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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