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authorPatrick Bellasi <patrick.bellasi@arm.com>2015-06-22 18:11:44 +0100
committerGuodong Xu <guodong.xu@linaro.org>2017-06-06 14:24:15 +0800
commit336a061c89999aed8ddf6416b3e1f34e14e4fdb4 (patch)
tree09e03ca77c17251faa448410f4b1776d86ad5f7d
parent3f2e524add76e676e3e830c721a67702e70f56b6 (diff)
downloadarm64-stable-rc-336a061c89999aed8ddf6416b3e1f34e14e4fdb4.tar.gz
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@redhat.com> cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
-rw-r--r--include/linux/sched/sysctl.h16
-rw-r--r--init/Kconfig26
-rw-r--r--kernel/sched/Makefile1
-rw-r--r--kernel/sched/tune.c16
-rw-r--r--kernel/sysctl.c11
5 files changed, 70 insertions, 0 deletions
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index c9e4731cf10b..4479e48c7712 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 235c7a2c0d20..83d8c02e7a57 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1237,6 +1237,32 @@ 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 0eabc9db4c3d..c6a85f813dfd 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 000000000000..a93af9c2f267
--- /dev/null
+++ b/kernel/sched/tune.c
@@ -0,0 +1,16 @@
+#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 300d64162aff..9da7012553dc 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -435,6 +435,17 @@ 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",