linux-kernel - [PATCH V2 Resend 2/4] timer: hrtimer: Don't check idle_cpu() before calling get_nohz_timer

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Message-Id: <5caa3dab5feb7cc3d78b4f9a19dbb24401796b53.1352196505.git.viresh.kumar@linaro.org>
Date:	Tue,  6 Nov 2012 16:08:44 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	pjt@...gle.com, paul.mckenney@...aro.org, tglx@...utronix.de,
	tj@...nel.org, suresh.b.siddha@...el.com, venki@...gle.com,
	mingo@...hat.com, peterz@...radead.org, rostedt@...dmis.org
Cc:	Arvind.Chauhan@....com, linaro-dev@...ts.linaro.org,
	patches@...aro.org, pdsw-power-team@....com,
	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: [PATCH V2 Resend 2/4] timer: hrtimer: Don't check idle_cpu() before calling get_nohz_timer_target()

Check for current cpu's idleness already done in implementation of
sched_select_cpu() which is called by get_nohz_timer_target(). So, no need to
call idle_cpu() twice, once from sched_select_cpu() and once from timer and
hrtimer before calling get_nohz_timer_target().

This patch removes calls to idle_cpu() from timer and hrtimer.

This also reduces an extra call to smp_processor_id() when
get_nohz_timer_target() is called.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 kernel/hrtimer.c | 2 +-
 kernel/timer.c   | 8 +++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 6db7a5e..74bdaf6 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -159,7 +159,7 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
 static int hrtimer_get_target(int this_cpu, int pinned)
 {
 #ifdef CONFIG_NO_HZ
-	if (!pinned && get_sysctl_timer_migration() && idle_cpu(this_cpu))
+	if (!pinned && get_sysctl_timer_migration())
 		return get_nohz_timer_target();
 #endif
 	return this_cpu;
diff --git a/kernel/timer.c b/kernel/timer.c
index 367d008..1170ece 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -735,11 +735,13 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
 
 	debug_activate(timer, expires);
 
-	cpu = smp_processor_id();
-
 #if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
-	if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
+	if (!pinned && get_sysctl_timer_migration())
 		cpu = get_nohz_timer_target();
+	else
+		cpu = smp_processor_id();
+#else
+	cpu = smp_processor_id();
 #endif
 	new_base = per_cpu(tvec_bases, cpu);
 
-- 
1.7.12.rc2.18.g61b472e


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