| Message ID | 2753018.aK9edJ7Dvu@aspire.rjw.lan (mailing list archive) |
|---|---|
| State | Mainlined |
| Delegated to: | Rafael Wysocki |
| Headers | show |
| Series | cpuidle: menu: Fixes, optimizations and cleanups | expand |
On Tue, Oct 02, 2018 at 11:46:28PM +0200, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > If the next timer event (with the tick excluded) is closer than the > target residency of the second state or the PM QoS latency constraint > is below its exit latency, state[0] will be used regardless of any > other factors, so skip the computations in menu_select() then and > return 0 straight away from it. > > Still, do that after the bucket has been determined to avoid > disturbing the wakeup statistics in general. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > drivers/cpuidle/governors/menu.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > Index: linux-pm/drivers/cpuidle/governors/menu.c > =================================================================== > --- linux-pm.orig/drivers/cpuidle/governors/menu.c > +++ linux-pm/drivers/cpuidle/governors/menu.c > @@ -309,6 +309,18 @@ static int menu_select(struct cpuidle_dr > get_iowait_load(&nr_iowaiters, &cpu_load); > data->bucket = which_bucket(data->next_timer_us, nr_iowaiters); > > + if (unlikely(drv->state_count <= 1) || I'm not sure this test is necessary. If state_count == 0, we don't have to select anything as the cpuidle can't register because of: static int __cpuidle_register_driver(struct cpuidle_driver *drv) { int ret; if (!drv || !drv->state_count) return -EINVAL; [ ... ] } If state_count == 1, then there is nothing to select, it is always the state 0. > + ((data->next_timer_us < drv->states[1].target_residency || > + latency_req < drv->states[1].exit_latency) && > + !drv->states[0].disabled && !dev->states_usage[0].disable)) { > + /* > + * In this case state[0] will be used no matter what, so return > + * it right away and keep the tick running. > + */ > + *stop_tick = false; > + return 0; > + } > + > /* > * Force the result of multiplication to be 64 bits even if both > * operands are 32 bits. >
On Thu, Oct 4, 2018 at 5:50 PM Daniel Lezcano <daniel.lezcano@linaro.org> wrote: > > On Tue, Oct 02, 2018 at 11:46:28PM +0200, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > If the next timer event (with the tick excluded) is closer than the > > target residency of the second state or the PM QoS latency constraint > > is below its exit latency, state[0] will be used regardless of any > > other factors, so skip the computations in menu_select() then and > > return 0 straight away from it. > > > > Still, do that after the bucket has been determined to avoid > > disturbing the wakeup statistics in general. > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > --- > > drivers/cpuidle/governors/menu.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > Index: linux-pm/drivers/cpuidle/governors/menu.c > > =================================================================== > > --- linux-pm.orig/drivers/cpuidle/governors/menu.c > > +++ linux-pm/drivers/cpuidle/governors/menu.c > > @@ -309,6 +309,18 @@ static int menu_select(struct cpuidle_dr > > get_iowait_load(&nr_iowaiters, &cpu_load); > > data->bucket = which_bucket(data->next_timer_us, nr_iowaiters); > > > > + if (unlikely(drv->state_count <= 1) || > > I'm not sure this test is necessary. Yes, it is IMO. Strictly speaking it prevents state[1] from being accessed if the count is not 2 at least. > If state_count == 0, we don't have to select anything as the cpuidle can't register because of: > > static int __cpuidle_register_driver(struct cpuidle_driver *drv) > { > int ret; > > if (!drv || !drv->state_count) > return -EINVAL; > > [ ... ] > } > > If state_count == 1, then there is nothing to select, it is always the state 0. Which is why it is better to simply return 0 right away in this case. :-) I guess I could compare state_count just to 1, but <= 1 works too.
Index: linux-pm/drivers/cpuidle/governors/menu.c =================================================================== --- linux-pm.orig/drivers/cpuidle/governors/menu.c +++ linux-pm/drivers/cpuidle/governors/menu.c @@ -309,6 +309,18 @@ static int menu_select(struct cpuidle_dr get_iowait_load(&nr_iowaiters, &cpu_load); data->bucket = which_bucket(data->next_timer_us, nr_iowaiters); + if (unlikely(drv->state_count <= 1) || + ((data->next_timer_us < drv->states[1].target_residency || + latency_req < drv->states[1].exit_latency) && + !drv->states[0].disabled && !dev->states_usage[0].disable)) { + /* + * In this case state[0] will be used no matter what, so return + * it right away and keep the tick running. + */ + *stop_tick = false; + return 0; + } + /* * Force the result of multiplication to be 64 bits even if both * operands are 32 bits.