Re: [PATCH 3/6] cpuidle: menu: Get rid of first_idx from menu_select()

Peter Zijlstra
2018-10-04T08:00:06Z

On Thu, Oct 04, 2018 at 09:53:39AM +0200, Rafael J. Wysocki wrote:
> On Thu, Oct 4, 2018 at 9:46 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Tue, Oct 02, 2018 at 11:44:06PM +0200, Rafael J. Wysocki wrote:
> > > idx = -1;
> > > - for (i = first_idx; i < drv->state_count; i++) {
> > > + for (i = 0; i < drv->state_count; i++) {
> > > struct cpuidle_state *s = &drv->states[i];
> > > struct cpuidle_state_usage *su = &dev->states_usage[i];
> > >
> > > if (s->disabled || su->disable)
> > > continue;
> > > +
> > > if (idx == -1)
> > > idx = i; /* first enabled state */
> > > +
> > > if (s->target_residency > predicted_us) {
> > > + /*
> > > + * Use a physical idle state, not busy polling, unless
> > > + * a timer is going to trigger really really soon.
> > > + */
> > > + 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)) {
> >
> > Not new in this patch, but this is where I really noticed it; that 20,
> > should that not be something like: POLL_IDLE_TIME_LIMIT / NSEC_PER_USEC
> > ?
>
> The POLL_IDLE_TIME_LIMIT is how much time we allow it to spin in
> idle_poll() and I'm not sure it is related. Besides, I want it to go
> away actually (https://patchwork.kernel.org/patch/10624117/).

Ah, ok. Making it go away is better still!