2009-11-24 11:10:57

by Tim Blechmann

[permalink] [raw]

Subject: [PATCH 4/5] sched_fair.c: remove branch hint

---

branch hint profiling of my nehalem machine, showed 90% incorrect
branch hints:

15728471 158903754 90 pick_next_task_fair sched_fair.c
1555

Signed-off-by: Tim Blechmann <[email protected]>
---
kernel/sched_fair.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index e5945df..5a0965c 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1552,7 +1552,7 @@ static struct task_struct
*pick_next_task_fair(struct rq *rq)
struct cfs_rq *cfs_rq = &rq->cfs;
struct sched_entity *se;
- if (unlikely(!cfs_rq->nr_running))
+ if (!cfs_rq->nr_running)
return NULL;
do {
--
1.6.4.2

---

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2009-11-24 16:57:51

by Tim Blechmann

[permalink] [raw]

Subject: [tip:sched/core] sched: Optimize branch hint in pick_next_task_fair()

---

Commit-ID: 36ace27e3e60d44ea69ce394b2e45386ae98d9d9
Gitweb: http://git.kernel.org/tip/36ace27e3e60d44ea69ce394b2e45386ae98d9d9
Author: Tim Blechmann <[email protected]>
AuthorDate: Tue, 24 Nov 2009 11:55:45 +0100
Committer: Ingo Molnar <[email protected]>
CommitDate: Tue, 24 Nov 2009 12:18:12 +0100

sched: Optimize branch hint in pick_next_task_fair()

Branch hint profiling on my nehalem machine showed 90%
incorrect branch hints:

15728471 158903754 90 pick_next_task_fair
sched_fair.c 1555

Signed-off-by: Tim Blechmann <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sched_fair.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index f28a267..24086e7 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1704,7 +1704,7 @@ static struct task_struct *pick_next_task_fair(struct rq *rq)
struct cfs_rq *cfs_rq = &rq->cfs;
struct sched_entity *se;

- if (unlikely(!cfs_rq->nr_running))
+ if (!cfs_rq->nr_running)
return NULL;

do {