Re: [RFT] [PATCH v2] cpuidle: menu: Skip tick_nohz_get_sleep_length() call in some cases

[Doug Smythies]

On Thu, Aug 10, 2023 at 11:38 AM Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Subject: [PATCH] cpuidle: menu: Skip tick_nohz_get_sleep_length() call in some cases
>
> Because the cost of calling tick_nohz_get_sleep_length() may increase
> in the future, reorder the code in menu_select() so it first uses the
> statistics to determine the expected idle duration.  If that value is
> higher than RESIDENCY_THRESHOLD_NS, tick_nohz_get_sleep_length() will
> be called to obtain the time till the closest timer and refine the
> idle duration prediction if necessary.
>
> This causes the governor to always take the full overhead of
> get_typical_interval() with the assumption that the cost will be
> amortized by skipping the tick_nohz_get_sleep_length() call in the
> cases when the predicted idle duration is relatively very small.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

I ran the same tests as I did for the teo governor changes.
Nothing of significance to report (well, some minor improvements
in records per second at the long interval end of the sleeping
ebizzy test, with a corresponding slight increase in processor
package power).

Tested-by: Doug Smythies <dsmythies@xxxxxxxxx>

> ---
>
> v1 -> v2: Add missing max check to get_typical_interval().
>

... Doug