linux-kernel - [PATCH] cpufreq: ondemand: Don't synchronize sample rate unless mulitple cpus present

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Message-Id: <1263348870-2269-1-git-send-email-mike@android.com>
Date:	Tue, 12 Jan 2010 18:14:30 -0800
From:	Mike Chan <mike@...roid.com>
To:	cpufreq@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Jocelyn Falempe <jocelyn.falempe@...orola.com>,
	Mike Chan <mike@...roid.com>
Subject: [PATCH] cpufreq: ondemand: Don't synchronize sample rate unless mulitple cpus present

From: Jocelyn Falempe <jocelyn.falempe@...orola.com>

For UP systems this is not required, and results in a more consistent
sample interval.

Signed-off-by: Jocelyn Falempe <jocelyn.falempe@...orola.com>
Signed-off-by: Mike Chan <mike@...roid.com>
---
 drivers/cpufreq/cpufreq_ondemand.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 4b34ade..d139558 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -576,7 +576,9 @@ static void do_dbs_timer(struct work_struct *work)
 	/* We want all CPUs to do sampling nearly on same jiffy */
 	int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 
-	delay -= jiffies % delay;
+	if (num_online_cpus() > 1)
+		delay -= jiffies % delay;
+
 	mutex_lock(&dbs_info->timer_mutex);
 
 	/* Common NORMAL_SAMPLE setup */
@@ -601,7 +603,9 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 {
 	/* We want all CPUs to do sampling nearly on same jiffy */
 	int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
-	delay -= jiffies % delay;
+
+	if (num_online_cpus() > 1)
+ 		delay -= jiffies % delay;
 
 	dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 	INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
-- 
1.6.6

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