linux-kernel - [tip:sched/core] sched/deadline: Don' t balance during wakeup if wakee is pinned

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Date:	Tue, 28 Oct 2014 04:07:57 -0700
From:	tip-bot for Wanpeng Li <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org,
	tglx@...utronix.de, wanpeng.li@...ux.intel.com, mingo@...nel.org,
	hpa@...or.com, torvalds@...ux-foundation.org
Subject: [tip:sched/core] sched/deadline: Don'
 t balance during wakeup if wakee is pinned

Commit-ID:  f4e9d94a5bf60193d45f92b136e3d166be3ec8d5
Gitweb:     http://git.kernel.org/tip/f4e9d94a5bf60193d45f92b136e3d166be3ec8d5
Author:     Wanpeng Li <wanpeng.li@...ux.intel.com>
AuthorDate: Tue, 14 Oct 2014 10:22:40 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 28 Oct 2014 10:48:02 +0100

sched/deadline: Don't balance during wakeup if wakee is pinned

Use nr_cpus_allowed to bail from select_task_rq() when only one cpu
can be used, and saves some cycles for pinned tasks.

Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: http://lkml.kernel.org/r/1413253360-5318-2-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/deadline.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index fab3bf8..2e31a30 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -933,6 +933,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
 	struct task_struct *curr;
 	struct rq *rq;
 
+	if (p->nr_cpus_allowed == 1)
+		goto out;
+
 	if (sd_flag != SD_BALANCE_WAKE)
 		goto out;
 
--
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