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From: Mike Galbraith on 11 Mar 2010 05:00

sched: remove FAIR_SLEEPERS feature

Our preemption model relies too heavily on sleeper fairness to disable it
without dire consequences. Remove the feature, and save a branch or two.

Signed-off-by: Mike Galbraith <efault(a)gmx.de>
Cc: Ingo Molnar <mingo(a)elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra(a)chello.nl>
LKML-Reference: <new-submission>

---
kernel/sched_fair.c | 2 +-
kernel/sched_features.h | 7 -------
2 files changed, 1 insertion(+), 8 deletions(-)

Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -737,7 +737,7 @@ place_entity(struct cfs_rq *cfs_rq, stru
vruntime += sched_vslice(cfs_rq, se);

/* sleeps up to a single latency don't count. */
- if (!initial && sched_feat(FAIR_SLEEPERS)) {
+ if (!initial) {
unsigned long thresh = sysctl_sched_latency;

/*
Index: linux-2.6/kernel/sched_features.h
===================================================================
--- linux-2.6.orig/kernel/sched_features.h
+++ linux-2.6/kernel/sched_features.h
@@ -1,11 +1,4 @@
/*
- * Disregards a certain amount of sleep time (sched_latency_ns) and
- * considers the task to be running during that period. This gives it
- * a service deficit on wakeup, allowing it to run sooner.
- */
-SCHED_FEAT(FAIR_SLEEPERS, 1)
-
-/*
* Only give sleepers 50% of their service deficit. This allows
* them to run sooner, but does not allow tons of sleepers to
* rip the spread apart.


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