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Message-Id: <20161027174108.31139-3-patrick.bellasi@arm.com>
Date: Thu, 27 Oct 2016 18:41:02 +0100
From: Patrick Bellasi <patrick.bellasi@....com>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Steve Muckle <steve.muckle@...aro.org>,
Leo Yan <leo.yan@...aro.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
"Rafael J . Wysocki" <rjw@...ysocki.net>,
Todd Kjos <tkjos@...gle.com>,
Srinath Sridharan <srinathsr@...gle.com>,
Andres Oportus <andresoportus@...gle.com>,
Juri Lelli <juri.lelli@....com>,
Morten Rasmussen <morten.rasmussen@....com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Chris Redpath <chris.redpath@....com>,
Robin Randhawa <robin.randhawa@....com>,
Patrick Bellasi <patrick.bellasi@....com>,
Ingo Molnar <mingo@...hat.com>
Subject: [RFC v2 2/8] sched/tune: add sysctl interface to define a boost value
The current (CFS) scheduler implementation does not allow "to boost"
tasks performance by running them at a higher OPP compared to the
minimum required to meet their workload demands.
To support tasks performance boosting the scheduler should provide a
"knob" which allows to tune how much the system is going to be optimised
for energy efficiency vs performance boosting.
It's worth to notice that by energy-efficiency we mean running a CPU at
the minimum OPP which satisfy its utilization while for performance
boosting we mean running a task as fast as possible.
This patch is the first of a series which provides a simple interface to
define a tuning knob. One system-wide "boost" tunable is exposed via:
/proc/sys/kernel/sched_cfs_boost
which can be configured in the range [0..100], to define a percentage
where:
0% boost requires to operate in "standard" mode by scheduling
tasks at the minimum capacities required by the workload demand
100% boost requires to push at maximum the task performances,
"regardless" of the incurred energy consumption
A boost value in between these two boundaries is used to bias the
power/performance trade-off, the higher the boost value the more the
scheduler is biased toward performance boosting instead of energy
efficiency.
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Patrick Bellasi <patrick.bellasi@....com>
---
include/linux/sched/sysctl.h | 16 ++++++++++++++++
init/Kconfig | 31 +++++++++++++++++++++++++++++++
kernel/sched/Makefile | 1 +
kernel/sched/tune.c | 23 +++++++++++++++++++++++
kernel/sysctl.c | 11 +++++++++++
5 files changed, 82 insertions(+)
create mode 100644 kernel/sched/tune.c
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 4411453..5bfbb14 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -55,6 +55,22 @@ extern int sysctl_sched_rt_runtime;
extern unsigned int sysctl_sched_cfs_bandwidth_slice;
#endif
+#ifdef CONFIG_SCHED_TUNE
+extern unsigned int sysctl_sched_cfs_boost;
+int sysctl_sched_cfs_boost_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length,
+ loff_t *ppos);
+static inline unsigned int get_sysctl_sched_cfs_boost(void)
+{
+ return sysctl_sched_cfs_boost;
+}
+#else
+static inline unsigned int get_sysctl_sched_cfs_boost(void)
+{
+ return 0;
+}
+#endif
+
#ifdef CONFIG_SCHED_AUTOGROUP
extern unsigned int sysctl_sched_autogroup_enabled;
#endif
diff --git a/init/Kconfig b/init/Kconfig
index 34407f1..461e052 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1248,6 +1248,37 @@ config SCHED_AUTOGROUP
desktop applications. Task group autogeneration is currently based
upon task session.
+config SCHED_TUNE
+ bool "Boosting for CFS tasks (EXPERIMENTAL)"
+ depends on SMP
+ help
+ This option enables the system-wide support for task boosting.
+ When this support is enabled a new sysctl interface is exposed to
+ user-space via:
+ /proc/sys/kernel/sched_cfs_boost
+ which allows to set a system-wide boost value in range [0..100].
+
+ The currently boosting strategy is implemented in such a way that:
+ - a 0% boost value requires to operate in "standard" mode by
+ scheduling all tasks at the minimum capacities required by their
+ workload demand
+ - a 100% boost value requires to push at maximum the task
+ performances, "regardless" of the incurred energy consumption
+
+ A boost value in between these two boundaries is used to bias the
+ power/performance trade-off, the higher the boost value the more the
+ scheduler is biased toward performance boosting instead of energy
+ efficiency.
+
+ Since this support exposes a single system-wide knob, the specified
+ boost value is applied to all (CFS) tasks in the system.
+
+ NOTE: SchedTune support is available only on SMP system since only
+ for those systems is currently defined and tracked the utilization
+ signal for RQs and SEs.
+
+ If unsure, say N.
+
config SYSFS_DEPRECATED
bool "Enable deprecated sysfs features to support old userspace tools"
depends on SYSFS
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 5e59b83..26ab2a6 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o
obj-$(CONFIG_SCHED_AUTOGROUP) += auto_group.o
obj-$(CONFIG_SCHEDSTATS) += stats.o
obj-$(CONFIG_SCHED_DEBUG) += debug.o
+obj-$(CONFIG_SCHED_TUNE) += tune.o
obj-$(CONFIG_CGROUP_CPUACCT) += cpuacct.o
obj-$(CONFIG_CPU_FREQ) += cpufreq.o
obj-$(CONFIG_CPU_FREQ_GOV_SCHEDUTIL) += cpufreq_schedutil.o
diff --git a/kernel/sched/tune.c b/kernel/sched/tune.c
new file mode 100644
index 0000000..7336118
--- /dev/null
+++ b/kernel/sched/tune.c
@@ -0,0 +1,23 @@
+/*
+ * Scheduler Tunability (SchedTune) Extensions for CFS
+ *
+ * Copyright (C) 2016 ARM Ltd, Patrick Bellasi <patrick.bellasi@....com>
+ */
+
+#include "sched.h"
+
+unsigned int sysctl_sched_cfs_boost __read_mostly;
+
+int
+sysctl_sched_cfs_boost_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+ if (ret || !write)
+ return ret;
+
+ return 0;
+}
+
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 739fb17..43b6d14 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -442,6 +442,17 @@ static struct ctl_table kern_table[] = {
.extra1 = &one,
},
#endif
+#ifdef CONFIG_SCHED_TUNE
+ {
+ .procname = "sched_cfs_boost",
+ .data = &sysctl_sched_cfs_boost,
+ .maxlen = sizeof(sysctl_sched_cfs_boost),
+ .mode = 0644,
+ .proc_handler = &sysctl_sched_cfs_boost_handler,
+ .extra1 = &zero,
+ .extra2 = &one_hundred,
+ },
+#endif
#ifdef CONFIG_PROVE_LOCKING
{
.procname = "prove_locking",
--
2.10.1
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