[RFC PATCH 11/11] sched: fair sleepers for timer and interactive

[Mathieu Desnoyers]

Add FAIR_SLEEPERS_TIMER and FAIR_SLEEPERS_INTERACTIVE tuning knobs.

Turning off FAIR_SLEEPERS and turning on FAIR_SLEEPERS_INTERACTIVE does a pretty
good job for interactivity.

Setting FAIR_SLEEPERS to off helps keeping the min_vruntime value somewhere
between MIN_vruntime and max_vruntime rather than somewhere at the right of all
running threads.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
---
 kernel/sched_fair.c     |    5 ++++-
 kernel/sched_features.h |    4 +++-
 2 files changed, 7 insertions(+), 2 deletions(-)

Index: linux-2.6-lttng.git/kernel/sched_fair.c
===================================================================
--- linux-2.6-lttng.git.orig/kernel/sched_fair.c
+++ linux-2.6-lttng.git/kernel/sched_fair.c
@@ -748,7 +748,10 @@ place_entity(struct cfs_rq *cfs_rq, stru
 		vruntime += sched_vslice(cfs_rq, se);
 
 	/* sleeps up to a single latency don't count. */
-	if (sched_feat(FAIR_SLEEPERS) && !initial) {
+	if (!initial
+	    && (sched_feat(FAIR_SLEEPERS)
+	       || (sched_feat(FAIR_SLEEPERS_TIMER) && se->timer)
+	       || (sched_feat(FAIR_SLEEPERS_INTERACTIVE) && se->interactive))) {
 		unsigned long thresh = sysctl_sched_latency;
 
 		/*
Index: linux-2.6-lttng.git/kernel/sched_features.h
===================================================================
--- linux-2.6-lttng.git.orig/kernel/sched_features.h
+++ linux-2.6-lttng.git/kernel/sched_features.h
@@ -3,7 +3,9 @@
  * them to run sooner, but does not allow tons of sleepers to
  * rip the spread apart.
  */
-SCHED_FEAT(FAIR_SLEEPERS, 1)
+SCHED_FEAT(FAIR_SLEEPERS, 1)		 /* Apply to all wakeups */
+SCHED_FEAT(FAIR_SLEEPERS_INTERACTIVE, 0) /* Selects interactive wakeups */
+SCHED_FEAT(FAIR_SLEEPERS_TIMER, 0)	 /* Selects timer-driven wakeups */
 SCHED_FEAT(GENTLE_FAIR_SLEEPERS, 1)
 
 /*

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