Re: [RFC][PATCH 5/7] cpufreq / sched: UUF_IO flag to indicate iowait condition

[Rafael J. Wysocki]

On Tue, Aug 2, 2016 at 3:22 AM, Steve Muckle <steve.muckle@xxxxxxxxxx> wrote:
> On Mon, Aug 01, 2016 at 01:37:23AM +0200, Rafael J. Wysocki wrote:
> ...
>> For this purpose, define a new cpufreq_update_util() flag
>> UUF_IO and modify enqueue_task_fair() to pass that flag to
>> cpufreq_update_util() in the in_iowait case.  That generally
>> requires cpufreq_update_util() to be called directly from there,
>> because update_load_avg() is not likely to be invoked in that
>> case.
>
> I didn't follow why the cpufreq hook won't likely be called if
> in_iowait is set? AFAICS update_load_avg() gets called in the second loop
> and calls update_cfs_rq_load_avg (triggers the hook).

In practice it turns out that in the majority of cases when in_iowait
is set the second loop will not run.

Thanks,
Rafael