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From: tip-bot for Mike Galbraith on 11 Mar 2010 13:40
Commit-ID: 13814d42e45dfbe845a0bbe5184565d9236896ae
Gitweb: http://git.kernel.org/tip/13814d42e45dfbe845a0bbe5184565d9236896ae
Author: Mike Galbraith <efault(a)gmx.de>
AuthorDate: Thu, 11 Mar 2010 17:17:04 +0100
Committer: Ingo Molnar <mingo(a)elte.hu>
CommitDate: Thu, 11 Mar 2010 18:32:53 +0100

sched: Remove ASYM_GRAN feature

This features has been enabled for quite a while, after testing showed that
easing preemption for light tasks was harmful to high priority threads.

Remove the feature flag.

Signed-off-by: Mike Galbraith <efault(a)gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra(a)chello.nl>
LKML-Reference: <1268301675.6785.44.camel(a)marge.simson.net>
Signed-off-by: Ingo Molnar <mingo(a)elte.hu>
---
kernel/sched_fair.c | 28 +++++++++++-----------------
kernel/sched_features.h | 6 ------
2 files changed, 11 insertions(+), 23 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 1d99535..9357ecd 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1583,24 +1583,18 @@ wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
/*
* Since its curr running now, convert the gran from real-time
* to virtual-time in his units.
+ *
+ * By using 'se' instead of 'curr' we penalize light tasks, so
+ * they get preempted easier. That is, if 'se' < 'curr' then
+ * the resulting gran will be larger, therefore penalizing the
+ * lighter, if otoh 'se' > 'curr' then the resulting gran will
+ * be smaller, again penalizing the lighter task.
+ *
+ * This is especially important for buddies when the leftmost
+ * task is higher priority than the buddy.
*/
- if (sched_feat(ASYM_GRAN)) {
- /*
- * By using 'se' instead of 'curr' we penalize light tasks, so
- * they get preempted easier. That is, if 'se' < 'curr' then
- * the resulting gran will be larger, therefore penalizing the
- * lighter, if otoh 'se' > 'curr' then the resulting gran will
- * be smaller, again penalizing the lighter task.
- *
- * This is especially important for buddies when the leftmost
- * task is higher priority than the buddy.
- */
- if (unlikely(se->load.weight != NICE_0_LOAD))
- gran = calc_delta_fair(gran, se);
- } else {
- if (unlikely(curr->load.weight != NICE_0_LOAD))
- gran = calc_delta_fair(gran, curr);
- }
+ if (unlikely(se->load.weight != NICE_0_LOAD))
+ gran = calc_delta_fair(gran, se);

return gran;
}
diff --git a/kernel/sched_features.h b/kernel/sched_features.h
index f54b6f9..83c66e8 100644
--- a/kernel/sched_features.h
+++ b/kernel/sched_features.h
@@ -17,12 +17,6 @@ SCHED_FEAT(START_DEBIT, 1)
SCHED_FEAT(WAKEUP_PREEMPT, 1)

/*
- * When converting the wakeup granularity to virtual time, do it such
- * that heavier tasks preempting a lighter task have an edge.
- */
-SCHED_FEAT(ASYM_GRAN, 1)
-
-/*
* Based on load and program behaviour, see if it makes sense to place
* a newly woken task on the same cpu as the task that woke it --
* improve cache locality. Typically used with SYNC wakeups as
--
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