Re: [PATCH V3 2/2] sched: idle: IRQ based next prediction for idle period

[Rafael J. Wysocki]

On Tue, Feb 16, 2016 at 5:44 PM, Nicolas Pitre <nicolas.pitre@xxxxxxxxxx> wrote:
> On Tue, 16 Feb 2016, Daniel Lezcano wrote:
>
>> Many IRQs are quiet most of the time, or they tend to come in bursts of
>> fairly equal time intervals within each burst. It is therefore possible
>> to detect those IRQs with stable intervals and guestimate when the next
>> IRQ event is most likely to happen.
>>
>> Examples of such IRQs may include audio related IRQs where the FIFO size
>> and/or DMA descriptor size with the sample rate create stable intervals,
>> block devices during large data transfers, etc.  Even network streaming
>> of multimedia content creates patterns of periodic network interface IRQs
>> in some cases.
>>
>> This patch adds code to compute the mean interval and variance for each IRQ
>> over a window of time intervals between IRQ events. Those statistics can
>> be used to assist cpuidle in selecting the most appropriate sleep state
>> by predicting the most likely time for the next interrupt.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
>
> The math in next_irq_event() is correct even though I think it could be
> done more simply.  But that can be optimized at a later time.
>
> Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx>

Well, I'm likely overlooking something, but how is this going to be
hooked up to the code in idle.c?

Thanks,
Rafael