[PATCH] cpufreq: ondemand: account iowait as idle time

From: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>

This patch changes the idle time accounting in ondemand governor.
With this patch ondemand governor accounts cpu iowait time as idle time.

Thanks to Stefan Seyfried for identifying this issue.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/cpufreq/cpufreq_ondemand.c

@@ -221,6 +221,7 @@ static struct attribute_group dbs_attr_group = {
 static void dbs_check_cpu(int cpu)
 {
 	unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
+	unsigned int total_idle_ticks;
 	unsigned int freq_down_step;
 	unsigned int freq_down_sampling_rate;
 	static int down_skip[NR_CPUS];
@@ -244,9 +245,11 @@ static void dbs_check_cpu(int cpu)
 	 * 5% of max_frequency 
 	 */
 	/* Check for frequency increase */
-	idle_ticks = kstat_cpu(cpu).cpustat.idle - 
+	total_idle_ticks = kstat_cpu(cpu).cpustat.idle +
+		kstat_cpu(cpu).cpustat.iowait;
+	idle_ticks = total_idle_ticks -
 		this_dbs_info->prev_cpu_idle_up;
-	this_dbs_info->prev_cpu_idle_up = kstat_cpu(cpu).cpustat.idle;
+	this_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 
 	/* Scale idle ticks by 100 and compare with up and down ticks */
 	idle_ticks *= 100;
@@ -258,7 +261,7 @@ static void dbs_check_cpu(int cpu)
 			this_dbs_info->cur_policy->max, 
 			CPUFREQ_RELATION_H);
 		down_skip[cpu] = 0;
-		this_dbs_info->prev_cpu_idle_down = kstat_cpu(cpu).cpustat.idle;
+		this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 		return;
 	}
 
@@ -267,12 +270,12 @@ static void dbs_check_cpu(int cpu)
 	if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
 		return;
 
-	idle_ticks = kstat_cpu(cpu).cpustat.idle - 
+	idle_ticks = total_idle_ticks -
 		this_dbs_info->prev_cpu_idle_down;
 	/* Scale idle ticks by 100 and compare with up and down ticks */
 	idle_ticks *= 100;
 	down_skip[cpu] = 0;
-	this_dbs_info->prev_cpu_idle_down = kstat_cpu(cpu).cpustat.idle;
+	this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 
 	freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 		dbs_tuners_ins.sampling_down_factor;
@@ -342,9 +345,11 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 		this_dbs_info->cur_policy = policy;
 		
 		this_dbs_info->prev_cpu_idle_up = 
-				kstat_cpu(cpu).cpustat.idle;
+				kstat_cpu(cpu).cpustat.idle +
+				kstat_cpu(cpu).cpustat.iowait;
 		this_dbs_info->prev_cpu_idle_down = 
-				kstat_cpu(cpu).cpustat.idle;
+				kstat_cpu(cpu).cpustat.idle +
+				kstat_cpu(cpu).cpustat.iowait;
 		this_dbs_info->enable = 1;
 		sysfs_create_group(&policy->kobj, &dbs_attr_group);
 		dbs_enable++;