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>

1 files changed, 11 insertions, 0 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index dc6858d6639e..827ba256fdad 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -434,6 +434,17 @@ 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",