GIT: unionfs2-2.6.27.y: sched: wakeup preempt when small overlap
Erez Zadok
ezk at fsl.cs.sunysb.edu
Thu Aug 12 23:15:09 EDT 2010
commit ecfb7fb9b13c617447a7f6b5925da26798c1a8a1
Author: Peter Zijlstra <a.p.zijlstra at chello.nl>
Date: Sat Sep 20 23:38:02 2008 +0200
sched: wakeup preempt when small overlap
commit 15afe09bf496ae10c989e1a375a6b5da7bd3e16e upstream.
Lin Ming reported a 10% OLTP regression against 2.6.27-rc4.
The difference seems to come from different preemption agressiveness,
which affects the cache footprint of the workload and its effective
cache trashing.
Aggresively preempt a task if its avg overlap is very small, this should
avoid the task going to sleep and find it still running when we schedule
back to it - saving a wakeup.
Reported-by: Lin Ming <ming.m.lin at intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra at chello.nl>
Signed-off-by: Ingo Molnar <mingo at elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 20d6dd5..6d32974 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -901,7 +901,7 @@ struct sched_class {
void (*yield_task) (struct rq *rq);
int (*select_task_rq)(struct task_struct *p, int sync);
- void (*check_preempt_curr) (struct rq *rq, struct task_struct *p);
+ void (*check_preempt_curr) (struct rq *rq, struct task_struct *p, int sync);
struct task_struct * (*pick_next_task) (struct rq *rq);
void (*put_prev_task) (struct rq *rq, struct task_struct *p);
diff --git a/kernel/sched.c b/kernel/sched.c
index 98c0cdc..f01ff16 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -604,9 +604,9 @@ struct rq {
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
-static inline void check_preempt_curr(struct rq *rq, struct task_struct *p)
+static inline void check_preempt_curr(struct rq *rq, struct task_struct *p, int sync)
{
- rq->curr->sched_class->check_preempt_curr(rq, p);
+ rq->curr->sched_class->check_preempt_curr(rq, p, sync);
}
static inline int cpu_of(struct rq *rq)
@@ -2285,7 +2285,7 @@ out_running:
trace_mark(kernel_sched_wakeup,
"pid %d state %ld ## rq %p task %p rq->curr %p",
p->pid, p->state, rq, p, rq->curr);
- check_preempt_curr(rq, p);
+ check_preempt_curr(rq, p, sync);
p->state = TASK_RUNNING;
#ifdef CONFIG_SMP
@@ -2420,7 +2420,7 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
trace_mark(kernel_sched_wakeup_new,
"pid %d state %ld ## rq %p task %p rq->curr %p",
p->pid, p->state, rq, p, rq->curr);
- check_preempt_curr(rq, p);
+ check_preempt_curr(rq, p, 0);
#ifdef CONFIG_SMP
if (p->sched_class->task_wake_up)
p->sched_class->task_wake_up(rq, p);
@@ -2880,7 +2880,7 @@ static void pull_task(struct rq *src_rq, struct task_struct *p,
* Note that idle threads have a prio of MAX_PRIO, for this test
* to be always true for them.
*/
- check_preempt_curr(this_rq, p);
+ check_preempt_curr(this_rq, p, 0);
}
/*
@@ -5957,7 +5957,7 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
set_task_cpu(p, dest_cpu);
if (on_rq) {
activate_task(rq_dest, p, 0);
- check_preempt_curr(rq_dest, p);
+ check_preempt_curr(rq_dest, p, 0);
}
done:
ret = 1;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index fb8994c..ab8e6f3 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1331,7 +1331,7 @@ static inline int depth_se(struct sched_entity *se)
/*
* Preempt the current task with a newly woken task if needed:
*/
-static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
+static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
{
struct task_struct *curr = rq->curr;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
@@ -1360,6 +1360,13 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
if (!sched_feat(WAKEUP_PREEMPT))
return;
+ if (sched_feat(WAKEUP_OVERLAP) && sync &&
+ se->avg_overlap < sysctl_sched_migration_cost &&
+ pse->avg_overlap < sysctl_sched_migration_cost) {
+ resched_task(curr);
+ return;
+ }
+
/*
* preemption test can be made between sibling entities who are in the
* same cfs_rq i.e who have a common parent. Walk up the hierarchy of
@@ -1642,7 +1649,7 @@ static void prio_changed_fair(struct rq *rq, struct task_struct *p,
if (p->prio > oldprio)
resched_task(rq->curr);
} else
- check_preempt_curr(rq, p);
+ check_preempt_curr(rq, p, 0);
}
/*
@@ -1659,7 +1666,7 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p,
if (running)
resched_task(rq->curr);
else
- check_preempt_curr(rq, p);
+ check_preempt_curr(rq, p, 0);
}
/* Account for a task changing its policy or group.
diff --git a/kernel/sched_features.h b/kernel/sched_features.h
index c4c88ae..4e51893 100644
--- a/kernel/sched_features.h
+++ b/kernel/sched_features.h
@@ -11,3 +11,4 @@ SCHED_FEAT(ASYM_GRAN, 1)
SCHED_FEAT(LB_BIAS, 1)
SCHED_FEAT(LB_WAKEUP_UPDATE, 1)
SCHED_FEAT(ASYM_EFF_LOAD, 1)
+SCHED_FEAT(WAKEUP_OVERLAP, 1)
diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index 3a4f92d..dec4cca 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -14,7 +14,7 @@ static int select_task_rq_idle(struct task_struct *p, int sync)
/*
* Idle tasks are unconditionally rescheduled:
*/
-static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p)
+static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int sync)
{
resched_task(rq->idle);
}
@@ -76,7 +76,7 @@ static void switched_to_idle(struct rq *rq, struct task_struct *p,
if (running)
resched_task(rq->curr);
else
- check_preempt_curr(rq, p);
+ check_preempt_curr(rq, p, 0);
}
static void prio_changed_idle(struct rq *rq, struct task_struct *p,
@@ -93,7 +93,7 @@ static void prio_changed_idle(struct rq *rq, struct task_struct *p,
if (p->prio > oldprio)
resched_task(rq->curr);
} else
- check_preempt_curr(rq, p);
+ check_preempt_curr(rq, p, 0);
}
/*
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 37f0721..68c4745 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -784,7 +784,7 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
/*
* Preempt the current task with a newly woken task if needed:
*/
-static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
+static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int sync)
{
if (p->prio < rq->curr->prio) {
resched_task(rq->curr);
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