Hi Wei,
I'll give it a try and make some measurements. It will probable be a week before I can give any feed back. Its good to see others are looking at this.
Thanks,
Richard W.
> I also found current cpuidle Menu governor should have some problems
> while predicting next non-expected break-event after some expected
> break-events. The measured_us/elapsed_us/predicted_us will become
> larger
> and larger once (measured_us + BREAK_FUZZ >= data->expected_us -
> target->exit_latency). The major point is that it should be
> last_residency, not measured_us, that need to be used to do comparing
> and distinguish between expected & non-expected events.
>
> Below is my draft patch (not tested) for this. It is simple and should
> also be effective for high interrupt rates case.
>
> Jimmy
>
> Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>
>
> diff --git a/drivers/cpuidle/governors/menu.c
> b/drivers/cpuidle/governors/menu.c
> index 78d77c5..dea5250 100644
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -80,18 +80,19 @@ static void menu_reflect(struct cpuidle_device
> *dev)
> if (!(target->flags & CPUIDLE_FLAG_TIME_VALID))
> measured_us = USEC_PER_SEC / HZ;
>
> + /* if wrapping, set to max uint (-1) */
> + measured_us = (data->elapsed_us < measured_us) ? measured_us :
> -1;
> +
> /* Predict time remaining until next break event */
> - if (measured_us + BREAK_FUZZ < data->expected_us -
> target->exit_latency) {
> - data->predicted_us = max(measured_us,
> data->last_measured_us);
> + data->predicted_us = max(measured_us, data->last_measured_us);
> +
> + /* Distinguish between expected & non-expected events */
> + if (cpuidle_get_last_residency(dev) + BREAK_FUZZ
> + < data->expected_us - target->exit_latency) {
> data->last_measured_us = measured_us;
> data->elapsed_us = 0;
> - } else {
> - if (data->elapsed_us < data->elapsed_us + measured_us)
> - data->elapsed_us = measured_us;
> - else
> - data->elapsed_us = -1;
> - data->predicted_us = max(measured_us,
> data->last_measured_us);
> - }
> + } else
> + data->elapsed_us = measured_us;
> }
>
> /**
>
>
> On Tuesday, July 15, 2008 5:02 AM, Woodruff, Richard wrote:
> > Hi,
> >
> > Any comments on the following?
> >
> > I'm finding with high interrupt rates for some USB devices the menu
> governor
> > guesses wrong enough that throughput drops.
> >
> > With the below tweak tests with fixed data sizes which were taking
> 12s
> to
> > complete drop back to 9s. Also my standby idle doesn't change
> before
> and
> > after activity with our with out the patch.
> >
> > What it does is simply timestamp incoming irqs, then in the menu
> governor
> > will use current & last irq time delta to refine its guess as to how
> long
> > sleep will happen.
> >
> > Regards,
> > Richard W.
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