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Message-Id: <1440010044-3402-10-git-send-email-patrick.bellasi@arm.com>
Date: Wed, 19 Aug 2015 19:47:19 +0100
From: Patrick Bellasi <patrick.bellasi@....com>
To: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: [RFC PATCH 09/14] 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.
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 | 26 ++++++++++++++++++++++++++
kernel/sched/Makefile | 1 +
kernel/sched/tune.c | 17 +++++++++++++++++
kernel/sysctl.c | 11 +++++++++++
5 files changed, 71 insertions(+)
create mode 100644 kernel/sched/tune.c
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index c9e4731..4479e48 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -77,6 +77,22 @@ 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 af09b4f..7fa3419 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1220,6 +1220,32 @@ config SCHED_AUTOGROUP
desktop applications. Task group autogeneration is currently based
upon task session.
+config SCHED_TUNE
+ bool "Boosting for CFS tasks (EXPERIMENTAL)"
+ help
+ This option enables the system-wide support for task boosting.
+ When this support is enabled a new sysctl interface is exposed to
+ userspace 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.
+
+ 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 90ed832..f804ef3 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -18,5 +18,6 @@ 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_GOV_SCHED) += cpufreq_sched.o
diff --git a/kernel/sched/tune.c b/kernel/sched/tune.c
new file mode 100644
index 0000000..4c44b1a
--- /dev/null
+++ b/kernel/sched/tune.c
@@ -0,0 +1,17 @@
+#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 19b62b5..2b4673e 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -433,6 +433,17 @@ 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",
--
2.5.0
--
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