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.

Change-Id: I59a41725e2d8f9238a61dfb0c909071b53560fc0
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Git-commit: 63c8fad2b06805ef88f1220551289f0a3c3529f1
Git-repo: https://source.codeaurora.org/quic/la/kernel/msm-4.4
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 861f715a673d..9fe71c774543 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -121,6 +121,22 @@ 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