Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks

[Rafael J. Wysocki]

On Wed, Feb 10, 2016 at 11:07 PM, Steve Muckle <steve.muckle@xxxxxxxxxx> wrote:
> On 02/10/2016 01:49 PM, Rafael J. Wysocki wrote:
>>>> If done this way, I guess we may pass rq_clock_task(rq) as the time
>>>> >> arg to cpufreq_update_util() from there and then the cpu_lock() call
>>>> >> I've added to this prototype won't be necessary any more.
>>> >
>>> > Is it rq_clock_task() or rq_clock()? The former can omit irq time so may
>>> > gradually fall behind wall clock time, delaying callbacks in cpufreq.
>>
>> What matters to us is the difference between the current time and the
>> time we previously took a sample and there shouldn't be too much
>> difference between the two in that respect.
>
> Sorry, the reference to wall clock time was unnecessary. I just meant it
> can lose time, which could cause cpufreq updates to be delayed during
> irq heavy periods.
>
>> Both are good enough IMO, but I can update the patch to use rq_clock()
>> if that's preferred.
>
> I do believe rq_clock should be used as workloads such as heavy
> networking could spend a significant portion of time in interrupts,
> skewing rq_clock_task significantly, assuming I understand it correctly.

OK, I'll send an update, then.

Thanks,
Rafael