[PATCH] improve precision of idle time detection.
Increase the precision of the idle time calculation that is exported
to user space via /sys/devices/system/cpu/cpu<x>/idle_time_us
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 6fc7854..3979a6f 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -851,9 +851,11 @@
unsigned long long idle_count;
idle = &per_cpu(s390_idle, dev->id);
- spin_lock_irq(&idle->lock);
+ spin_lock(&idle->lock);
idle_count = idle->idle_count;
- spin_unlock_irq(&idle->lock);
+ if (idle->idle_enter)
+ idle_count++;
+ spin_unlock(&idle->lock);
return sprintf(buf, "%llu\n", idle_count);
}
static SYSDEV_ATTR(idle_count, 0444, show_idle_count, NULL);
@@ -862,18 +864,17 @@
struct sysdev_attribute *attr, char *buf)
{
struct s390_idle_data *idle;
- unsigned long long new_time;
+ unsigned long long now, idle_time, idle_enter;
idle = &per_cpu(s390_idle, dev->id);
- spin_lock_irq(&idle->lock);
- if (idle->in_idle) {
- new_time = get_clock();
- idle->idle_time += new_time - idle->idle_enter;
- idle->idle_enter = new_time;
- }
- new_time = idle->idle_time;
- spin_unlock_irq(&idle->lock);
- return sprintf(buf, "%llu\n", new_time >> 12);
+ spin_lock(&idle->lock);
+ now = get_clock();
+ idle_time = idle->idle_time;
+ idle_enter = idle->idle_enter;
+ if (idle_enter != 0ULL && idle_enter < now)
+ idle_time += now - idle_enter;
+ spin_unlock(&idle->lock);
+ return sprintf(buf, "%llu\n", idle_time >> 12);
}
static SYSDEV_ATTR(idle_time_us, 0444, show_idle_time, NULL);