Re: regression caused by 08f511fd41c3 ("cpufreq: Reduce cpufreq_update_util() overhead a bit")

Peter Zijlstra
2016-06-17T14:04:03Z

On Fri, Jun 17, 2016 at 06:16:51AM -0700, Paul E. McKenney wrote:
> > Paul, Peter, any ideas about what may be going on here?
>
> Looks to me like this commit moved some code from synchronize_rcu() to
> synchronize_sched(). Assuming that this is a CONFIG_PREEMPT=y system,
> might there have been a decrease in the wakeups from the rcu_preempt
> kthread?

The 'funny' thing is though; those synchronize thingies are only reached
when we change cpufreq policy, so things like:

for i in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor ; do echo performance > $i ; done

Something which is hardly possible when idle. Weird.