sched: Push put_prev_task() into pick_next_task()

In order to avoid having to do put/set on a whole cgroup hierarchy
when we context switch, push the put into pick_next_task() so that
both operations are in the same function. Further changes then allow
us to possibly optimize away redundant work.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1328936700.2476.17.camel@laptop
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2012-02-11 06:05:00 +01:00 committed by Ingo Molnar
parent fed14d45f9
commit 606dba2e28
7 changed files with 55 additions and 34 deletions

View File

@ -2579,18 +2579,11 @@ static inline void schedule_debug(struct task_struct *prev)
schedstat_inc(this_rq(), sched_count);
}
static void put_prev_task(struct rq *rq, struct task_struct *prev)
{
if (prev->on_rq || rq->skip_clock_update < 0)
update_rq_clock(rq);
prev->sched_class->put_prev_task(rq, prev);
}
/*
* Pick up the highest-prio task:
*/
static inline struct task_struct *
pick_next_task(struct rq *rq)
pick_next_task(struct rq *rq, struct task_struct *prev)
{
const struct sched_class *class;
struct task_struct *p;
@ -2600,13 +2593,13 @@ pick_next_task(struct rq *rq)
* the fair class we can call that function directly:
*/
if (likely(rq->nr_running == rq->cfs.h_nr_running)) {
p = fair_sched_class.pick_next_task(rq);
p = fair_sched_class.pick_next_task(rq, prev);
if (likely(p))
return p;
}
for_each_class(class) {
p = class->pick_next_task(rq);
p = class->pick_next_task(rq, prev);
if (p)
return p;
}
@ -2714,8 +2707,10 @@ need_resched:
rq->idle_stamp = 0;
}
put_prev_task(rq, prev);
next = pick_next_task(rq);
if (prev->on_rq || rq->skip_clock_update < 0)
update_rq_clock(rq);
next = pick_next_task(rq, prev);
clear_tsk_need_resched(prev);
clear_preempt_need_resched();
rq->skip_clock_update = 0;
@ -4748,7 +4743,7 @@ static void migrate_tasks(unsigned int dead_cpu)
if (rq->nr_running == 1)
break;
next = pick_next_task(rq);
next = pick_next_task(rq, NULL);
BUG_ON(!next);
next->sched_class->put_prev_task(rq, next);

View File

@ -990,7 +990,7 @@ static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
return rb_entry(left, struct sched_dl_entity, rb_node);
}
struct task_struct *pick_next_task_dl(struct rq *rq)
struct task_struct *pick_next_task_dl(struct rq *rq, struct task_struct *prev)
{
struct sched_dl_entity *dl_se;
struct task_struct *p;
@ -1001,6 +1001,9 @@ struct task_struct *pick_next_task_dl(struct rq *rq)
if (unlikely(!dl_rq->dl_nr_running))
return NULL;
if (prev)
prev->sched_class->put_prev_task(rq, prev);
dl_se = pick_next_dl_entity(rq, dl_rq);
BUG_ON(!dl_se);

View File

@ -4655,7 +4655,8 @@ preempt:
set_last_buddy(se);
}
static struct task_struct *pick_next_task_fair(struct rq *rq)
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
{
struct task_struct *p;
struct cfs_rq *cfs_rq = &rq->cfs;
@ -4664,6 +4665,9 @@ static struct task_struct *pick_next_task_fair(struct rq *rq)
if (!cfs_rq->nr_running)
return NULL;
if (prev)
prev->sched_class->put_prev_task(rq, prev);
do {
se = pick_next_entity(cfs_rq);
set_next_entity(cfs_rq, se);

View File

@ -33,8 +33,12 @@ static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int fl
resched_task(rq->idle);
}
static struct task_struct *pick_next_task_idle(struct rq *rq)
static struct task_struct *
pick_next_task_idle(struct rq *rq, struct task_struct *prev)
{
if (prev)
prev->sched_class->put_prev_task(rq, prev);
schedstat_inc(rq, sched_goidle);
#ifdef CONFIG_SMP
/* Trigger the post schedule to do an idle_enter for CFS */

View File

@ -1310,15 +1310,7 @@ static struct task_struct *_pick_next_task_rt(struct rq *rq)
{
struct sched_rt_entity *rt_se;
struct task_struct *p;
struct rt_rq *rt_rq;
rt_rq = &rq->rt;
if (!rt_rq->rt_nr_running)
return NULL;
if (rt_rq_throttled(rt_rq))
return NULL;
struct rt_rq *rt_rq = &rq->rt;
do {
rt_se = pick_next_rt_entity(rq, rt_rq);
@ -1332,9 +1324,22 @@ static struct task_struct *_pick_next_task_rt(struct rq *rq)
return p;
}
static struct task_struct *pick_next_task_rt(struct rq *rq)
static struct task_struct *
pick_next_task_rt(struct rq *rq, struct task_struct *prev)
{
struct task_struct *p = _pick_next_task_rt(rq);
struct task_struct *p;
struct rt_rq *rt_rq = &rq->rt;
if (!rt_rq->rt_nr_running)
return NULL;
if (rt_rq_throttled(rt_rq))
return NULL;
if (prev)
prev->sched_class->put_prev_task(rq, prev);
p = _pick_next_task_rt(rq);
/* The running task is never eligible for pushing */
if (p)

View File

@ -1105,7 +1105,13 @@ struct sched_class {
void (*check_preempt_curr) (struct rq *rq, struct task_struct *p, int flags);
struct task_struct * (*pick_next_task) (struct rq *rq);
/*
* It is the responsibility of the pick_next_task() method that will
* return the next task to call put_prev_task() on the @prev task or
* something equivalent.
*/
struct task_struct * (*pick_next_task) (struct rq *rq,
struct task_struct *prev);
void (*put_prev_task) (struct rq *rq, struct task_struct *p);
#ifdef CONFIG_SMP

View File

@ -23,16 +23,20 @@ check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
/* we're never preempted */
}
static struct task_struct *pick_next_task_stop(struct rq *rq)
static struct task_struct *
pick_next_task_stop(struct rq *rq, struct task_struct *prev)
{
struct task_struct *stop = rq->stop;
if (stop && stop->on_rq) {
stop->se.exec_start = rq_clock_task(rq);
return stop;
}
if (!stop || !stop->on_rq)
return NULL;
return NULL;
if (prev)
prev->sched_class->put_prev_task(rq, prev);
stop->se.exec_start = rq_clock_task(rq);
return stop;
}
static void