[tip:sched/core] sched: Optimize cgroup vs wakeup a bit

tip-bot for Peter Zijlstra
2009-09-16T15:10:24Z

Commit-ID: 3b6408942206f940dd538e980e9904e48f4b64f8
Gitweb: http://git.kernel.org/tip/3b6408942206f940dd538e980e9904e48f4b64f8
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Wed, 16 Sep 2009 13:44:33 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 16 Sep 2009 16:44:32 +0200

sched: Optimize cgroup vs wakeup a bit

We don't need to call update_shares() for each domain we iterate,
just got the largets one.

However, we should call it before wake_affine() as well, so that
that can use up-to-date values too.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
kernel/sched.c | 7 -------
kernel/sched_fair.c | 23 +++++++++--------------
kernel/sched_features.h | 2 +-
3 files changed, 10 insertions(+), 22 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index af04ede..5049d95 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -376,13 +376,6 @@ static inline void set_task_rq(struct task_struct *p, unsigned int cpu)

#else

-#ifdef CONFIG_SMP
-static int root_task_group_empty(void)
-{
- return 1;
-}
-#endif
-
static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { }
static inline struct task_group *task_group(struct task_struct *p)
{
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index acf16a8..722d392 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1348,7 +1348,7 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
*/
static int select_task_rq_fair(struct task_struct *p, int sd_flag, int flags)
{
- struct sched_domain *tmp, *sd = NULL;
+ struct sched_domain *tmp, *shares = NULL, *sd = NULL;
int cpu = smp_processor_id();
int prev_cpu = task_cpu(p);
int new_cpu = cpu;
@@ -1387,22 +1387,14 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int flags)
break;
}

- switch (sd_flag) {
- case SD_BALANCE_WAKE:
- if (!sched_feat(LB_WAKEUP_UPDATE))
- break;
- case SD_BALANCE_FORK:
- case SD_BALANCE_EXEC:
- if (root_task_group_empty())
- break;
- update_shares(tmp);
- default:
- break;
- }
-
if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {

+ if (sched_feat(LB_SHARES_UPDATE)) {
+ update_shares(tmp);
+ shares = tmp;
+ }
+
if (wake_affine(tmp, p, sync)) {
new_cpu = cpu;
goto out;
@@ -1417,6 +1409,9 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int flags)
sd = tmp;
}

+ if (sd && sd != shares && sched_feat(LB_SHARES_UPDATE))
+ update_shares(sd);
+
while (sd) {
struct sched_group *group;
int weight;
diff --git a/kernel/sched_features.h b/kernel/sched_features.h
index fd37567..d5059fd 100644
--- a/kernel/sched_features.h
+++ b/kernel/sched_features.h
@@ -107,7 +107,7 @@ SCHED_FEAT(ARCH_POWER, 0)
SCHED_FEAT(HRTICK, 0)
SCHED_FEAT(DOUBLE_TICK, 0)
SCHED_FEAT(LB_BIAS, 1)
-SCHED_FEAT(LB_WAKEUP_UPDATE, 1)
+SCHED_FEAT(LB_SHARES_UPDATE, 1)
SCHED_FEAT(ASYM_EFF_LOAD, 1)

/*