ *
+ * Return: the performance domain to which 'cpu' belongs, or NULL if it doesn't
+ * exist.
+ */
+struct em_perf_domain *em_cpu_get(int cpu)
+{
+ return READ_ONCE(per_cpu(em_data, cpu));
+}
+EXPORT_SYMBOL_GPL(em_cpu_get);
+
+/**
+ * em_register_perf_domain() - Register the Energy Model of a performance domain
+ * @span : Mask of CPUs in the performance domain
+ * @nr_states : Number of capacity states to register
+ * @cb : Callback functions providing the data of the Energy Model
+ *
+ * Create Energy Model tables for a performance domain using the callbacks
+ * defined in cb.
+ *
+ * If multiple clients register the same performance domain, all but the first
+ * registration will be ignored.
+ *
+ * Return 0 on success
+ */
+int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
+ struct em_data_callback *cb)
+{
+ unsigned long cap, prev_cap = 0;
+ struct em_perf_domain *pd;
+ int cpu, ret = 0;
+
+ if (!span || !nr_states || !cb)
+ return -EINVAL;
+
+ /*
+ * Use a mutex to serialize the registration of performance domains and
+ * let the driver-defined callback functions sleep.
+ */
+ mutex_lock(&em_pd_mutex);
+
+ for_each_cpu(cpu, span) {
+ /* Make sure we don't register again an existing domain. */
+ if (READ_ONCE(per_cpu(em_data, cpu))) {
+ ret = -EEXIST;
+ goto unlock;
+ }
+
+ /*
+ * All CPUs of a domain must have the same micro-architecture
+ * since they all share the same table.
+ */
+ cap = arch_scale_cpu_capacity(NULL, cpu);
+ if (prev_cap && prev_cap != cap) {
+ pr_err("CPUs of %*pbl must have the same capacity\n",
+ cpumask_pr_args(span));
+ ret = -EINVAL;
+ goto unlock;
+ }
+ prev_cap = cap;
+ }
+
+ /* Create the performance domain and add it to the Energy Model. */
+ pd = em_create_pd(span, nr_states, cb);
+ if (!pd) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ for_each_cpu(cpu, span) {
+ /*
+ * The per-cpu array can be read concurrently from em_cpu_get().
+ * The barrier enforces the ordering needed to make sure readers
+ * can only access well formed em_perf_domain structs.
+ */
+ smp_store_release(per_cpu_ptr(&em_data, cpu), pd);
+ }
+
+ pr_debug("Created perf domain %*pbl\n", cpumask_pr_args(span));
+unlock:
+ mutex_unlock(&em_pd_mutex);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(em_register_perf_domain);
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 04/15] PM / EM: Expose the Energy Model in sysfs
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (2 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 03/15] PM: Introduce an Energy Model management framework Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 05/15] sched/topology: Reference the Energy Model of CPUs when available Quentin Perret
` (10 subsequent siblings)
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
Expose the Energy Model (read-only) of all performance domains in sysfs
for convenience. To do so, add a kobject to the CPU subsystem under the
umbrella of which a kobject for each performance domain is attached.
The resulting hierarchy is as follows for a platform with two
performance domains for example:
/sys/devices/system/cpu/energy_model
├── pd0
│ ├── cost
│ ├── cpus
│ ├── frequency
│ └── power
└── pd4
├── cost
├── cpus
├── frequency
└── power
In this implementation, the kobject abstraction is only used as a
convenient way of exposing data to sysfs. However, it could also be
used in the future to allocate and release performance domains in a more
dynamic way using reference counting.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
include/linux/energy_model.h | 2 +
kernel/power/energy_model.c | 90 ++++++++++++++++++++++++++++++++++++
2 files changed, 92 insertions(+)
diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index aa027f7bcb3e..55deab2b38dc 100644
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -27,6 +27,7 @@ struct em_cap_state {
* em_perf_domain - Performance domain
* @table: List of capacity states, in ascending order
* @nr_cap_states: Number of capacity states
+ * @kobj: Kobject used to expose the domain in sysfs
* @cpus: Cpumask covering the CPUs of the domain
*
* A "performance domain" represents a group of CPUs whose performance is
@@ -37,6 +38,7 @@ struct em_cap_state {
struct em_perf_domain {
struct em_cap_state *table;
int nr_cap_states;
+ struct kobject kobj;
unsigned long cpus[0];
};
diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index d9dc2c38764a..5ec376d4f2f3 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -23,6 +23,82 @@ static DEFINE_PER_CPU(struct em_perf_domain *, em_data);
*/
static DEFINE_MUTEX(em_pd_mutex);
+static struct kobject *em_kobject;
+
+/* Getters for the attributes of em_perf_domain objects */
+struct em_pd_attr {
+ struct attribute attr;
+ ssize_t (*show)(struct em_perf_domain *pd, char *buf);
+ ssize_t (*store)(struct em_perf_domain *pd, const char *buf, size_t s);
+};
+
+#define EM_ATTR_LEN 13
+#define show_table_attr(_attr) \
+static ssize_t show_##_attr(struct em_perf_domain *pd, char *buf) \
+{ \
+ ssize_t cnt = 0; \
+ int i; \
+ for (i = 0; i < pd->nr_cap_states; i++) { \
+ if (cnt >= (ssize_t) (PAGE_SIZE / sizeof(char) \
+ - (EM_ATTR_LEN + 2))) \
+ goto out; \
+ cnt += scnprintf(&buf[cnt], EM_ATTR_LEN + 1, "%lu ", \
+ pd->table[i]._attr); \
+ } \
+out: \
+ cnt += sprintf(&buf[cnt], "\n"); \
+ return cnt; \
+}
+
+show_table_attr(power);
+show_table_attr(frequency);
+show_table_attr(cost);
+
+static ssize_t show_cpus(struct em_perf_domain *pd, char *buf)
+{
+ return sprintf(buf, "%*pbl\n", cpumask_pr_args(to_cpumask(pd->cpus)));
+}
+
+#define pd_attr(_name) em_pd_##_name##_attr
+#define define_pd_attr(_name) static struct em_pd_attr pd_attr(_name) = \
+ __ATTR(_name, 0444, show_##_name, NULL)
+
+define_pd_attr(power);
+define_pd_attr(frequency);
+define_pd_attr(cost);
+define_pd_attr(cpus);
+
+static struct attribute *em_pd_default_attrs[] = {
+ &pd_attr(power).attr,
+ &pd_attr(frequency).attr,
+ &pd_attr(cost).attr,
+ &pd_attr(cpus).attr,
+ NULL
+};
+
+#define to_pd(k) container_of(k, struct em_perf_domain, kobj)
+#define to_pd_attr(a) container_of(a, struct em_pd_attr, attr)
+
+static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
+{
+ struct em_perf_domain *pd = to_pd(kobj);
+ struct em_pd_attr *pd_attr = to_pd_attr(attr);
+ ssize_t ret;
+
+ ret = pd_attr->show(pd, buf);
+
+ return ret;
+}
+
+static const struct sysfs_ops em_pd_sysfs_ops = {
+ .show = show,
+};
+
+static struct kobj_type ktype_em_pd = {
+ .sysfs_ops = &em_pd_sysfs_ops,
+ .default_attrs = em_pd_default_attrs,
+};
+
static struct em_perf_domain *em_create_pd(cpumask_t *span, int nr_states,
struct em_data_callback *cb)
{
@@ -102,6 +178,11 @@ static struct em_perf_domain *em_create_pd(cpumask_t *span, int nr_states,
pd->nr_cap_states = nr_states;
cpumask_copy(to_cpumask(pd->cpus), span);
+ ret = kobject_init_and_add(&pd->kobj, &ktype_em_pd, em_kobject,
+ "pd%u", cpu);
+ if (ret)
+ pr_err("pd%d: failed kobject_init_and_add(): %d\n", cpu, ret);
+
return pd;
free_cs_table:
@@ -155,6 +236,15 @@ int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
*/
mutex_lock(&em_pd_mutex);
+ if (!em_kobject) {
+ em_kobject = kobject_create_and_add("energy_model",
+ &cpu_subsys.dev_root->kobj);
+ if (!em_kobject) {
+ ret = -ENODEV;
+ goto unlock;
+ }
+ }
+
for_each_cpu(cpu, span) {
/* Make sure we don't register again an existing domain. */
if (READ_ONCE(per_cpu(em_data, cpu))) {
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 05/15] sched/topology: Reference the Energy Model of CPUs when available
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (3 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 04/15] PM / EM: Expose the Energy Model in sysfs Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 06/15] sched/topology: Lowest CPU asymmetry sched_domain level pointer Quentin Perret
` (9 subsequent siblings)
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
The existing scheduling domain hierarchy is defined to map to the cache
topology of the system. However, Energy Aware Scheduling (EAS) requires
more knowledge about the platform, and specifically needs to know about
the span of Performance Domains (PD), which do not always align with
caches.
To address this issue, use the Energy Model (EM) of the system to extend
the scheduler topology code with a representation of the PDs, alongside
the scheduling domains. More specifically, a linked list of PDs is
attached to each root domain. When multiple root domains are in use,
each list contains only the PDs covering the CPUs of its root domain. If
a PD spans over CPUs of multiple different root domains, it will be
duplicated in all lists.
The lists are fully maintained by the scheduler from
partition_sched_domains() in order to cope with hotplug and cpuset
changes. As for scheduling domains, the list are protected by RCU to
ensure safe concurrent updates.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
kernel/sched/sched.h | 21 +++++++
kernel/sched/topology.c | 134 ++++++++++++++++++++++++++++++++++++++--
2 files changed, 151 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 9d28d66dd707..735302641c8b 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -44,6 +44,7 @@
#include <linux/ctype.h>
#include <linux/debugfs.h>
#include <linux/delayacct.h>
+#include <linux/energy_model.h>
#include <linux/init_task.h>
#include <linux/kprobes.h>
#include <linux/kthread.h>
@@ -708,6 +709,12 @@ static inline bool sched_asym_prefer(int a, int b)
return arch_asym_cpu_priority(a) > arch_asym_cpu_priority(b);
}
+struct perf_domain {
+ struct em_perf_domain *em_pd;
+ struct perf_domain *next;
+ struct rcu_head rcu;
+};
+
/*
* We add the notion of a root-domain which will be used to define per-domain
* variables. Each exclusive cpuset essentially defines an island domain by
@@ -760,6 +767,12 @@ struct root_domain {
struct cpupri cpupri;
unsigned long max_cpu_capacity;
+
+ /*
+ * NULL-terminated list of performance domains intersecting with the
+ * CPUs of the rd. Protected by RCU.
+ */
+ struct perf_domain *pd;
};
extern struct root_domain def_root_domain;
@@ -2278,3 +2291,11 @@ unsigned long scale_irq_capacity(unsigned long util, unsigned long irq, unsigned
return util;
}
#endif
+
+#ifdef CONFIG_SMP
+#ifdef CONFIG_ENERGY_MODEL
+#define perf_domain_span(pd) (to_cpumask(((pd)->em_pd->cpus)))
+#else
+#define perf_domain_span(pd) NULL
+#endif
+#endif
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 8d7f15ba5916..649d4aad4002 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -201,6 +201,116 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
return 1;
}
+#ifdef CONFIG_ENERGY_MODEL
+static void free_pd(struct perf_domain *pd)
+{
+ struct perf_domain *tmp;
+
+ while (pd) {
+ tmp = pd->next;
+ kfree(pd);
+ pd = tmp;
+ }
+}
+
+static struct perf_domain *find_pd(struct perf_domain *pd, int cpu)
+{
+ while (pd) {
+ if (cpumask_test_cpu(cpu, perf_domain_span(pd)))
+ return pd;
+ pd = pd->next;
+ }
+
+ return NULL;
+}
+
+static struct perf_domain *pd_init(int cpu)
+{
+ struct em_perf_domain *obj = em_cpu_get(cpu);
+ struct perf_domain *pd;
+
+ if (!obj) {
+ if (sched_debug())
+ pr_info("%s: no EM found for CPU%d\n", __func__, cpu);
+ return NULL;
+ }
+
+ pd = kzalloc(sizeof(*pd), GFP_KERNEL);
+ if (!pd)
+ return NULL;
+ pd->em_pd = obj;
+
+ return pd;
+}
+
+static void perf_domain_debug(const struct cpumask *cpu_map,
+ struct perf_domain *pd)
+{
+ if (!sched_debug() || !pd)
+ return;
+
+ printk(KERN_DEBUG "root_domain %*pbl:", cpumask_pr_args(cpu_map));
+
+ while (pd) {
+ printk(KERN_CONT " pd%d:{ cpus=%*pbl nr_cstate=%d }",
+ cpumask_first(perf_domain_span(pd)),
+ cpumask_pr_args(perf_domain_span(pd)),
+ em_pd_nr_cap_states(pd->em_pd));
+ pd = pd->next;
+ }
+
+ printk(KERN_CONT "\n");
+}
+
+static void destroy_perf_domain_rcu(struct rcu_head *rp)
+{
+ struct perf_domain *pd;
+
+ pd = container_of(rp, struct perf_domain, rcu);
+ free_pd(pd);
+}
+
+static void build_perf_domains(const struct cpumask *cpu_map)
+{
+ struct perf_domain *pd = NULL, *tmp;
+ int cpu = cpumask_first(cpu_map);
+ struct root_domain *rd = cpu_rq(cpu)->rd;
+ int i;
+
+ for_each_cpu(i, cpu_map) {
+ /* Skip already covered CPUs. */
+ if (find_pd(pd, i))
+ continue;
+
+ /* Create the new pd and add it to the local list. */
+ tmp = pd_init(i);
+ if (!tmp)
+ goto free;
+ tmp->next = pd;
+ pd = tmp;
+ }
+
+ perf_domain_debug(cpu_map, pd);
+
+ /* Attach the new list of performance domains to the root domain. */
+ tmp = rd->pd;
+ rcu_assign_pointer(rd->pd, pd);
+ if (tmp)
+ call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
+
+ return;
+
+free:
+ free_pd(pd);
+ tmp = rd->pd;
+ rcu_assign_pointer(rd->pd, NULL);
+ if (tmp)
+ call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
+}
+#else
+static void free_pd(struct perf_domain *pd) { }
+#endif /* CONFIG_ENERGY_MODEL */
+
static void free_rootdomain(struct rcu_head *rcu)
{
struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
@@ -211,6 +321,7 @@ static void free_rootdomain(struct rcu_head *rcu)
free_cpumask_var(rd->rto_mask);
free_cpumask_var(rd->online);
free_cpumask_var(rd->span);
+ free_pd(rd->pd);
kfree(rd);
}
@@ -1961,8 +2072,8 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
/* Destroy deleted domains: */
for (i = 0; i < ndoms_cur; i++) {
for (j = 0; j < n && !new_topology; j++) {
- if (cpumask_equal(doms_cur[i], doms_new[j])
- && dattrs_equal(dattr_cur, i, dattr_new, j))
+ if (cpumask_equal(doms_cur[i], doms_new[j]) &&
+ dattrs_equal(dattr_cur, i, dattr_new, j))
goto match1;
}
/* No match - a current sched domain not in new doms_new[] */
@@ -1982,8 +2093,8 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
/* Build new domains: */
for (i = 0; i < ndoms_new; i++) {
for (j = 0; j < n && !new_topology; j++) {
- if (cpumask_equal(doms_new[i], doms_cur[j])
- && dattrs_equal(dattr_new, i, dattr_cur, j))
+ if (cpumask_equal(doms_new[i], doms_cur[j]) &&
+ dattrs_equal(dattr_new, i, dattr_cur, j))
goto match2;
}
/* No match - add a new doms_new */
@@ -1992,6 +2103,21 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
;
}
+#ifdef CONFIG_ENERGY_MODEL
+ /* Build perf. domains: */
+ for (i = 0; i < ndoms_new; i++) {
+ for (j = 0; j < n; j++) {
+ if (cpumask_equal(doms_new[i], doms_cur[j]) &&
+ cpu_rq(cpumask_first(doms_cur[j]))->rd->pd)
+ goto match3;
+ }
+ /* No match - add perf. domains for a new rd */
+ build_perf_domains(doms_new[i]);
+match3:
+ ;
+ }
+#endif
+
/* Remember the new sched domains: */
if (doms_cur != &fallback_doms)
free_sched_domains(doms_cur, ndoms_cur);
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 06/15] sched/topology: Lowest CPU asymmetry sched_domain level pointer
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (4 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 05/15] sched/topology: Reference the Energy Model of CPUs when available Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 07/15] sched/topology: Disable EAS on inappropriate platforms Quentin Perret
` (8 subsequent siblings)
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
Add another member to the family of per-cpu sched_domain shortcut
pointers. This one, sd_asym_cpucapacity, points to the lowest level
at which the SD_ASYM_CPUCAPACITY flag is set. While at it, rename the
sd_asym shortcut to sd_asym_packing to avoid confusions.
Generally speaking, the largest opportunity to save energy via
scheduling comes from a smarter exploitation of heterogeneous platforms
(i.e. big.LITTLE). Consequently, the sd_asym_cpucapacity shortcut will
be used at first as the lowest domain where Energy-Aware Scheduling
(EAS) should be applied. For example, it is possible to apply EAS within
a socket on a multi-socket system, as long as each socket has an
asymmetric topology. Energy-aware cross-sockets wake-up balancing will
only happen when the system is over-utilized, or this_cpu and prev_cpu
are in different sockets.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
kernel/sched/fair.c | 2 +-
kernel/sched/sched.h | 3 ++-
kernel/sched/topology.c | 8 ++++++--
3 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e30dea59d215..6c42f3e075b9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9299,7 +9299,7 @@ static void nohz_balancer_kick(struct rq *rq)
}
}
- sd = rcu_dereference(per_cpu(sd_asym, cpu));
+ sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
if (sd) {
for_each_cpu(i, sched_domain_span(sd)) {
if (i == cpu ||
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 735302641c8b..c6e32d4684bc 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1305,7 +1305,8 @@ DECLARE_PER_CPU(int, sd_llc_size);
DECLARE_PER_CPU(int, sd_llc_id);
DECLARE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);
DECLARE_PER_CPU(struct sched_domain *, sd_numa);
-DECLARE_PER_CPU(struct sched_domain *, sd_asym);
+DECLARE_PER_CPU(struct sched_domain *, sd_asym_packing);
+DECLARE_PER_CPU(struct sched_domain *, sd_asym_cpucapacity);
extern struct static_key_false sched_asym_cpucapacity;
struct sched_group_capacity {
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 649d4aad4002..76ff03f51fa9 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -508,7 +508,8 @@ DEFINE_PER_CPU(int, sd_llc_size);
DEFINE_PER_CPU(int, sd_llc_id);
DEFINE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);
DEFINE_PER_CPU(struct sched_domain *, sd_numa);
-DEFINE_PER_CPU(struct sched_domain *, sd_asym);
+DEFINE_PER_CPU(struct sched_domain *, sd_asym_packing);
+DEFINE_PER_CPU(struct sched_domain *, sd_asym_cpucapacity);
DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity);
static void update_top_cache_domain(int cpu)
@@ -534,7 +535,10 @@ static void update_top_cache_domain(int cpu)
rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
- rcu_assign_pointer(per_cpu(sd_asym, cpu), sd);
+ rcu_assign_pointer(per_cpu(sd_asym_packing, cpu), sd);
+
+ sd = lowest_flag_domain(cpu, SD_ASYM_CPUCAPACITY);
+ rcu_assign_pointer(per_cpu(sd_asym_cpucapacity, cpu), sd);
}
/*
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 07/15] sched/topology: Disable EAS on inappropriate platforms
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (5 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 06/15] sched/topology: Lowest CPU asymmetry sched_domain level pointer Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 08/15] sched/topology: Make Energy Aware Scheduling depend on schedutil Quentin Perret
` (7 subsequent siblings)
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
Energy Aware Scheduling (EAS) in its current form is most relevant on
platforms with asymmetric CPU topologies (e.g. Arm big.LITTLE) since
this is where there is a lot of potential for saving energy through
scheduling. This is particularly true since the Energy Model only
includes the active power costs of CPUs, hence not providing enough data
to compare packing-vs-spreading strategies.
As such, disable EAS on root domains where the SD_ASYM_CPUCAPACITY flag
is not set. While at it, disable EAS on systems where the complexity of
the Energy Model is too high since that could lead to unacceptable
scheduling overhead.
All in all, EAS can be used on a root domain if and only if:
1. an Energy Model is available;
2. the root domain has an asymmetric CPU capacity topology;
3. the complexity of the root domain's EM is low enough to keep
scheduling overheads low.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
kernel/sched/topology.c | 49 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 48 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 76ff03f51fa9..992a2a893df1 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -270,12 +270,45 @@ static void destroy_perf_domain_rcu(struct rcu_head *rp)
free_pd(pd);
}
+/*
+ * EAS can be used on a root domain if it meets all the following conditions:
+ * 1. an Energy Model (EM) is available;
+ * 2. the SD_ASYM_CPUCAPACITY flag is set in the sched_domain hierarchy.
+ * 3. the EM complexity is low enough to keep scheduling overheads low;
+ *
+ * The complexity of the Energy Model is defined as:
+ *
+ * C = nr_pd * (nr_cpus + nr_cs)
+ *
+ * with parameters defined as:
+ * - nr_pd: the number of performance domains
+ * - nr_cpus: the number of CPUs
+ * - nr_cs: the sum of the number of capacity states of all performance
+ * domains (for example, on a system with 2 performance domains,
+ * with 10 capacity states each, nr_cs = 2 * 10 = 20).
+ *
+ * It is generally not a good idea to use such a model in the wake-up path on
+ * very complex platforms because of the associated scheduling overheads. The
+ * arbitrary constraint below prevents that. It makes EAS usable up to 16 CPUs
+ * with per-CPU DVFS and less than 8 capacity states each, for example.
+ */
+#define EM_MAX_COMPLEXITY 2048
+
static void build_perf_domains(const struct cpumask *cpu_map)
{
+ int i, nr_pd = 0, nr_cs = 0, nr_cpus = cpumask_weight(cpu_map);
struct perf_domain *pd = NULL, *tmp;
int cpu = cpumask_first(cpu_map);
struct root_domain *rd = cpu_rq(cpu)->rd;
- int i;
+
+ /* EAS is enabled for asymmetric CPU capacity topologies. */
+ if (!per_cpu(sd_asym_cpucapacity, cpu)) {
+ if (sched_debug()) {
+ pr_info("rd %*pbl: CPUs do not have asymmetric capacities\n",
+ cpumask_pr_args(cpu_map));
+ }
+ goto free;
+ }
for_each_cpu(i, cpu_map) {
/* Skip already covered CPUs. */
@@ -288,6 +321,20 @@ static void build_perf_domains(const struct cpumask *cpu_map)
goto free;
tmp->next = pd;
pd = tmp;
+
+ /*
+ * Count performance domains and capacity states for the
+ * complexity check.
+ */
+ nr_pd++;
+ nr_cs += em_pd_nr_cap_states(pd->em_pd);
+ }
+
+ /* Bail out if the Energy Model complexity is too high. */
+ if (nr_pd * (nr_cs + nr_cpus) > EM_MAX_COMPLEXITY) {
+ WARN(1, "rd %*pbl: Failed to start EAS, EM complexity is too high\n",
+ cpumask_pr_args(cpu_map));
+ goto free;
}
perf_domain_debug(cpu_map, pd);
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 08/15] sched/topology: Make Energy Aware Scheduling depend on schedutil
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (6 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 07/15] sched/topology: Disable EAS on inappropriate platforms Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-22 14:04 ` Peter Zijlstra
2018-11-19 14:18 ` [PATCH v9 09/15] sched: Introduce sched_energy_present static key Quentin Perret
` (6 subsequent siblings)
14 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
Energy Aware Scheduling (EAS) is designed with the assumption that
frequencies of CPUs follow their utilization value. When using a CPUFreq
governor other than schedutil, the chances of this assumption being true
are small, if any. When schedutil is being used, EAS' predictions are at
least consistent with the frequency requests. Although those requests
have no guarantees to be honored by the hardware, they should at least
guide DVFS in the right direction and provide some hope in regards to the
EAS model being accurate.
To make sure EAS is only used in a sane configuration, create a strong
dependency on schedutil being used. Since having sugov compiled-in does
not provide that guarantee, make CPUFreq call a scheduler function on
governor changes hence letting it rebuild the scheduling domains, check
the governors of the online CPUs, and enable/disable EAS accordingly.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
drivers/cpufreq/cpufreq.c | 2 ++
include/linux/sched/cpufreq.h | 9 ++++++++
kernel/sched/cpufreq_schedutil.c | 37 ++++++++++++++++++++++++++++++--
kernel/sched/sched.h | 4 +---
kernel/sched/topology.c | 28 ++++++++++++++++++++----
5 files changed, 71 insertions(+), 9 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 7aa3dcad2175..42da820a3ccb 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -25,6 +25,7 @@
#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/mutex.h>
+#include <linux/sched/cpufreq.h>
#include <linux/slab.h>
#include <linux/suspend.h>
#include <linux/syscore_ops.h>
@@ -2277,6 +2278,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
ret = cpufreq_start_governor(policy);
if (!ret) {
pr_debug("cpufreq: governor change\n");
+ sched_cpufreq_governor_change(policy, old_gov);
return 0;
}
cpufreq_exit_governor(policy);
diff --git a/include/linux/sched/cpufreq.h b/include/linux/sched/cpufreq.h
index afa940cd50dc..a2ead52feb17 100644
--- a/include/linux/sched/cpufreq.h
+++ b/include/linux/sched/cpufreq.h
@@ -2,6 +2,7 @@
#ifndef _LINUX_SCHED_CPUFREQ_H
#define _LINUX_SCHED_CPUFREQ_H
+#include <linux/cpufreq.h>
#include <linux/types.h>
/*
@@ -28,4 +29,12 @@ static inline unsigned long map_util_freq(unsigned long util,
}
#endif /* CONFIG_CPU_FREQ */
+#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
+void sched_cpufreq_governor_change(struct cpufreq_policy *policy,
+ struct cpufreq_governor *old_gov);
+#else
+static inline void sched_cpufreq_governor_change(struct cpufreq_policy *policy,
+ struct cpufreq_governor *old_gov) { }
+#endif
+
#endif /* _LINUX_SCHED_CPUFREQ_H */
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 105cf70fcb69..804eb7ae944a 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -631,7 +631,7 @@ static struct kobj_type sugov_tunables_ktype = {
/********************** cpufreq governor interface *********************/
-static struct cpufreq_governor schedutil_gov;
+struct cpufreq_governor schedutil_gov;
static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
{
@@ -890,7 +890,7 @@ static void sugov_limits(struct cpufreq_policy *policy)
sg_policy->need_freq_update = true;
}
-static struct cpufreq_governor schedutil_gov = {
+struct cpufreq_governor schedutil_gov = {
.name = "schedutil",
.owner = THIS_MODULE,
.dynamic_switching = true,
@@ -913,3 +913,36 @@ static int __init sugov_register(void)
return cpufreq_register_governor(&schedutil_gov);
}
fs_initcall(sugov_register);
+
+#ifdef CONFIG_ENERGY_MODEL
+extern bool sched_energy_update;
+extern struct mutex sched_energy_mutex;
+
+static void rebuild_sd_workfn(struct work_struct *work)
+{
+ mutex_lock(&sched_energy_mutex);
+ sched_energy_update = true;
+ rebuild_sched_domains();
+ sched_energy_update = false;
+ mutex_unlock(&sched_energy_mutex);
+}
+static DECLARE_WORK(rebuild_sd_work, rebuild_sd_workfn);
+
+/*
+ * EAS shouldn't be attempted without sugov, so rebuild the sched_domains
+ * on governor changes to make sure the scheduler knows about it.
+ */
+void sched_cpufreq_governor_change(struct cpufreq_policy *policy,
+ struct cpufreq_governor *old_gov)
+{
+ if (old_gov == &schedutil_gov || policy->governor == &schedutil_gov) {
+ /*
+ * When called from the cpufreq_register_driver() path, the
+ * cpu_hotplug_lock is already held, so use a work item to
+ * avoid nested locking in rebuild_sched_domains().
+ */
+ schedule_work(&rebuild_sd_work);
+ }
+
+}
+#endif
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c6e32d4684bc..0278b251c379 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2293,10 +2293,8 @@ unsigned long scale_irq_capacity(unsigned long util, unsigned long irq, unsigned
}
#endif
-#ifdef CONFIG_SMP
-#ifdef CONFIG_ENERGY_MODEL
+#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
#define perf_domain_span(pd) (to_cpumask(((pd)->em_pd->cpus)))
#else
#define perf_domain_span(pd) NULL
#endif
-#endif
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 992a2a893df1..70492d4bfed6 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -201,7 +201,10 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
return 1;
}
-#ifdef CONFIG_ENERGY_MODEL
+#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
+DEFINE_MUTEX(sched_energy_mutex);
+bool sched_energy_update;
+
static void free_pd(struct perf_domain *pd)
{
struct perf_domain *tmp;
@@ -275,6 +278,7 @@ static void destroy_perf_domain_rcu(struct rcu_head *rp)
* 1. an Energy Model (EM) is available;
* 2. the SD_ASYM_CPUCAPACITY flag is set in the sched_domain hierarchy.
* 3. the EM complexity is low enough to keep scheduling overheads low;
+ * 4. schedutil is driving the frequency of all CPUs of the rd;
*
* The complexity of the Energy Model is defined as:
*
@@ -294,12 +298,15 @@ static void destroy_perf_domain_rcu(struct rcu_head *rp)
*/
#define EM_MAX_COMPLEXITY 2048
+extern struct cpufreq_governor schedutil_gov;
static void build_perf_domains(const struct cpumask *cpu_map)
{
int i, nr_pd = 0, nr_cs = 0, nr_cpus = cpumask_weight(cpu_map);
struct perf_domain *pd = NULL, *tmp;
int cpu = cpumask_first(cpu_map);
struct root_domain *rd = cpu_rq(cpu)->rd;
+ struct cpufreq_policy *policy;
+ struct cpufreq_governor *gov;
/* EAS is enabled for asymmetric CPU capacity topologies. */
if (!per_cpu(sd_asym_cpucapacity, cpu)) {
@@ -315,6 +322,19 @@ static void build_perf_domains(const struct cpumask *cpu_map)
if (find_pd(pd, i))
continue;
+ /* Do not attempt EAS if schedutil is not being used. */
+ policy = cpufreq_cpu_get(i);
+ if (!policy)
+ goto free;
+ gov = policy->governor;
+ cpufreq_cpu_put(policy);
+ if (gov != &schedutil_gov) {
+ if (rd->pd)
+ pr_warn("rd %*pbl: Disabling EAS, schedutil is mandatory\n",
+ cpumask_pr_args(cpu_map));
+ goto free;
+ }
+
/* Create the new pd and add it to the local list. */
tmp = pd_init(i);
if (!tmp)
@@ -356,7 +376,7 @@ static void build_perf_domains(const struct cpumask *cpu_map)
}
#else
static void free_pd(struct perf_domain *pd) { }
-#endif /* CONFIG_ENERGY_MODEL */
+#endif /* CONFIG_ENERGY_MODEL && CONFIG_CPU_FREQ_GOV_SCHEDUTIL*/
static void free_rootdomain(struct rcu_head *rcu)
{
@@ -2154,10 +2174,10 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
;
}
-#ifdef CONFIG_ENERGY_MODEL
+#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
/* Build perf. domains: */
for (i = 0; i < ndoms_new; i++) {
- for (j = 0; j < n; j++) {
+ for (j = 0; j < n && !sched_energy_update; j++) {
if (cpumask_equal(doms_new[i], doms_cur[j]) &&
cpu_rq(cpumask_first(doms_cur[j]))->rd->pd)
goto match3;
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* Re: [PATCH v9 08/15] sched/topology: Make Energy Aware Scheduling depend on schedutil
2018-11-19 14:18 ` [PATCH v9 08/15] sched/topology: Make Energy Aware Scheduling depend on schedutil Quentin Perret
@ 2018-11-22 14:04 ` Peter Zijlstra
2018-11-22 15:49 ` Rafael J. Wysocki
0 siblings, 1 reply; 35+ messages in thread
From: Peter Zijlstra @ 2018-11-22 14:04 UTC (permalink / raw)
To: Quentin Perret
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Mon, Nov 19, 2018 at 02:18:50PM +0000, Quentin Perret wrote:
> + if (rd->pd)
> + pr_warn("rd %*pbl: Disabling EAS, schedutil is mandatory\n",
> + cpumask_pr_args(cpu_map));
> + goto free;
I would have preferred just not allowing the governor to change at all,
but if you want to allow that, this is, I suppose, the best you can do.
Rafael, are you otherwise OK with the grubbing inside cpufreq?
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 08/15] sched/topology: Make Energy Aware Scheduling depend on schedutil
2018-11-22 14:04 ` Peter Zijlstra
@ 2018-11-22 15:49 ` Rafael J. Wysocki
2018-11-22 15:56 ` Quentin Perret
0 siblings, 1 reply; 35+ messages in thread
From: Rafael J. Wysocki @ 2018-11-22 15:49 UTC (permalink / raw)
To: Peter Zijlstra, Quentin Perret
Cc: Rafael J. Wysocki, Linux Kernel Mailing List, Linux PM,
Greg Kroah-Hartman, Ingo Molnar, Dietmar Eggemann,
Morten Rasmussen, Chris Redpath, Patrick Bellasi,
Valentin Schneider, Vincent Guittot, Thara Gopinath,
Viresh Kumar, Todd Kjos, Joel Fernandes, Steve Muckle, adharmap,
Saravana Kannan, Pavan Kondeti, Juri Lelli, Eduardo Valentin,
Srinivas Pandruvada, currojerez, Javi Merino
On Thu, Nov 22, 2018 at 3:05 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Mon, Nov 19, 2018 at 02:18:50PM +0000, Quentin Perret wrote:
> > + if (rd->pd)
> > + pr_warn("rd %*pbl: Disabling EAS, schedutil is mandatory\n",
> > + cpumask_pr_args(cpu_map));
> > + goto free;
>
> I would have preferred just not allowing the governor to change at all,
> but if you want to allow that, this is, I suppose, the best you can do.
>
> Rafael, are you otherwise OK with the grubbing inside cpufreq?
Sort of. :-)
I would put the sched_cpufreq_governor_change() header (and the static
inline stub of it) into linux/cpufreq.h (instead of
linux/sched/cpufreq.h) so that cpufreq.c doesn't have to include
linux/sched/cpufreq.h which is kind of confusing.
Apart from that the changes are fine by me.
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 08/15] sched/topology: Make Energy Aware Scheduling depend on schedutil
2018-11-22 15:49 ` Rafael J. Wysocki
@ 2018-11-22 15:56 ` Quentin Perret
0 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-22 15:56 UTC (permalink / raw)
To: Rafael J. Wysocki
Cc: Peter Zijlstra, Rafael J. Wysocki, Linux Kernel Mailing List,
Linux PM, Greg Kroah-Hartman, Ingo Molnar, Dietmar Eggemann,
Morten Rasmussen, Chris Redpath, Patrick Bellasi,
Valentin Schneider, Vincent Guittot, Thara Gopinath,
Viresh Kumar, Todd Kjos, Joel Fernandes, Steve Muckle, adharmap,
Saravana Kannan, Pavan Kondeti, Juri Lelli, Eduardo Valentin,
Srinivas Pandruvada, currojerez, Javi Merino
On Thursday 22 Nov 2018 at 16:49:04 (+0100), Rafael J. Wysocki wrote:
> On Thu, Nov 22, 2018 at 3:05 PM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Mon, Nov 19, 2018 at 02:18:50PM +0000, Quentin Perret wrote:
> > > + if (rd->pd)
> > > + pr_warn("rd %*pbl: Disabling EAS, schedutil is mandatory\n",
> > > + cpumask_pr_args(cpu_map));
> > > + goto free;
> >
> > I would have preferred just not allowing the governor to change at all,
> > but if you want to allow that, this is, I suppose, the best you can do.
> >
> > Rafael, are you otherwise OK with the grubbing inside cpufreq?
>
> Sort of. :-)
>
> I would put the sched_cpufreq_governor_change() header (and the static
> inline stub of it) into linux/cpufreq.h (instead of
> linux/sched/cpufreq.h) so that cpufreq.c doesn't have to include
> linux/sched/cpufreq.h which is kind of confusing.
That works for me.
Thanks,
Quentin
^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH v9 09/15] sched: Introduce sched_energy_present static key
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (7 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 08/15] sched/topology: Make Energy Aware Scheduling depend on schedutil Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-21 13:08 ` Peter Zijlstra
2018-11-19 14:18 ` [PATCH v9 10/15] sched: Introduce a sysctl for Energy Aware Scheduling Quentin Perret
` (5 subsequent siblings)
14 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
In order to make sure Energy Aware Scheduling (EAS) will not impact
systems where no Energy Model is available, introduce a static key
guarding the access to EAS code. Since EAS is enabled on a
per-root-domain basis, the static key is enabled when at least one root
domain meets all conditions for EAS.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
kernel/sched/sched.h | 4 ++++
kernel/sched/topology.c | 31 +++++++++++++++++++++++++++++++
2 files changed, 35 insertions(+)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 0278b251c379..5b636a8aa900 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2298,3 +2298,7 @@ unsigned long scale_irq_capacity(unsigned long util, unsigned long irq, unsigned
#else
#define perf_domain_span(pd) NULL
#endif
+
+#ifdef CONFIG_SMP
+extern struct static_key_false sched_energy_present;
+#endif
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 70492d4bfed6..1457ef80ee94 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -201,6 +201,7 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
return 1;
}
+DEFINE_STATIC_KEY_FALSE(sched_energy_present);
#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
DEFINE_MUTEX(sched_energy_mutex);
bool sched_energy_update;
@@ -273,6 +274,35 @@ static void destroy_perf_domain_rcu(struct rcu_head *rp)
free_pd(pd);
}
+static void sched_energy_start(int ndoms_new, cpumask_var_t doms_new[])
+{
+ /*
+ * The conditions for EAS to start are checked during the creation of
+ * root domains. If one of them meets all conditions, it will have a
+ * non-null list of performance domains.
+ */
+ while (ndoms_new) {
+ if (cpu_rq(cpumask_first(doms_new[ndoms_new - 1]))->rd->pd)
+ goto enable;
+ ndoms_new--;
+ }
+
+ if (static_branch_unlikely(&sched_energy_present)) {
+ if (sched_debug())
+ pr_info("%s: stopping EAS\n", __func__);
+ static_branch_disable_cpuslocked(&sched_energy_present);
+ }
+
+ return;
+
+enable:
+ if (!static_branch_unlikely(&sched_energy_present)) {
+ if (sched_debug())
+ pr_info("%s: starting EAS\n", __func__);
+ static_branch_enable_cpuslocked(&sched_energy_present);
+ }
+}
+
/*
* EAS can be used on a root domain if it meets all the following conditions:
* 1. an Energy Model (EM) is available;
@@ -2187,6 +2217,7 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
match3:
;
}
+ sched_energy_start(ndoms_new, doms_new);
#endif
/* Remember the new sched domains: */
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* Re: [PATCH v9 09/15] sched: Introduce sched_energy_present static key
2018-11-19 14:18 ` [PATCH v9 09/15] sched: Introduce sched_energy_present static key Quentin Perret
@ 2018-11-21 13:08 ` Peter Zijlstra
2018-11-21 15:14 ` Quentin Perret
0 siblings, 1 reply; 35+ messages in thread
From: Peter Zijlstra @ 2018-11-21 13:08 UTC (permalink / raw)
To: Quentin Perret
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Mon, Nov 19, 2018 at 02:18:51PM +0000, Quentin Perret wrote:
> +static void sched_energy_start(int ndoms_new, cpumask_var_t doms_new[])
> +{
> + /*
> + * The conditions for EAS to start are checked during the creation of
> + * root domains. If one of them meets all conditions, it will have a
> + * non-null list of performance domains.
> + */
> + while (ndoms_new) {
> + if (cpu_rq(cpumask_first(doms_new[ndoms_new - 1]))->rd->pd)
> + goto enable;
> + ndoms_new--;
> + }
That seems quite ugly; can't you simply return a bool from
build_perf_domains() ?
Something like the below, but less fugly ;-)
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -299,7 +299,7 @@ static void destroy_perf_domain_rcu(stru
#define EM_MAX_COMPLEXITY 2048
extern struct cpufreq_governor schedutil_gov;
-static void build_perf_domains(const struct cpumask *cpu_map)
+static bool build_perf_domains(const struct cpumask *cpu_map)
{
int i, nr_pd = 0, nr_cs = 0, nr_cpus = cpumask_weight(cpu_map);
struct perf_domain *pd = NULL, *tmp;
@@ -365,7 +365,7 @@ static void build_perf_domains(const str
if (tmp)
call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
- return;
+ return !!pd;
free:
free_pd(pd);
@@ -373,6 +373,8 @@ static void build_perf_domains(const str
rcu_assign_pointer(rd->pd, NULL);
if (tmp)
call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
+
+ return false;
}
#else
static void free_pd(struct perf_domain *pd) { }
@@ -2173,6 +2175,9 @@ void partition_sched_domains(int ndoms_n
}
#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
+ {
+ bool has_eas = false;
+
/* Build perf. domains: */
for (i = 0; i < ndoms_new; i++) {
for (j = 0; j < n && !sched_energy_update; j++) {
@@ -2181,10 +2186,13 @@ void partition_sched_domains(int ndoms_n
goto match3;
}
/* No match - add perf. domains for a new rd */
- build_perf_domains(doms_new[i]);
+ has_eas |= build_perf_domains(doms_new[i]);
match3:
;
}
+
+ sched_energy_set(has_eas);
+ }
#endif
/* Remember the new sched domains: */
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 09/15] sched: Introduce sched_energy_present static key
2018-11-21 13:08 ` Peter Zijlstra
@ 2018-11-21 15:14 ` Quentin Perret
2018-11-22 9:17 ` Quentin Perret
0 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-21 15:14 UTC (permalink / raw)
To: Peter Zijlstra
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
Hi Peter,
On Wednesday 21 Nov 2018 at 14:08:22 (+0100), Peter Zijlstra wrote:
> On Mon, Nov 19, 2018 at 02:18:51PM +0000, Quentin Perret wrote:
>
> > +static void sched_energy_start(int ndoms_new, cpumask_var_t doms_new[])
> > +{
> > + /*
> > + * The conditions for EAS to start are checked during the creation of
> > + * root domains. If one of them meets all conditions, it will have a
> > + * non-null list of performance domains.
> > + */
> > + while (ndoms_new) {
> > + if (cpu_rq(cpumask_first(doms_new[ndoms_new - 1]))->rd->pd)
> > + goto enable;
> > + ndoms_new--;
> > + }
>
> That seems quite ugly; can't you simply return a bool from
> build_perf_domains() ?
>
> Something like the below, but less fugly ;-)
>
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -299,7 +299,7 @@ static void destroy_perf_domain_rcu(stru
> #define EM_MAX_COMPLEXITY 2048
>
> extern struct cpufreq_governor schedutil_gov;
> -static void build_perf_domains(const struct cpumask *cpu_map)
> +static bool build_perf_domains(const struct cpumask *cpu_map)
> {
> int i, nr_pd = 0, nr_cs = 0, nr_cpus = cpumask_weight(cpu_map);
> struct perf_domain *pd = NULL, *tmp;
> @@ -365,7 +365,7 @@ static void build_perf_domains(const str
> if (tmp)
> call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
>
> - return;
> + return !!pd;
>
> free:
> free_pd(pd);
> @@ -373,6 +373,8 @@ static void build_perf_domains(const str
> rcu_assign_pointer(rd->pd, NULL);
> if (tmp)
> call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
> +
> + return false;
> }
> #else
> static void free_pd(struct perf_domain *pd) { }
> @@ -2173,6 +2175,9 @@ void partition_sched_domains(int ndoms_n
> }
>
> #if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
> + {
> + bool has_eas = false;
That one wants to be declared '__maybe_unused' at the top of
partition_sched_domains() perhaps ? Just to avoid the { } section.
Hopefully the compiler will be smart enough to not use stack space for
it if not needed.
> +
> /* Build perf. domains: */
> for (i = 0; i < ndoms_new; i++) {
> for (j = 0; j < n && !sched_energy_update; j++) {
> @@ -2181,10 +2186,13 @@ void partition_sched_domains(int ndoms_n
> goto match3;
And we want to do 'has_eas = true' just before 'goto match3' here.
Otherwise we'll end up disabling EAS if we hit 'goto match3' for all
root domains.
> }
> /* No match - add perf. domains for a new rd */
> - build_perf_domains(doms_new[i]);
> + has_eas |= build_perf_domains(doms_new[i]);
> match3:
> ;
> }
> +
> + sched_energy_set(has_eas);
> + }
> #endif
>
> /* Remember the new sched domains: */
Other than that I guess that should work OK :-)
Thanks,
Quentin
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 09/15] sched: Introduce sched_energy_present static key
2018-11-21 15:14 ` Quentin Perret
@ 2018-11-22 9:17 ` Quentin Perret
2018-11-22 9:32 ` Quentin Perret
0 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-22 9:17 UTC (permalink / raw)
To: Peter Zijlstra
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Wednesday 21 Nov 2018 at 15:14:45 (+0000), Quentin Perret wrote:
> Hi Peter,
>
> On Wednesday 21 Nov 2018 at 14:08:22 (+0100), Peter Zijlstra wrote:
> > On Mon, Nov 19, 2018 at 02:18:51PM +0000, Quentin Perret wrote:
> >
> > > +static void sched_energy_start(int ndoms_new, cpumask_var_t doms_new[])
> > > +{
> > > + /*
> > > + * The conditions for EAS to start are checked during the creation of
> > > + * root domains. If one of them meets all conditions, it will have a
> > > + * non-null list of performance domains.
> > > + */
> > > + while (ndoms_new) {
> > > + if (cpu_rq(cpumask_first(doms_new[ndoms_new - 1]))->rd->pd)
> > > + goto enable;
> > > + ndoms_new--;
> > > + }
> >
> > That seems quite ugly; can't you simply return a bool from
> > build_perf_domains() ?
> >
> > Something like the below, but less fugly ;-)
> >
> > --- a/kernel/sched/topology.c
> > +++ b/kernel/sched/topology.c
> > @@ -299,7 +299,7 @@ static void destroy_perf_domain_rcu(stru
> > #define EM_MAX_COMPLEXITY 2048
> >
> > extern struct cpufreq_governor schedutil_gov;
> > -static void build_perf_domains(const struct cpumask *cpu_map)
> > +static bool build_perf_domains(const struct cpumask *cpu_map)
> > {
> > int i, nr_pd = 0, nr_cs = 0, nr_cpus = cpumask_weight(cpu_map);
> > struct perf_domain *pd = NULL, *tmp;
> > @@ -365,7 +365,7 @@ static void build_perf_domains(const str
> > if (tmp)
> > call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
> >
> > - return;
> > + return !!pd;
> >
> > free:
> > free_pd(pd);
> > @@ -373,6 +373,8 @@ static void build_perf_domains(const str
> > rcu_assign_pointer(rd->pd, NULL);
> > if (tmp)
> > call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
> > +
> > + return false;
> > }
> > #else
> > static void free_pd(struct perf_domain *pd) { }
> > @@ -2173,6 +2175,9 @@ void partition_sched_domains(int ndoms_n
> > }
> >
> > #if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
> > + {
> > + bool has_eas = false;
>
> That one wants to be declared '__maybe_unused' at the top of
> partition_sched_domains() perhaps ? Just to avoid the { } section.
> Hopefully the compiler will be smart enough to not use stack space for
> it if not needed.
>
> > +
> > /* Build perf. domains: */
> > for (i = 0; i < ndoms_new; i++) {
> > for (j = 0; j < n && !sched_energy_update; j++) {
> > @@ -2181,10 +2186,13 @@ void partition_sched_domains(int ndoms_n
> > goto match3;
>
> And we want to do 'has_eas = true' just before 'goto match3' here.
> Otherwise we'll end up disabling EAS if we hit 'goto match3' for all
> root domains.
>
> > }
> > /* No match - add perf. domains for a new rd */
> > - build_perf_domains(doms_new[i]);
> > + has_eas |= build_perf_domains(doms_new[i]);
> > match3:
> > ;
> > }
> > +
> > + sched_energy_set(has_eas);
> > + }
> > #endif
> >
> > /* Remember the new sched domains: */
>
> Other than that I guess that should work OK :-)
So I actually just came across your patch that does
static_branch_{inc,dec} on sched_smt_present. Maybe I could do something
similar here ?
How about something like the below (totally untested):
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 8f9dfea60344..10ac32a0dc2e 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -298,6 +298,7 @@ static void destroy_perf_domain_rcu(struct rcu_head *rp)
pd = container_of(rp, struct perf_domain, rcu);
free_pd(pd);
+ static_branch_dec_cpuslocked(&sched_energy_present);
}
static void sched_energy_start(int ndoms_new, cpumask_var_t doms_new[])
@@ -421,6 +422,8 @@ static void build_perf_domains(const struct cpumask *cpu_map)
/* Attach the new list of performance domains to the root domain. */
tmp = rd->pd;
rcu_assign_pointer(rd->pd, pd);
+ static_branch_inc_cpuslocked(&sched_energy_present);
+
if (tmp)
call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
@@ -2246,7 +2249,6 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
match3:
;
}
- sched_energy_start(ndoms_new, doms_new);
#endif
/* Remember the new sched domains: */
^ permalink raw reply related [flat|nested] 35+ messages in thread* Re: [PATCH v9 09/15] sched: Introduce sched_energy_present static key
2018-11-22 9:17 ` Quentin Perret
@ 2018-11-22 9:32 ` Quentin Perret
2018-11-22 10:25 ` Peter Zijlstra
0 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-22 9:32 UTC (permalink / raw)
To: Peter Zijlstra
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Thursday 22 Nov 2018 at 09:17:16 (+0000), Quentin Perret wrote:
> On Wednesday 21 Nov 2018 at 15:14:45 (+0000), Quentin Perret wrote:
> > Hi Peter,
> >
> > On Wednesday 21 Nov 2018 at 14:08:22 (+0100), Peter Zijlstra wrote:
> > > On Mon, Nov 19, 2018 at 02:18:51PM +0000, Quentin Perret wrote:
> > >
> > > > +static void sched_energy_start(int ndoms_new, cpumask_var_t doms_new[])
> > > > +{
> > > > + /*
> > > > + * The conditions for EAS to start are checked during the creation of
> > > > + * root domains. If one of them meets all conditions, it will have a
> > > > + * non-null list of performance domains.
> > > > + */
> > > > + while (ndoms_new) {
> > > > + if (cpu_rq(cpumask_first(doms_new[ndoms_new - 1]))->rd->pd)
> > > > + goto enable;
> > > > + ndoms_new--;
> > > > + }
> > >
> > > That seems quite ugly; can't you simply return a bool from
> > > build_perf_domains() ?
> > >
> > > Something like the below, but less fugly ;-)
> > >
> > > --- a/kernel/sched/topology.c
> > > +++ b/kernel/sched/topology.c
> > > @@ -299,7 +299,7 @@ static void destroy_perf_domain_rcu(stru
> > > #define EM_MAX_COMPLEXITY 2048
> > >
> > > extern struct cpufreq_governor schedutil_gov;
> > > -static void build_perf_domains(const struct cpumask *cpu_map)
> > > +static bool build_perf_domains(const struct cpumask *cpu_map)
> > > {
> > > int i, nr_pd = 0, nr_cs = 0, nr_cpus = cpumask_weight(cpu_map);
> > > struct perf_domain *pd = NULL, *tmp;
> > > @@ -365,7 +365,7 @@ static void build_perf_domains(const str
> > > if (tmp)
> > > call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
> > >
> > > - return;
> > > + return !!pd;
> > >
> > > free:
> > > free_pd(pd);
> > > @@ -373,6 +373,8 @@ static void build_perf_domains(const str
> > > rcu_assign_pointer(rd->pd, NULL);
> > > if (tmp)
> > > call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
> > > +
> > > + return false;
> > > }
> > > #else
> > > static void free_pd(struct perf_domain *pd) { }
> > > @@ -2173,6 +2175,9 @@ void partition_sched_domains(int ndoms_n
> > > }
> > >
> > > #if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
> > > + {
> > > + bool has_eas = false;
> >
> > That one wants to be declared '__maybe_unused' at the top of
> > partition_sched_domains() perhaps ? Just to avoid the { } section.
> > Hopefully the compiler will be smart enough to not use stack space for
> > it if not needed.
> >
> > > +
> > > /* Build perf. domains: */
> > > for (i = 0; i < ndoms_new; i++) {
> > > for (j = 0; j < n && !sched_energy_update; j++) {
> > > @@ -2181,10 +2186,13 @@ void partition_sched_domains(int ndoms_n
> > > goto match3;
> >
> > And we want to do 'has_eas = true' just before 'goto match3' here.
> > Otherwise we'll end up disabling EAS if we hit 'goto match3' for all
> > root domains.
> >
> > > }
> > > /* No match - add perf. domains for a new rd */
> > > - build_perf_domains(doms_new[i]);
> > > + has_eas |= build_perf_domains(doms_new[i]);
> > > match3:
> > > ;
> > > }
> > > +
> > > + sched_energy_set(has_eas);
> > > + }
> > > #endif
> > >
> > > /* Remember the new sched domains: */
> >
> > Other than that I guess that should work OK :-)
>
> So I actually just came across your patch that does
> static_branch_{inc,dec} on sched_smt_present. Maybe I could do something
> similar here ?
>
> How about something like the below (totally untested):
>
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 8f9dfea60344..10ac32a0dc2e 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -298,6 +298,7 @@ static void destroy_perf_domain_rcu(struct rcu_head *rp)
>
> pd = container_of(rp, struct perf_domain, rcu);
> free_pd(pd);
> + static_branch_dec_cpuslocked(&sched_energy_present);
> }
>
> static void sched_energy_start(int ndoms_new, cpumask_var_t doms_new[])
> @@ -421,6 +422,8 @@ static void build_perf_domains(const struct cpumask *cpu_map)
> /* Attach the new list of performance domains to the root domain. */
> tmp = rd->pd;
> rcu_assign_pointer(rd->pd, pd);
> + static_branch_inc_cpuslocked(&sched_energy_present);
> +
> if (tmp)
> call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
>
> @@ -2246,7 +2249,6 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
> match3:
> ;
> }
> - sched_energy_start(ndoms_new, doms_new);
> #endif
>
> /* Remember the new sched domains: */
>
Hmm, I went too fast, that's totally broken. But there's still something
we can do with static_branch_{inc,dec} I think. I'll come back later
with a better solution.
Sorry for the noise :/
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 09/15] sched: Introduce sched_energy_present static key
2018-11-22 9:32 ` Quentin Perret
@ 2018-11-22 10:25 ` Peter Zijlstra
2018-11-22 15:25 ` Quentin Perret
0 siblings, 1 reply; 35+ messages in thread
From: Peter Zijlstra @ 2018-11-22 10:25 UTC (permalink / raw)
To: Quentin Perret
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Thu, Nov 22, 2018 at 09:32:39AM +0000, Quentin Perret wrote:
> Hmm, I went too fast, that's totally broken. But there's still something
> we can do with static_branch_{inc,dec} I think. I'll come back later
> with a better solution.
Right; if you count the rd's that have pd set, it should work-ish. Yes,
much cleaner if you can get it to work.
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 09/15] sched: Introduce sched_energy_present static key
2018-11-22 10:25 ` Peter Zijlstra
@ 2018-11-22 15:25 ` Quentin Perret
2018-11-22 15:51 ` Rafael J. Wysocki
0 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-22 15:25 UTC (permalink / raw)
To: Peter Zijlstra
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Thursday 22 Nov 2018 at 11:25:45 (+0100), Peter Zijlstra wrote:
> On Thu, Nov 22, 2018 at 09:32:39AM +0000, Quentin Perret wrote:
> > Hmm, I went too fast, that's totally broken. But there's still something
> > we can do with static_branch_{inc,dec} I think. I'll come back later
> > with a better solution.
>
> Right; if you count the rd's that have pd set, it should work-ish. Yes,
> much cleaner if you can get it to work.
So, I came up with the following code which seems to work OK. It's not
as I clean as I'd like, though. The fact that free_pd() can be called in
softirq context is annoying to manipulate the static key ...
An alternative to this work item workaround is to do static_branch_dec()
from build_perf_domains() and next to the three call sites of
free_rootdomain() in order to avoid the call_rcu() context. Not very
pretty either.
Or we can just stick with your original suggestion to carry a boolean
around.
Any preference ?
Thanks,
Quentin
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -232,7 +232,7 @@ int sched_energy_aware_handler(struct ctl_table *table, int write,
}
#endif
-static void free_pd(struct perf_domain *pd)
+static void _free_pd(struct perf_domain *pd)
{
struct perf_domain *tmp;
@@ -243,6 +243,24 @@ static void free_pd(struct perf_domain *pd)
}
}
+static void dec_sched_energy_workfn(struct work_struct *work)
+{
+ static_branch_dec(&sched_energy_present);
+}
+static DECLARE_WORK(dec_sched_energy_work, dec_sched_energy_workfn);
+
+static void free_pd(struct perf_domain *pd)
+{
+ if (pd) {
+ /*
+ * XXX: The static key can't be modified from SOFTIRQ context,
+ * so do it using a work item.
+ */
+ schedule_work(&dec_sched_energy_work);
+ _free_pd(pd);
+ }
+}
+
static struct perf_domain *find_pd(struct perf_domain *pd, int cpu)
{
while (pd) {
@@ -421,13 +410,14 @@ static void build_perf_domains(const struct cpumask *cpu_map)
/* Attach the new list of performance domains to the root domain. */
tmp = rd->pd;
rcu_assign_pointer(rd->pd, pd);
+ static_branch_inc_cpuslocked(&sched_energy_present);
if (tmp)
call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
return;
free:
- free_pd(pd);
+ _free_pd(pd);
tmp = rd->pd;
rcu_assign_pointer(rd->pd, NULL);
if (tmp)
@@ -2246,7 +2236,6 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
match3:
;
}
- sched_energy_start(ndoms_new, doms_new);
#endif
/* Remember the new sched domains: */
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 09/15] sched: Introduce sched_energy_present static key
2018-11-22 15:25 ` Quentin Perret
@ 2018-11-22 15:51 ` Rafael J. Wysocki
2018-11-22 15:55 ` Quentin Perret
0 siblings, 1 reply; 35+ messages in thread
From: Rafael J. Wysocki @ 2018-11-22 15:51 UTC (permalink / raw)
To: Quentin Perret
Cc: Peter Zijlstra, Rafael J. Wysocki, Linux Kernel Mailing List,
Linux PM, Greg Kroah-Hartman, Ingo Molnar, Dietmar Eggemann,
Morten Rasmussen, Chris Redpath, Patrick Bellasi,
Valentin Schneider, Vincent Guittot, Thara Gopinath,
Viresh Kumar, Todd Kjos, Joel Fernandes, Steve Muckle, adharmap,
Saravana Kannan, Pavan Kondeti, Juri Lelli, Eduardo Valentin,
Srinivas Pandruvada, currojerez, Javi Merino
On Thu, Nov 22, 2018 at 4:25 PM Quentin Perret <quentin.perret@arm.com> wrote:
>
> On Thursday 22 Nov 2018 at 11:25:45 (+0100), Peter Zijlstra wrote:
> > On Thu, Nov 22, 2018 at 09:32:39AM +0000, Quentin Perret wrote:
> > > Hmm, I went too fast, that's totally broken. But there's still something
> > > we can do with static_branch_{inc,dec} I think. I'll come back later
> > > with a better solution.
> >
> > Right; if you count the rd's that have pd set, it should work-ish. Yes,
> > much cleaner if you can get it to work.
>
> So, I came up with the following code which seems to work OK. It's not
> as I clean as I'd like, though. The fact that free_pd() can be called in
> softirq context is annoying to manipulate the static key ...
>
> An alternative to this work item workaround is to do static_branch_dec()
> from build_perf_domains() and next to the three call sites of
> free_rootdomain() in order to avoid the call_rcu() context. Not very
> pretty either.
>
> Or we can just stick with your original suggestion to carry a boolean
> around.
What's problematic with carrying a boolean around?
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 09/15] sched: Introduce sched_energy_present static key
2018-11-22 15:51 ` Rafael J. Wysocki
@ 2018-11-22 15:55 ` Quentin Perret
0 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-22 15:55 UTC (permalink / raw)
To: Rafael J. Wysocki
Cc: Peter Zijlstra, Rafael J. Wysocki, Linux Kernel Mailing List,
Linux PM, Greg Kroah-Hartman, Ingo Molnar, Dietmar Eggemann,
Morten Rasmussen, Chris Redpath, Patrick Bellasi,
Valentin Schneider, Vincent Guittot, Thara Gopinath,
Viresh Kumar, Todd Kjos, Joel Fernandes, Steve Muckle, adharmap,
Saravana Kannan, Pavan Kondeti, Juri Lelli, Eduardo Valentin,
Srinivas Pandruvada, currojerez, Javi Merino
On Thursday 22 Nov 2018 at 16:51:41 (+0100), Rafael J. Wysocki wrote:
> On Thu, Nov 22, 2018 at 4:25 PM Quentin Perret <quentin.perret@arm.com> wrote:
> >
> > On Thursday 22 Nov 2018 at 11:25:45 (+0100), Peter Zijlstra wrote:
> > > On Thu, Nov 22, 2018 at 09:32:39AM +0000, Quentin Perret wrote:
> > > > Hmm, I went too fast, that's totally broken. But there's still something
> > > > we can do with static_branch_{inc,dec} I think. I'll come back later
> > > > with a better solution.
> > >
> > > Right; if you count the rd's that have pd set, it should work-ish. Yes,
> > > much cleaner if you can get it to work.
> >
> > So, I came up with the following code which seems to work OK. It's not
> > as I clean as I'd like, though. The fact that free_pd() can be called in
> > softirq context is annoying to manipulate the static key ...
> >
> > An alternative to this work item workaround is to do static_branch_dec()
> > from build_perf_domains() and next to the three call sites of
> > free_rootdomain() in order to avoid the call_rcu() context. Not very
> > pretty either.
> >
> > Or we can just stick with your original suggestion to carry a boolean
> > around.
>
> What's problematic with carrying a boolean around?
Nothing, I was just trying to see if I could find a more elegant way to
increment/decrement the static key as we create/destroy the perf
domains.
I would not describe the work item thing I came up with as particularly
elegant, though :-)
So, all in all, the boolean is fine by me if we all agree it is nicer.
Thanks,
Quentin
^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH v9 10/15] sched: Introduce a sysctl for Energy Aware Scheduling
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (8 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 09/15] sched: Introduce sched_energy_present static key Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 11/15] sched/fair: Clean-up update_sg_lb_stats parameters Quentin Perret
` (4 subsequent siblings)
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
In its current state, Energy Aware Scheduling (EAS) starts automatically
on asymmetric platforms having an Energy Model (EM). However, there are
users who want to have an EM (for thermal management for example), but
don't want EAS with it.
In order to let users disable EAS explicitly, introduce a new sysctl
called 'sched_energy_aware'. It is enabled by default so that EAS can
start automatically on platforms where it makes sense. Flipping it to 0
rebuilds the scheduling domains and disables EAS.
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
Documentation/sysctl/kernel.txt | 12 ++++++++++++
include/linux/sched/sysctl.h | 7 +++++++
kernel/sched/topology.c | 29 +++++++++++++++++++++++++++++
kernel/sysctl.c | 11 +++++++++++
4 files changed, 59 insertions(+)
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 37a679501ddc..36bee799ee9e 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -78,6 +78,7 @@ show up in /proc/sys/kernel:
- reboot-cmd [ SPARC only ]
- rtsig-max
- rtsig-nr
+- sched_energy_aware
- seccomp/ ==> Documentation/userspace-api/seccomp_filter.rst
- sem
- sem_next_id [ sysv ipc ]
@@ -872,6 +873,17 @@ rtsig-nr shows the number of RT signals currently queued.
==============================================================
+sched_energy_aware:
+
+Enables/disables Energy Aware Scheduling (EAS). EAS starts
+automatically on platforms where it can run (that is,
+platforms with asymmetric CPU topologies and having an Energy
+Model available). If your platform happens to meet the
+requirements for EAS but you do not want to use it, change
+this value to 0.
+
+==============================================================
+
sched_schedstats:
Enables/disables scheduler statistics. Enabling this feature
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index a9c32daeb9d8..99ce6d728df7 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -83,4 +83,11 @@ extern int sysctl_schedstats(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
+#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
+extern unsigned int sysctl_sched_energy_aware;
+extern int sched_energy_aware_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos);
+#endif
+
#endif /* _LINUX_SCHED_SYSCTL_H */
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 1457ef80ee94..8f9dfea60344 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -203,9 +203,35 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
DEFINE_STATIC_KEY_FALSE(sched_energy_present);
#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
+unsigned int sysctl_sched_energy_aware = 1;
DEFINE_MUTEX(sched_energy_mutex);
bool sched_energy_update;
+#ifdef CONFIG_PROC_SYSCTL
+int sched_energy_aware_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ int ret, state;
+
+ if (write && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ if (!ret && write) {
+ state = static_branch_unlikely(&sched_energy_present);
+ if (state != sysctl_sched_energy_aware) {
+ mutex_lock(&sched_energy_mutex);
+ sched_energy_update = 1;
+ rebuild_sched_domains();
+ sched_energy_update = 0;
+ mutex_unlock(&sched_energy_mutex);
+ }
+ }
+
+ return ret;
+}
+#endif
+
static void free_pd(struct perf_domain *pd)
{
struct perf_domain *tmp;
@@ -338,6 +364,9 @@ static void build_perf_domains(const struct cpumask *cpu_map)
struct cpufreq_policy *policy;
struct cpufreq_governor *gov;
+ if (!sysctl_sched_energy_aware)
+ goto free;
+
/* EAS is enabled for asymmetric CPU capacity topologies. */
if (!per_cpu(sd_asym_cpucapacity, cpu)) {
if (sched_debug()) {
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index cc02050fd0c4..481309a11174 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -466,6 +466,17 @@ static struct ctl_table kern_table[] = {
.extra1 = &one,
},
#endif
+#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
+ {
+ .procname = "sched_energy_aware",
+ .data = &sysctl_sched_energy_aware,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = sched_energy_aware_handler,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
+#endif
#ifdef CONFIG_PROVE_LOCKING
{
.procname = "prove_locking",
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 11/15] sched/fair: Clean-up update_sg_lb_stats parameters
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (9 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 10/15] sched: Introduce a sysctl for Energy Aware Scheduling Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 12/15] sched: Add over-utilization/tipping point indicator Quentin Perret
` (3 subsequent siblings)
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
In preparation for the introduction of a new root domain flag which can
be set during load balance (the 'overutilized' flag), clean-up the set
of parameters passed to update_sg_lb_stats(). More specifically, the
'local_group' and 'local_idx' parameters can be removed since they can
easily be reconstructed from within the function.
While at it, transform the 'overload' parameter into a flag stored in
the 'sg_status' parameter hence facilitating the definition of new flags
when needed.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
kernel/sched/fair.c | 27 +++++++++++----------------
kernel/sched/sched.h | 3 +++
2 files changed, 14 insertions(+), 16 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6c42f3e075b9..e21f37129395 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7905,16 +7905,16 @@ static bool update_nohz_stats(struct rq *rq, bool force)
* update_sg_lb_stats - Update sched_group's statistics for load balancing.
* @env: The load balancing environment.
* @group: sched_group whose statistics are to be updated.
- * @load_idx: Load index of sched_domain of this_cpu for load calc.
- * @local_group: Does group contain this_cpu.
* @sgs: variable to hold the statistics for this group.
- * @overload: Indicate pullable load (e.g. >1 runnable task).
+ * @sg_status: Holds flag indicating the status of the sched_group
*/
static inline void update_sg_lb_stats(struct lb_env *env,
- struct sched_group *group, int load_idx,
- int local_group, struct sg_lb_stats *sgs,
- bool *overload)
+ struct sched_group *group,
+ struct sg_lb_stats *sgs,
+ int *sg_status)
{
+ int local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(group));
+ int load_idx = get_sd_load_idx(env->sd, env->idle);
unsigned long load;
int i, nr_running;
@@ -7938,7 +7938,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
nr_running = rq->nr_running;
if (nr_running > 1)
- *overload = true;
+ *sg_status |= SG_OVERLOAD;
#ifdef CONFIG_NUMA_BALANCING
sgs->nr_numa_running += rq->nr_numa_running;
@@ -7954,7 +7954,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
sgs->group_misfit_task_load < rq->misfit_task_load) {
sgs->group_misfit_task_load = rq->misfit_task_load;
- *overload = 1;
+ *sg_status |= SG_OVERLOAD;
}
}
@@ -8099,17 +8099,14 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
struct sched_group *sg = env->sd->groups;
struct sg_lb_stats *local = &sds->local_stat;
struct sg_lb_stats tmp_sgs;
- int load_idx;
- bool overload = false;
bool prefer_sibling = child && child->flags & SD_PREFER_SIBLING;
+ int sg_status = 0;
#ifdef CONFIG_NO_HZ_COMMON
if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
env->flags |= LBF_NOHZ_STATS;
#endif
- load_idx = get_sd_load_idx(env->sd, env->idle);
-
do {
struct sg_lb_stats *sgs = &tmp_sgs;
int local_group;
@@ -8124,8 +8121,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
update_group_capacity(env->sd, env->dst_cpu);
}
- update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
- &overload);
+ update_sg_lb_stats(env, sg, sgs, &sg_status);
if (local_group)
goto next_group;
@@ -8175,8 +8171,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
if (!env->sd->parent) {
/* update overload indicator if we are at root domain */
- if (READ_ONCE(env->dst_rq->rd->overload) != overload)
- WRITE_ONCE(env->dst_rq->rd->overload, overload);
+ WRITE_ONCE(env->dst_rq->rd->overload, sg_status & SG_OVERLOAD);
}
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 5b636a8aa900..bd759ade7351 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -715,6 +715,9 @@ struct perf_domain {
struct rcu_head rcu;
};
+/* Scheduling group status flags */
+#define SG_OVERLOAD 0x1 /* More than one runnable task on a CPU. */
+
/*
* We add the notion of a root-domain which will be used to define per-domain
* variables. Each exclusive cpuset essentially defines an island domain by
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 12/15] sched: Add over-utilization/tipping point indicator
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (10 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 11/15] sched/fair: Clean-up update_sg_lb_stats parameters Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 13/15] sched/fair: Introduce an energy estimation helper function Quentin Perret
` (2 subsequent siblings)
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
From: Morten Rasmussen <morten.rasmussen@arm.com>
Energy-aware scheduling is only meant to be active while the system is
_not_ over-utilized. That is, there are spare cycles available to shift
tasks around based on their actual utilization to get a more
energy-efficient task distribution without depriving any tasks. When
above the tipping point task placement is done the traditional way based
on load_avg, spreading the tasks across as many cpus as possible based
on priority scaled load to preserve smp_nice. Below the tipping point we
want to use util_avg instead. We need to define a criteria for when we
make the switch.
The util_avg for each cpu converges towards 100% regardless of how many
additional tasks we may put on it. If we define over-utilized as:
sum_{cpus}(rq.cfs.avg.util_avg) + margin > sum_{cpus}(rq.capacity)
some individual cpus may be over-utilized running multiple tasks even
when the above condition is false. That should be okay as long as we try
to spread the tasks out to avoid per-cpu over-utilization as much as
possible and if all tasks have the _same_ priority. If the latter isn't
true, we have to consider priority to preserve smp_nice.
For example, we could have n_cpus nice=-10 util_avg=55% tasks and
n_cpus/2 nice=0 util_avg=60% tasks. Balancing based on util_avg we are
likely to end up with nice=-10 tasks sharing cpus and nice=0 tasks
getting their own as we 1.5*n_cpus tasks in total and 55%+55% is less
over-utilized than 55%+60% for those cpus that have to be shared. The
system utilization is only 85% of the system capacity, but we are
breaking smp_nice.
To be sure not to break smp_nice, we have defined over-utilization
conservatively as when any cpu in the system is fully utilized at its
highest frequency instead:
cpu_rq(any).cfs.avg.util_avg + margin > cpu_rq(any).capacity
IOW, as soon as one cpu is (nearly) 100% utilized, we switch to load_avg
to factor in priority to preserve smp_nice.
With this definition, we can skip periodic load-balance as no cpu has an
always-running task when the system is not over-utilized. All tasks will
be periodic and we can balance them at wake-up. This conservative
condition does however mean that some scenarios that could benefit from
energy-aware decisions even if one cpu is fully utilized would not get
those benefits.
For systems where some cpus might have reduced capacity on some cpus
(RT-pressure and/or big.LITTLE), we want periodic load-balance checks as
soon a just a single cpu is fully utilized as it might one of those with
reduced capacity and in that case we want to migrate it.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
[ Added a comment explaining why new tasks are not accounted during
overutilization detection ]
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
kernel/sched/fair.c | 59 ++++++++++++++++++++++++++++++++++++++++++--
kernel/sched/sched.h | 4 +++
2 files changed, 61 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e21f37129395..c3b2dad72c9c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5082,6 +5082,24 @@ static inline void hrtick_update(struct rq *rq)
}
#endif
+#ifdef CONFIG_SMP
+static inline unsigned long cpu_util(int cpu);
+static unsigned long capacity_of(int cpu);
+
+static inline bool cpu_overutilized(int cpu)
+{
+ return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
+}
+
+static inline void update_overutilized_status(struct rq *rq)
+{
+ if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu))
+ WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
+}
+#else
+static inline void update_overutilized_status(struct rq *rq) { }
+#endif
+
/*
* The enqueue_task method is called before nr_running is
* increased. Here we update the fair scheduling stats and
@@ -5139,8 +5157,26 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
update_cfs_group(se);
}
- if (!se)
+ if (!se) {
add_nr_running(rq, 1);
+ /*
+ * Since new tasks are assigned an initial util_avg equal to
+ * half of the spare capacity of their CPU, tiny tasks have the
+ * ability to cross the overutilized threshold, which will
+ * result in the load balancer ruining all the task placement
+ * done by EAS. As a way to mitigate that effect, do not account
+ * for the first enqueue operation of new tasks during the
+ * overutilized flag detection.
+ *
+ * A better way of solving this problem would be to wait for
+ * the PELT signals of tasks to converge before taking them
+ * into account, but that is not straightforward to implement,
+ * and the following generally works well enough in practice.
+ */
+ if (flags & ENQUEUE_WAKEUP)
+ update_overutilized_status(rq);
+
+ }
hrtick_update(rq);
}
@@ -7940,6 +7976,9 @@ static inline void update_sg_lb_stats(struct lb_env *env,
if (nr_running > 1)
*sg_status |= SG_OVERLOAD;
+ if (cpu_overutilized(i))
+ *sg_status |= SG_OVERUTILIZED;
+
#ifdef CONFIG_NUMA_BALANCING
sgs->nr_numa_running += rq->nr_numa_running;
sgs->nr_preferred_running += rq->nr_preferred_running;
@@ -8170,8 +8209,15 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
env->fbq_type = fbq_classify_group(&sds->busiest_stat);
if (!env->sd->parent) {
+ struct root_domain *rd = env->dst_rq->rd;
+
/* update overload indicator if we are at root domain */
- WRITE_ONCE(env->dst_rq->rd->overload, sg_status & SG_OVERLOAD);
+ WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD);
+
+ /* Update over-utilization (tipping point, U >= 0) indicator */
+ WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
+ } else if (sg_status & SG_OVERUTILIZED) {
+ WRITE_ONCE(env->dst_rq->rd->overutilized, SG_OVERUTILIZED);
}
}
@@ -8398,6 +8444,14 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
* this level.
*/
update_sd_lb_stats(env, &sds);
+
+ if (static_branch_unlikely(&sched_energy_present)) {
+ struct root_domain *rd = env->dst_rq->rd;
+
+ if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
+ goto out_balanced;
+ }
+
local = &sds.local_stat;
busiest = &sds.busiest_stat;
@@ -9798,6 +9852,7 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
task_tick_numa(rq, curr);
update_misfit_status(curr, rq);
+ update_overutilized_status(task_rq(curr));
}
/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index bd759ade7351..30f59a912289 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -717,6 +717,7 @@ struct perf_domain {
/* Scheduling group status flags */
#define SG_OVERLOAD 0x1 /* More than one runnable task on a CPU. */
+#define SG_OVERUTILIZED 0x2 /* One or more CPUs are over-utilized. */
/*
* We add the notion of a root-domain which will be used to define per-domain
@@ -740,6 +741,9 @@ struct root_domain {
*/
int overload;
+ /* Indicate one or more cpus over-utilized (tipping point) */
+ int overutilized;
+
/*
* The bit corresponding to a CPU gets set here if such CPU has more
* than one runnable -deadline task (as it is below for RT tasks).
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 13/15] sched/fair: Introduce an energy estimation helper function
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (11 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 12/15] sched: Add over-utilization/tipping point indicator Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-21 14:28 ` Peter Zijlstra
2018-11-19 14:18 ` [PATCH v9 14/15] sched/fair: Select an energy-efficient CPU on task wake-up Quentin Perret
2018-11-19 14:18 ` [PATCH v9 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model Quentin Perret
14 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
In preparation for the definition of an energy-aware wakeup path,
introduce a helper function to estimate the consequence on system energy
when a specific task wakes-up on a specific CPU. compute_energy()
estimates the capacity state to be reached by all performance domains
and estimates the consumption of each online CPU according to its Energy
Model and its percentage of busy time.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
kernel/sched/fair.c | 76 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 76 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c3b2dad72c9c..a20018ad9236 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6377,6 +6377,82 @@ static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
return !task_fits_capacity(p, min_cap);
}
+/*
+ * Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued)
+ * to @dst_cpu.
+ */
+static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
+{
+ struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
+ unsigned long util_est, util = READ_ONCE(cfs_rq->avg.util_avg);
+
+ /*
+ * If @p migrates from @cpu to another, remove its contribution. Or,
+ * if @p migrates from another CPU to @cpu, add its contribution. In
+ * the other cases, @cpu is not impacted by the migration, so the
+ * util_avg should already be correct.
+ */
+ if (task_cpu(p) == cpu && dst_cpu != cpu)
+ sub_positive(&util, task_util(p));
+ else if (task_cpu(p) != cpu && dst_cpu == cpu)
+ util += task_util(p);
+
+ if (sched_feat(UTIL_EST)) {
+ util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);
+
+ /*
+ * During wake-up, the task isn't enqueued yet and doesn't
+ * appear in the cfs_rq->avg.util_est.enqueued of any rq,
+ * so just add it (if needed) to "simulate" what will be
+ * cpu_util() after the task has been enqueued.
+ */
+ if (dst_cpu == cpu)
+ util_est += _task_util_est(p);
+
+ util = max(util, util_est);
+ }
+
+ return min(util, capacity_orig_of(cpu));
+}
+
+/*
+ * compute_energy(): Estimates the energy that would be consumed if @p was
+ * migrated to @dst_cpu. compute_energy() predicts what will be the utilization
+ * landscape of the * CPUs after the task migration, and uses the Energy Model
+ * to compute what would be the energy if we decided to actually migrate that
+ * task.
+ */
+static long
+compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
+{
+ long util, max_util, sum_util, energy = 0;
+ int cpu;
+
+ for (; pd; pd = pd->next) {
+ max_util = sum_util = 0;
+ /*
+ * The capacity state of CPUs of the current rd can be driven by
+ * CPUs of another rd if they belong to the same performance
+ * domain. So, account for the utilization of these CPUs too
+ * by masking pd with cpu_online_mask instead of the rd span.
+ *
+ * If an entire performance domain is outside of the current rd,
+ * it will not appear in its pd list and will not be accounted
+ * by compute_energy().
+ */
+ for_each_cpu_and(cpu, perf_domain_span(pd), cpu_online_mask) {
+ util = cpu_util_next(cpu, p, dst_cpu);
+ util = schedutil_energy_util(cpu, util);
+ max_util = max(util, max_util);
+ sum_util += util;
+ }
+
+ energy += em_pd_energy(pd->em_pd, max_util, sum_util);
+ }
+
+ return energy;
+}
+
/*
* select_task_rq_fair: Select target runqueue for the waking task in domains
* that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* Re: [PATCH v9 13/15] sched/fair: Introduce an energy estimation helper function
2018-11-19 14:18 ` [PATCH v9 13/15] sched/fair: Introduce an energy estimation helper function Quentin Perret
@ 2018-11-21 14:28 ` Peter Zijlstra
2018-11-21 16:05 ` Quentin Perret
0 siblings, 1 reply; 35+ messages in thread
From: Peter Zijlstra @ 2018-11-21 14:28 UTC (permalink / raw)
To: Quentin Perret
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Mon, Nov 19, 2018 at 02:18:55PM +0000, Quentin Perret wrote:
> +static long
> +compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
> +{
> + long util, max_util, sum_util, energy = 0;
> + int cpu;
> +
> + for (; pd; pd = pd->next) {
> + max_util = sum_util = 0;
> + /*
> + * The capacity state of CPUs of the current rd can be driven by
> + * CPUs of another rd if they belong to the same performance
> + * domain. So, account for the utilization of these CPUs too
> + * by masking pd with cpu_online_mask instead of the rd span.
> + *
> + * If an entire performance domain is outside of the current rd,
> + * it will not appear in its pd list and will not be accounted
> + * by compute_energy().
> + */
> + for_each_cpu_and(cpu, perf_domain_span(pd), cpu_online_mask) {
Should that not be cpu_active_mask ?
> + util = cpu_util_next(cpu, p, dst_cpu);
> + util = schedutil_energy_util(cpu, util);
> + max_util = max(util, max_util);
> + sum_util += util;
> + }
> +
> + energy += em_pd_energy(pd->em_pd, max_util, sum_util);
> + }
> +
> + return energy;
> +}
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 13/15] sched/fair: Introduce an energy estimation helper function
2018-11-21 14:28 ` Peter Zijlstra
@ 2018-11-21 16:05 ` Quentin Perret
2018-11-22 13:56 ` Peter Zijlstra
0 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-21 16:05 UTC (permalink / raw)
To: Peter Zijlstra
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Wednesday 21 Nov 2018 at 15:28:03 (+0100), Peter Zijlstra wrote:
> On Mon, Nov 19, 2018 at 02:18:55PM +0000, Quentin Perret wrote:
> > +static long
> > +compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
> > +{
> > + long util, max_util, sum_util, energy = 0;
> > + int cpu;
> > +
> > + for (; pd; pd = pd->next) {
> > + max_util = sum_util = 0;
> > + /*
> > + * The capacity state of CPUs of the current rd can be driven by
> > + * CPUs of another rd if they belong to the same performance
> > + * domain. So, account for the utilization of these CPUs too
> > + * by masking pd with cpu_online_mask instead of the rd span.
> > + *
> > + * If an entire performance domain is outside of the current rd,
> > + * it will not appear in its pd list and will not be accounted
> > + * by compute_energy().
> > + */
> > + for_each_cpu_and(cpu, perf_domain_span(pd), cpu_online_mask) {
>
> Should that not be cpu_active_mask ?
Hmm, I must admit I'm sometimes a bit confused by the exact difference
between these masks, so maybe yeah ...
IIUC, cpu_active_mask is basically the set of CPUs on which the
scheduler is actually allowed to migrate tasks. Is that correct ?
I have always seen cpu_online_mask as a superset of cpu_active_mask
which can also include CPUs which are still running 'special' tasks
(kthreads and things like that I assume) although not allowed for
migration any more (or not yet) because we're in the process of
hotplugging that CPU.
So, the thing is, I'm not trying to select a CPU candidate for my task
here, I'm trying to understand what's the energy impact of a migration.
That involves all CPUs that are running _something_ in a perf domain
no matter if they're allowed to run more tasks or not. I mean, raising
the OPP will make running online && !active CPUs more expensive as well.
That's why I thought cpu_online_mask was good match here.
Or maybe I'm confused again :-)
>
> > + util = cpu_util_next(cpu, p, dst_cpu);
> > + util = schedutil_energy_util(cpu, util);
> > + max_util = max(util, max_util);
> > + sum_util += util;
> > + }
> > +
> > + energy += em_pd_energy(pd->em_pd, max_util, sum_util);
> > + }
> > +
> > + return energy;
> > +}
Thanks,
Quentin
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 13/15] sched/fair: Introduce an energy estimation helper function
2018-11-21 16:05 ` Quentin Perret
@ 2018-11-22 13:56 ` Peter Zijlstra
0 siblings, 0 replies; 35+ messages in thread
From: Peter Zijlstra @ 2018-11-22 13:56 UTC (permalink / raw)
To: Quentin Perret
Cc: rjw, linux-kernel, linux-pm, gregkh, mingo, dietmar.eggemann,
morten.rasmussen, chris.redpath, patrick.bellasi,
valentin.schneider, vincent.guittot, thara.gopinath,
viresh.kumar, tkjos, joel, smuckle, adharmap, skannan, pkondeti,
juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On Wed, Nov 21, 2018 at 04:05:27PM +0000, Quentin Perret wrote:
> On Wednesday 21 Nov 2018 at 15:28:03 (+0100), Peter Zijlstra wrote:
> > On Mon, Nov 19, 2018 at 02:18:55PM +0000, Quentin Perret wrote:
> > > +static long
> > > +compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
> > > +{
> > > + long util, max_util, sum_util, energy = 0;
> > > + int cpu;
> > > +
> > > + for (; pd; pd = pd->next) {
> > > + max_util = sum_util = 0;
> > > + /*
> > > + * The capacity state of CPUs of the current rd can be driven by
> > > + * CPUs of another rd if they belong to the same performance
> > > + * domain. So, account for the utilization of these CPUs too
> > > + * by masking pd with cpu_online_mask instead of the rd span.
> > > + *
> > > + * If an entire performance domain is outside of the current rd,
> > > + * it will not appear in its pd list and will not be accounted
> > > + * by compute_energy().
> > > + */
> > > + for_each_cpu_and(cpu, perf_domain_span(pd), cpu_online_mask) {
> >
> > Should that not be cpu_active_mask ?
>
> Hmm, I must admit I'm sometimes a bit confused by the exact difference
> between these masks, so maybe yeah ...
>
> IIUC, cpu_active_mask is basically the set of CPUs on which the
> scheduler is actually allowed to migrate tasks. Is that correct ?
Yep. Which is a strict subset of online. The difference only matters
during hotplug. We take a CPU out of active before we take if offline
and we add it to active only after the CPU is fully online and
scheduling.
> I have always seen cpu_online_mask as a superset of cpu_active_mask
> which can also include CPUs which are still running 'special' tasks
> (kthreads and things like that I assume) although not allowed for
> migration any more (or not yet) because we're in the process of
> hotplugging that CPU.
Right.
> So, the thing is, I'm not trying to select a CPU candidate for my task
> here, I'm trying to understand what's the energy impact of a migration.
> That involves all CPUs that are running _something_ in a perf domain
> no matter if they're allowed to run more tasks or not. I mean, raising
> the OPP will make running online && !active CPUs more expensive as well.
> That's why I thought cpu_online_mask was good match here.
Ah, fair enough. Thanks!
^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH v9 14/15] sched/fair: Select an energy-efficient CPU on task wake-up
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (12 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 13/15] sched/fair: Introduce an energy estimation helper function Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-19 14:18 ` [PATCH v9 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model Quentin Perret
14 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
If an Energy Model (EM) is available and if the system isn't
overutilized, re-route waking tasks into an energy-aware placement
algorithm. The selection of an energy-efficient CPU for a task
is achieved by estimating the impact on system-level active energy
resulting from the placement of the task on the CPU with the highest
spare capacity in each performance domain. This strategy spreads tasks
in a performance domain and avoids overly aggressive task packing. The
best CPU energy-wise is then selected if it saves a large enough amount
of energy with respect to prev_cpu.
Although it has already shown significant benefits on some existing
targets, this approach cannot scale to platforms with numerous CPUs.
This is an attempt to do something useful as writing a fast heuristic
that performs reasonably well on a broad spectrum of architectures isn't
an easy task. As such, the scope of usability of the energy-aware
wake-up path is restricted to systems with the SD_ASYM_CPUCAPACITY flag
set, and where the EM isn't too complex.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
kernel/sched/fair.c | 143 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 141 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a20018ad9236..d73e7db5976a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6453,6 +6453,137 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
return energy;
}
+/*
+ * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
+ * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
+ * spare capacity in each performance domain and uses it as a potential
+ * candidate to execute the task. Then, it uses the Energy Model to figure
+ * out which of the CPU candidates is the most energy-efficient.
+ *
+ * The rationale for this heuristic is as follows. In a performance domain,
+ * all the most energy efficient CPU candidates (according to the Energy
+ * Model) are those for which we'll request a low frequency. When there are
+ * several CPUs for which the frequency request will be the same, we don't
+ * have enough data to break the tie between them, because the Energy Model
+ * only includes active power costs. With this model, if we assume that
+ * frequency requests follow utilization (e.g. using schedutil), the CPU with
+ * the maximum spare capacity in a performance domain is guaranteed to be among
+ * the best candidates of the performance domain.
+ *
+ * In practice, it could be preferable from an energy standpoint to pack
+ * small tasks on a CPU in order to let other CPUs go in deeper idle states,
+ * but that could also hurt our chances to go cluster idle, and we have no
+ * ways to tell with the current Energy Model if this is actually a good
+ * idea or not. So, find_energy_efficient_cpu() basically favors
+ * cluster-packing, and spreading inside a cluster. That should at least be
+ * a good thing for latency, and this is consistent with the idea that most
+ * of the energy savings of EAS come from the asymmetry of the system, and
+ * not so much from breaking the tie between identical CPUs. That's also the
+ * reason why EAS is enabled in the topology code only for systems where
+ * SD_ASYM_CPUCAPACITY is set.
+ *
+ * NOTE: Forkees are not accepted in the energy-aware wake-up path because
+ * they don't have any useful utilization data yet and it's not possible to
+ * forecast their impact on energy consumption. Consequently, they will be
+ * placed by find_idlest_cpu() on the least loaded CPU, which might turn out
+ * to be energy-inefficient in some use-cases. The alternative would be to
+ * bias new tasks towards specific types of CPUs first, or to try to infer
+ * their util_avg from the parent task, but those heuristics could hurt
+ * other use-cases too. So, until someone finds a better way to solve this,
+ * let's keep things simple by re-using the existing slow path.
+ */
+
+static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
+{
+ unsigned long prev_energy = ULONG_MAX, best_energy = ULONG_MAX;
+ struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
+ int cpu, best_energy_cpu = prev_cpu;
+ struct perf_domain *head, *pd;
+ unsigned long cpu_cap, util;
+ struct sched_domain *sd;
+
+ rcu_read_lock();
+ pd = rcu_dereference(rd->pd);
+ if (!pd || READ_ONCE(rd->overutilized))
+ goto fail;
+ head = pd;
+
+ /*
+ * Energy-aware wake-up happens on the lowest sched_domain starting
+ * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
+ */
+ sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
+ while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
+ sd = sd->parent;
+ if (!sd)
+ goto fail;
+
+ sync_entity_load_avg(&p->se);
+ if (!task_util_est(p))
+ goto unlock;
+
+ for (; pd; pd = pd->next) {
+ unsigned long cur_energy, spare_cap, max_spare_cap = 0;
+ int max_spare_cap_cpu = -1;
+
+ for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) {
+ if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
+ continue;
+
+ /* Skip CPUs that will be overutilized. */
+ util = cpu_util_next(cpu, p, cpu);
+ cpu_cap = capacity_of(cpu);
+ if (cpu_cap * 1024 < util * capacity_margin)
+ continue;
+
+ /* Always use prev_cpu as a candidate. */
+ if (cpu == prev_cpu) {
+ prev_energy = compute_energy(p, prev_cpu, head);
+ best_energy = min(best_energy, prev_energy);
+ continue;
+ }
+
+ /*
+ * Find the CPU with the maximum spare capacity in
+ * the performance domain
+ */
+ spare_cap = cpu_cap - util;
+ if (spare_cap > max_spare_cap) {
+ max_spare_cap = spare_cap;
+ max_spare_cap_cpu = cpu;
+ }
+ }
+
+ /* Evaluate the energy impact of using this CPU. */
+ if (max_spare_cap_cpu >= 0) {
+ cur_energy = compute_energy(p, max_spare_cap_cpu, head);
+ if (cur_energy < best_energy) {
+ best_energy = cur_energy;
+ best_energy_cpu = max_spare_cap_cpu;
+ }
+ }
+ }
+unlock:
+ rcu_read_unlock();
+
+ /*
+ * Pick the best CPU if prev_cpu cannot be used, or if it saves at
+ * least 6% of the energy used by prev_cpu.
+ */
+ if (prev_energy == ULONG_MAX)
+ return best_energy_cpu;
+
+ if ((prev_energy - best_energy) > (prev_energy >> 4))
+ return best_energy_cpu;
+
+ return prev_cpu;
+
+fail:
+ rcu_read_unlock();
+
+ return -1;
+}
+
/*
* select_task_rq_fair: Select target runqueue for the waking task in domains
* that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
@@ -6476,8 +6607,16 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
if (sd_flag & SD_BALANCE_WAKE) {
record_wakee(p);
- want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
- && cpumask_test_cpu(cpu, &p->cpus_allowed);
+
+ if (static_branch_unlikely(&sched_energy_present)) {
+ new_cpu = find_energy_efficient_cpu(p, prev_cpu);
+ if (new_cpu >= 0)
+ return new_cpu;
+ new_cpu = prev_cpu;
+ }
+
+ want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu) &&
+ cpumask_test_cpu(cpu, &p->cpus_allowed);
}
rcu_read_lock();
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* [PATCH v9 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model
2018-11-19 14:18 [PATCH v9 00/15] Energy Aware Scheduling Quentin Perret
` (13 preceding siblings ...)
2018-11-19 14:18 ` [PATCH v9 14/15] sched/fair: Select an energy-efficient CPU on task wake-up Quentin Perret
@ 2018-11-19 14:18 ` Quentin Perret
2018-11-20 6:19 ` Viresh Kumar
14 siblings, 1 reply; 35+ messages in thread
From: Quentin Perret @ 2018-11-19 14:18 UTC (permalink / raw)
To: peterz, rjw, linux-kernel, linux-pm
Cc: gregkh, mingo, dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, viresh.kumar, tkjos, joel, smuckle, adharmap,
skannan, pkondeti, juri.lelli, edubezval, srinivas.pandruvada,
currojerez, javi.merino, quentin.perret
*******************************************************************
* This patch illustrates the usage of the newly introduced Energy *
* Model framework and isn't supposed to be merged as-is. *
*******************************************************************
The Energy Model framework provides an API to register the active power
of CPUs. Call this API from the cpufreq-dt driver with an estimation
of the power as P = C * V^2 * f with C, V, and f respectively the
capacitance of the CPU and the voltage and frequency of the OPP.
The CPU capacitance is read from the "dynamic-power-coefficient" DT
binding (originally introduced for thermal/IPA), and the voltage and
frequency values from PM_OPP.
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
drivers/cpufreq/cpufreq-dt.c | 48 +++++++++++++++++++++++++++++++++++-
1 file changed, 47 insertions(+), 1 deletion(-)
diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
index e58bfcb1169e..4cfef5554d86 100644
--- a/drivers/cpufreq/cpufreq-dt.c
+++ b/drivers/cpufreq/cpufreq-dt.c
@@ -16,6 +16,7 @@
#include <linux/cpu_cooling.h>
#include <linux/cpufreq.h>
#include <linux/cpumask.h>
+#include <linux/energy_model.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/of.h>
@@ -150,8 +151,50 @@ static int resources_available(void)
return 0;
}
+static int __maybe_unused of_est_power(unsigned long *mW, unsigned long *KHz,
+ int cpu)
+{
+ unsigned long mV, Hz, MHz;
+ struct device *cpu_dev;
+ struct dev_pm_opp *opp;
+ struct device_node *np;
+ u32 cap;
+ u64 tmp;
+
+ cpu_dev = get_cpu_device(cpu);
+ if (!cpu_dev)
+ return -ENODEV;
+
+ np = of_node_get(cpu_dev->of_node);
+ if (!np)
+ return -EINVAL;
+
+ if (of_property_read_u32(np, "dynamic-power-coefficient", &cap))
+ return -EINVAL;
+
+ Hz = *KHz * 1000;
+ opp = dev_pm_opp_find_freq_ceil(cpu_dev, &Hz);
+ if (IS_ERR(opp))
+ return -EINVAL;
+
+ mV = dev_pm_opp_get_voltage(opp) / 1000;
+ dev_pm_opp_put(opp);
+ if (!mV)
+ return -EINVAL;
+
+ MHz = Hz / 1000000;
+ tmp = (u64)cap * mV * mV * MHz;
+ do_div(tmp, 1000000000);
+
+ *mW = (unsigned long)tmp;
+ *KHz = Hz / 1000;
+
+ return 0;
+}
+
static int cpufreq_init(struct cpufreq_policy *policy)
{
+ struct em_data_callback em_cb = EM_DATA_CB(of_est_power);
struct cpufreq_frequency_table *freq_table;
struct opp_table *opp_table = NULL;
struct private_data *priv;
@@ -160,7 +203,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
unsigned int transition_latency;
bool fallback = false;
const char *name;
- int ret;
+ int ret, nr_opp;
cpu_dev = get_cpu_device(policy->cpu);
if (!cpu_dev) {
@@ -237,6 +280,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
ret = -EPROBE_DEFER;
goto out_free_opp;
}
+ nr_opp = ret;
if (fallback) {
cpumask_setall(policy->cpus);
@@ -280,6 +324,8 @@ static int cpufreq_init(struct cpufreq_policy *policy)
policy->cpuinfo.transition_latency = transition_latency;
policy->dvfs_possible_from_any_cpu = true;
+ em_register_perf_domain(policy->cpus, nr_opp, &em_cb);
+
return 0;
out_free_cpufreq_table:
--
2.19.1
^ permalink raw reply related [flat|nested] 35+ messages in thread* Re: [PATCH v9 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model
2018-11-19 14:18 ` [PATCH v9 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model Quentin Perret
@ 2018-11-20 6:19 ` Viresh Kumar
2018-11-20 10:01 ` Quentin Perret
0 siblings, 1 reply; 35+ messages in thread
From: Viresh Kumar @ 2018-11-20 6:19 UTC (permalink / raw)
To: Quentin Perret
Cc: peterz, rjw, linux-kernel, linux-pm, gregkh, mingo,
dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, tkjos, joel, smuckle, adharmap, skannan,
pkondeti, juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
On 19-11-18, 14:18, Quentin Perret wrote:
> static int cpufreq_init(struct cpufreq_policy *policy)
> {
> + struct em_data_callback em_cb = EM_DATA_CB(of_est_power);
> struct cpufreq_frequency_table *freq_table;
> struct opp_table *opp_table = NULL;
> struct private_data *priv;
> @@ -160,7 +203,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> unsigned int transition_latency;
> bool fallback = false;
> const char *name;
> - int ret;
> + int ret, nr_opp;
>
> cpu_dev = get_cpu_device(policy->cpu);
> if (!cpu_dev) {
> @@ -237,6 +280,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> ret = -EPROBE_DEFER;
> goto out_free_opp;
> }
> + nr_opp = ret;
>
> if (fallback) {
> cpumask_setall(policy->cpus);
> @@ -280,6 +324,8 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> policy->cpuinfo.transition_latency = transition_latency;
> policy->dvfs_possible_from_any_cpu = true;
>
> + em_register_perf_domain(policy->cpus, nr_opp, &em_cb);
> +
> return 0;
>
> out_free_cpufreq_table:
I haven't gone deep into the series, but why don't we need something
like em_unregister_perf_domain()? That can be used if the cpufreq
driver goes away. Else loading/unloading/loading the cpufreq driver
may register the perf-domain callback again.
--
viresh
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH v9 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model
2018-11-20 6:19 ` Viresh Kumar
@ 2018-11-20 10:01 ` Quentin Perret
0 siblings, 0 replies; 35+ messages in thread
From: Quentin Perret @ 2018-11-20 10:01 UTC (permalink / raw)
To: Viresh Kumar
Cc: peterz, rjw, linux-kernel, linux-pm, gregkh, mingo,
dietmar.eggemann, morten.rasmussen, chris.redpath,
patrick.bellasi, valentin.schneider, vincent.guittot,
thara.gopinath, tkjos, joel, smuckle, adharmap, skannan,
pkondeti, juri.lelli, edubezval, srinivas.pandruvada, currojerez,
javi.merino
Hi Viresh,
On Tuesday 20 Nov 2018 at 11:49:25 (+0530), Viresh Kumar wrote:
> On 19-11-18, 14:18, Quentin Perret wrote:
> > static int cpufreq_init(struct cpufreq_policy *policy)
> > {
> > + struct em_data_callback em_cb = EM_DATA_CB(of_est_power);
> > struct cpufreq_frequency_table *freq_table;
> > struct opp_table *opp_table = NULL;
> > struct private_data *priv;
> > @@ -160,7 +203,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> > unsigned int transition_latency;
> > bool fallback = false;
> > const char *name;
> > - int ret;
> > + int ret, nr_opp;
> >
> > cpu_dev = get_cpu_device(policy->cpu);
> > if (!cpu_dev) {
> > @@ -237,6 +280,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> > ret = -EPROBE_DEFER;
> > goto out_free_opp;
> > }
> > + nr_opp = ret;
> >
> > if (fallback) {
> > cpumask_setall(policy->cpus);
> > @@ -280,6 +324,8 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> > policy->cpuinfo.transition_latency = transition_latency;
> > policy->dvfs_possible_from_any_cpu = true;
> >
> > + em_register_perf_domain(policy->cpus, nr_opp, &em_cb);
> > +
> > return 0;
> >
> > out_free_cpufreq_table:
>
> I haven't gone deep into the series, but why don't we need something
> like em_unregister_perf_domain()? That can be used if the cpufreq
> driver goes away. Else loading/unloading/loading the cpufreq driver
> may register the perf-domain callback again.
Right, that's a good point. Registering the perf-domain multiple times
is harmless -- all but the first registration will be ignored. That
_should_ be documented somewhere in patch 03. I'll double check and add
the doc if that's not the case.
The overall idea so far has been to keep the EM framework as simple as
possible. We allocate the EM once and it stays in memory forever. That
makes it really easy for the scheduler (for instance) to manipulate
pointers to perf domains without having to worry about them being
unregistered. We could definitely do something smarter to
register/unregister the PDs dynamically using refcount or something,
but hopefully this is something we can do later, if need be.
Thanks,
Quentin
^ permalink raw reply [flat|nested] 35+ messages in thread