From b85d0667268320072ccdeb07c27c25b300ab3724 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Sun, 16 Mar 2008 20:03:22 +0100
Subject: [PATCH] sched: introduce SCHED_FEAT_SYNC_WAKEUPS, turn it off
turn off sync wakeups by default. They are not needed anymore - the
buddy logic should be smart enough to keep the system from
overscheduling.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/sched.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index d8456a9ac9af..263e25e10204 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -627,6 +627,7 @@ enum {
SCHED_FEAT_START_DEBIT = 4,
SCHED_FEAT_HRTICK = 8,
SCHED_FEAT_DOUBLE_TICK = 16,
+ SCHED_FEAT_SYNC_WAKEUPS = 32,
};
const_debug unsigned int sysctl_sched_features =
@@ -634,7 +635,8 @@ const_debug unsigned int sysctl_sched_features =
SCHED_FEAT_WAKEUP_PREEMPT * 1 |
SCHED_FEAT_START_DEBIT * 1 |
SCHED_FEAT_HRTICK * 1 |
- SCHED_FEAT_DOUBLE_TICK * 0;
+ SCHED_FEAT_DOUBLE_TICK * 0 |
+ SCHED_FEAT_SYNC_WAKEUPS * 0;
#define sched_feat(x) (sysctl_sched_features & SCHED_FEAT_##x)
@@ -1916,6 +1918,9 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
long old_state;
struct rq *rq;
+ if (!sched_feat(SYNC_WAKEUPS))
+ sync = 0;
+
smp_wmb();
rq = task_rq_lock(p, &flags);
old_state = p->state;
--
2.20.1