From: Michael Wang <wangyun@linux.vnet.ibm.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>, ingo Molnar <mingo@elte.hu>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH] sched: Accelerate "pick_next_entity" under special condition
Date: Mon, 16 Jan 2012 17:37:02 +0800 [thread overview]
Message-ID: <4F13EFBE.1030002@linux.vnet.ibm.com> (raw)
From: Michael Wang <wangyun@linux.vnet.ibm.com>
We can avoid some useless operation in some special condition.
For example:
If we have "cfs_rq->next" and it can be use, we just return it directly.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
---
kernel/sched/fair.c | 28 +++++++++++++++++-----------
1 files changed, 17 insertions(+), 11 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 84adb2d..9fc2c3c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1295,6 +1295,8 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
+#define ENTITY_PREEMPT_ALLOWED(prev,next) (wakeup_preempt_entity(prev, next) < 1)
+
/*
* Pick the next process, keeping these things in mind, in this order:
* 1) keep things fair between processes/task groups
@@ -1308,29 +1310,33 @@ static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
struct sched_entity *left = se;
/*
- * Avoid running the skip buddy, if running something else can
- * be done without getting too unfair.
+ * Someone really wants this to run. If it's not unfair, run it.
*/
- if (cfs_rq->skip == se) {
- struct sched_entity *second = __pick_next_entity(se);
- if (second && wakeup_preempt_entity(second, left) < 1)
- se = second;
+ if (cfs_rq->next && ENTITY_PREEMPT_ALLOWED(cfs_rq->next, left)) {
+ se = cfs_rq->next;
+ goto out;
}
/*
* Prefer last buddy, try to return the CPU to a preempted task.
*/
- if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
+ if (cfs_rq->last && ENTITY_PREEMPT_ALLOWED(cfs_rq->last, left)) {
se = cfs_rq->last;
+ goto out;
+ }
/*
- * Someone really wants this to run. If it's not unfair, run it.
+ * Avoid running the skip buddy, if running something else can
+ * be done without getting too unfair.
*/
- if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
- se = cfs_rq->next;
+ if (cfs_rq->skip == se) {
+ struct sched_entity *second = __pick_next_entity(se);
+ if (second && ENTITY_PREEMPT_ALLOWED(second, left))
+ se = second;
+ }
+out:
clear_buddies(cfs_rq, se);
-
return se;
}
--
1.7.4.1
next reply other threads:[~2012-01-16 9:37 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-16 9:37 Michael Wang [this message]
2012-01-16 9:50 ` [PATCH] sched: Accelerate "pick_next_entity" under special condition Michael Wang
2012-01-16 9:51 ` Peter Zijlstra
2012-01-16 10:34 ` Michael Wang
2012-01-17 2:36 ` [PATCH v2] " Michael Wang
2012-01-17 2:41 ` Michael Wang
2012-01-17 2:58 ` Xiaotian Feng
2012-01-17 3:04 ` Michael Wang
2012-01-25 15:55 ` Peter Zijlstra
2012-01-26 10:04 ` Ingo Molnar
2012-01-27 1:22 ` Michael Wang
2012-01-27 4:42 ` Cong Wang
2012-01-29 6:32 ` Michael Wang
2012-01-29 16:33 ` Ingo Molnar
2012-01-30 3:18 ` Michael Wang
2012-01-30 3:25 ` Cong Wang
2012-01-30 5:47 ` Michael Wang
2012-07-03 6:34 ` [PATCH] sched: remove useless code in yield_to Michael Wang
2012-07-12 5:45 ` Michael Wang
2012-07-12 14:07 ` Peter Zijlstra
2012-07-12 18:44 ` Mike Galbraith
2012-07-16 2:39 ` Michael Wang
2012-08-17 6:56 ` Michael Wang
2012-08-17 9:43 ` Peter Zijlstra
2012-08-10 3:05 ` Michael Wang
2012-08-10 3:10 ` Michael Wang
2012-08-10 5:52 ` Mike Galbraith
2012-09-04 18:50 ` [tip:sched/core] sched: Remove useless code in yield_to() tip-bot for Michael Wang
2012-01-27 0:56 ` [PATCH v2] sched: Accelerate "pick_next_entity" under special condition Michael Wang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4F13EFBE.1030002@linux.vnet.ibm.com \
--to=wangyun@linux.vnet.ibm.com \
--cc=a.p.zijlstra@chello.nl \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).