2009-11-24 11:12:11

by Tim Blechmann

[permalink] [raw]

Subject: [PATCH 2/5] sched.c: change branch hint

---

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

10420275 170645395 94 context_switch sched.c
3043
10408421 171098521 94 context_switch sched.c
3050

Signed-off-by: Tim Blechmann <[email protected]>
---
kernel/sched.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index c78dcfe..2a78b38 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3040,14 +3040,14 @@ context_switch(struct rq *rq, struct task_struct
*prev,
*/
arch_start_context_switch(prev);
- if (unlikely(!mm)) {
+ if (likely(!mm)) {
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);
enter_lazy_tlb(oldmm, next);
} else
switch_mm(oldmm, mm, next);
- if (unlikely(!prev->mm)) {
+ if (likely(!prev->mm)) {
prev->active_mm = NULL;
rq->prev_mm = oldmm;
}
--
1.6.4.2

---

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2009-11-24 16:57:55

by Tim Blechmann

[permalink] [raw]

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

---

Commit-ID: 710390d90f143a9ebb87a475215140f426792efd
Gitweb: http://git.kernel.org/tip/710390d90f143a9ebb87a475215140f426792efd
Author: Tim Blechmann <[email protected]>
AuthorDate: Tue, 24 Nov 2009 11:55:27 +0100
Committer: Ingo Molnar <[email protected]>
CommitDate: Tue, 24 Nov 2009 12:18:42 +0100

sched: Optimize branch hint in context_switch()

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

10420275 170645395 94 context_switch sched.c
3043
10408421 171098521 94 context_switch sched.c
3050

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.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 93474a7..010d5e1 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2829,14 +2829,14 @@ context_switch(struct rq *rq, struct task_struct *prev,
*/
arch_start_context_switch(prev);

- if (unlikely(!mm)) {
+ if (likely(!mm)) {
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);
enter_lazy_tlb(oldmm, next);
} else
switch_mm(oldmm, mm, next);

- if (unlikely(!prev->mm)) {
+ if (likely(!prev->mm)) {
prev->active_mm = NULL;
rq->prev_mm = oldmm;
}