diff mbox series

[RFC,3/3] cpuidle,teo: Improve state selection

Message ID 20230728145808.970594909@infradead.org
State New
Headers
Series cpuidle,teo: Improve TEO tick decisions |

Commit Message

Peter Zijlstra July 28, 2023, 2:55 p.m. UTC 
  When selecting a state, stop when history tells us 66% of recent idles
were at or below our current state.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 drivers/cpuidle/governors/teo.c |    6 ++++++
 1 file changed, 6 insertions(+)

Comments

Rafael J. Wysocki July 28, 2023, 5:07 p.m. UTC | #1 
On Fri, Jul 28, 2023 at 5:01 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> When selecting a state, stop when history tells us 66% of recent idles
> were at or below our current state.

This is not really about "recent idles" AFAICS.  It stops the
selection when 66% of the total sum of the "hits" and "intercepts"
signals comes from the current state and the states below it.  This
covers the entire history, while the "recent" ones are counted
separately.

> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>  drivers/cpuidle/governors/teo.c |    6 ++++++
>  1 file changed, 6 insertions(+)
>
> --- a/drivers/cpuidle/governors/teo.c
> +++ b/drivers/cpuidle/governors/teo.c
> @@ -363,6 +363,7 @@ static int teo_select(struct cpuidle_dri
>         unsigned int idx_hit_sum = 0;
>         unsigned int hit_sum = 0;
>         unsigned int tick_sum = 0;
> +       unsigned int thresh_sum = 0;
>         int constraint_idx = 0;
>         int idx0 = 0, idx = -1;
>         bool alt_intercepts, alt_recent;
> @@ -397,6 +398,8 @@ static int teo_select(struct cpuidle_dri
>                 duration_ns = tick_nohz_get_sleep_length(&delta_tick);
>         cpu_data->sleep_length_ns = duration_ns;
>
> +       thresh_sum = 2 * cpu_data->total / 3; /* 66% */
> +
>         /*
>          * Find the deepest idle state whose target residency does not exceed
>          * the current sleep length and the deepest idle state not deeper than
> @@ -427,6 +430,9 @@ static int teo_select(struct cpuidle_dri
>                 if (s->target_residency_ns > duration_ns)
>                         break;
>
> +               if (intercept_sum + hit_sum > thresh_sum)
> +                       break;
> +
>                 idx = i;
>
>                 if (s->exit_latency_ns <= latency_req)
>
>
Peter Zijlstra July 29, 2023, 8:46 a.m. UTC | #2 
On Fri, Jul 28, 2023 at 07:07:02PM +0200, Rafael J. Wysocki wrote:
> On Fri, Jul 28, 2023 at 5:01 PM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > When selecting a state, stop when history tells us 66% of recent idles
> > were at or below our current state.
> 
> This is not really about "recent idles" AFAICS.  It stops the
> selection when 66% of the total sum of the "hits" and "intercepts"
> signals comes from the current state and the states below it.  This
> covers the entire history, while the "recent" ones are counted
> separately.

Ah, bad wording perhaps. I found that 'recent' list teo has very hard to
use, also the regular state isn't that long lived as per the reply on
the previous patch.
diff mbox series

Patch

--- a/drivers/cpuidle/governors/teo.c
+++ b/drivers/cpuidle/governors/teo.c
@@ -363,6 +363,7 @@  static int teo_select(struct cpuidle_dri
 	unsigned int idx_hit_sum = 0;
 	unsigned int hit_sum = 0;
 	unsigned int tick_sum = 0;
+	unsigned int thresh_sum = 0;
 	int constraint_idx = 0;
 	int idx0 = 0, idx = -1;
 	bool alt_intercepts, alt_recent;
@@ -397,6 +398,8 @@  static int teo_select(struct cpuidle_dri
 		duration_ns = tick_nohz_get_sleep_length(&delta_tick);
 	cpu_data->sleep_length_ns = duration_ns;
 
+	thresh_sum = 2 * cpu_data->total / 3; /* 66% */
+
 	/*
 	 * Find the deepest idle state whose target residency does not exceed
 	 * the current sleep length and the deepest idle state not deeper than
@@ -427,6 +430,9 @@  static int teo_select(struct cpuidle_dri
 		if (s->target_residency_ns > duration_ns)
 			break;
 
+		if (intercept_sum + hit_sum > thresh_sum)
+			break;
+
 		idx = i;
 
 		if (s->exit_latency_ns <= latency_req)