time: track accurate idle time with tick_sched.idle_sleeptime
Current idle time in kstat is based on jiffies and is coarse grained.
tick_sched.idle_sleeptime is making some attempt to keep track of idle time
in a fine grained manner. But, it is not handling the time spent in
interrupts fully.
Make tick_sched.idle_sleeptime accurate with respect to time spent on
handling interrupts and also add tick_sched.idle_lastupdate, which keeps
track of last time when idle_sleeptime was updated.
This statistics will be crucial for cpufreq-ondemand governor, which can
shed some conservative gaurd band that is uses today while setting the
frequency. The ondemand changes that uses the exact idle time is coming
soon.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 8fe1ff4..d7837d4 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -280,9 +280,14 @@
*/
void irq_enter(void)
{
+#ifdef CONFIG_NO_HZ
+ int cpu = smp_processor_id();
+ if (idle_cpu(cpu) && !in_interrupt())
+ tick_nohz_stop_idle(cpu);
+#endif
__irq_enter();
#ifdef CONFIG_NO_HZ
- if (idle_cpu(smp_processor_id()))
+ if (idle_cpu(cpu))
tick_nohz_update_jiffies();
#endif
}