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authorIngo Molnar <mingo@elte.hu>2009-09-16 08:54:45 +0200
committerIngo Molnar <mingo@elte.hu>2009-09-16 09:05:20 +0200
commit51e0304ce6e55a6e59658558916b4f74da085ff0 (patch)
treeda17f8f9f1b3b0431cd0cd1e90ea95f970654f9f
parent59abf02644c45f1591e1374ee7bb45dc757fcb88 (diff)
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sched: Implement a gentler fair-sleepers feature
Add back FAIR_SLEEPERS and GENTLE_FAIR_SLEEPERS. FAIR_SLEEPERS is the old logic: credit sleepers with their sleep time. GENTLE_FAIR_SLEEPERS dampens this a bit: 50% of their sleep time gets credited. The hope here is to still give the benefits of fair-sleepers logic (quick wakeups, etc.) while not allow them to have 100% of their sleep time as if they were running. Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/sched_fair.c9
-rw-r--r--kernel/sched_features.h9
2 files changed, 16 insertions, 2 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a37f311..acf16a8 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -711,7 +711,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
if (!initial) {
/* sleeps upto a single latency don't count. */
- if (sched_feat(NEW_FAIR_SLEEPERS)) {
+ if (sched_feat(FAIR_SLEEPERS)) {
unsigned long thresh = sysctl_sched_latency;
/*
@@ -725,6 +725,13 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
task_of(se)->policy != SCHED_IDLE))
thresh = calc_delta_fair(thresh, se);
+ /*
+ * Halve their sleep time's effect, to allow
+ * for a gentler effect of sleepers:
+ */
+ if (sched_feat(GENTLE_FAIR_SLEEPERS))
+ thresh >>= 1;
+
vruntime -= thresh;
}
}
diff --git a/kernel/sched_features.h b/kernel/sched_features.h
index 70115c6..fd37567 100644
--- a/kernel/sched_features.h
+++ b/kernel/sched_features.h
@@ -3,7 +3,14 @@
* considers the task to be running during that period. This gives it
* a service deficit on wakeup, allowing it to run sooner.
*/
-SCHED_FEAT(NEW_FAIR_SLEEPERS, 0)
+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.
+ */
+SCHED_FEAT(GENTLE_FAIR_SLEEPERS, 1)
/*
* By not normalizing the sleep time, heavy tasks get an effective