On Tuesday, October 9, 2018 12:26:48 AM CEST Rafael J. Wysocki wrote:
> On Tue, Oct 9, 2018 at 12:14 AM Doug Smythies <[email protected]> wrote:
> >
> > On 2018.10.08 00:51 Rafael J. Wysocki wrote:
> > > On Mon, Oct 8, 2018 at 8:02 AM Doug Smythies <[email protected]> wrote:
> > >>
> > >> On 2018.10.03 23:56 Rafael J. Wysocki wrote:
> > >>> On Tue, Oct 2, 2018 at 11:51 PM Rafael J. Wysocki <[email protected]>
> > >>> wrote:
>
> [cut]
>
> > >> Test 2: pipe test 2 CPUs, one core. CPU test:
> > >>
> > >> The average loop times graph is here:
> > >> http://fast.smythies.com/linux-pm/k419/k419-rjw-pipe-1core.png
> > >>
> > >> The power and idle statistics graphs are here:
> > >> http://fast.smythies.com/linux-pm/k419/k419-rjw-pipe-1core.htm
> > >>
> > >> Conclusions:
> > >>
> > >> Better performance at the cost of more power with
> > >> the patch set, but late August had both better performance
> > >> and less power.
> > >>
> > >> Overall idle entries and exits are about the same, but way
> > >> way more idle state 0 entries and exits with the patch set.
> > >
> > >Same as above (and expected too).
> >
> > I Disagree. The significant transfer of idle entries from
> > idle state 1 with kernel 4.19-rc6 to idle state 0 with the
> > additional 8 patch set is virtually entirely due to this patch:
> >
> > "[PATCH 2/6] cpuidle: menu: Compute first_idx when latency_req is known"
>
> OK
>
> > As far as I can determine from all of this data, in particular the
> > histogram data below, it seems to me that it now is selecting
> > idle state 0 whereas before it was selecting idle state 1
> > is the correct decision for those very short duration idle states
> > (well, for my processor (older i7-2600K) at least).
>
> At least, that's a matter of consistency IMO.
>
> State 1 should not be selected if the final latency limit is below its
> exit latency and that's what happens in that situation.
>
> > Note: I did test my above assertion with kernels compiled with only
> > the first 2 and then 3 of the 8 patch set.
>
> I see.
While at it, could you test the appended patch (on top of the previous 8)
for me please?
I think that this code can be simplified now.
---
drivers/cpuidle/governors/menu.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
Index: linux-pm/drivers/cpuidle/governors/menu.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/governors/menu.c
+++ linux-pm/drivers/cpuidle/governors/menu.c
@@ -371,12 +371,12 @@ static int menu_select(struct cpuidle_dr
if (s->target_residency > predicted_us) {
/*
* Use a physical idle state, not busy polling, unless
- * a timer is going to trigger really really soon.
+ * a timer is going to trigger soon enough.
*/
if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
- i == idx + 1 && latency_req > s->exit_latency &&
- data->next_timer_us > max_t(unsigned int, 20,
- s->target_residency)) {
+ s->exit_latency <= latency_req &&
+ s->target_residency <= data->next_timer_us) {
+ predicted_us = s->target_residency;
idx = i;
break;
}
