| Message ID | 20190226145415.19411-8-ulf.hansson@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | PM / Domains: Support hierarchical CPU arrangement (PSCI/ARM) | expand |
On Tue, Feb 26, 2019 at 11:08 PM Rafael J. Wysocki <rafael@kernel.org> wrote: > > On Tue, Feb 26, 2019 at 3:54 PM Ulf Hansson <ulf.hansson@linaro.org> wrote: > > > > A common piece of data used by cpuidle governors, is the information about > > when the next timer/tick is going to fire. Rather than having each governor > > calling tick_nohz_get_next_timer|hrtimer() separately, let's consolidate > > the code by calling these functions before invoking the ->select() callback > > of the governor - and store the output data in the struct cpuidle_device. > > That misses the point IMO. > > You don't need to store two values in struct cpuidle_device, but just > one, and not before running ->select(), but before invoking the > driver's ->enter() callback. > > At that point, the decision on whether or not to stop the scheduler > tick has been made already and it should be sufficient to store the > return value of tick_nohz_get_next_hrtimer() introduced by patch > [3/8], Or the difference between in and ts->idle_entrytime for that matter, whichever is more useful. > because that value represents the next timer regardless of what > has been decided with respect to the tick. > > And you won't need the tick_nohz_get_next_timer() any more then.
On Wed, 27 Feb 2019 at 00:41, Rafael J. Wysocki <rafael@kernel.org> wrote: > > On Wed, Feb 27, 2019 at 12:16 AM Ulf Hansson <ulf.hansson@linaro.org> wrote: > > > > On Tue, 26 Feb 2019 at 23:08, Rafael J. Wysocki <rafael@kernel.org> wrote: > > > > > > On Tue, Feb 26, 2019 at 3:54 PM Ulf Hansson <ulf.hansson@linaro.org> wrote: > > > > > > > > A common piece of data used by cpuidle governors, is the information about > > > > when the next timer/tick is going to fire. Rather than having each governor > > > > calling tick_nohz_get_next_timer|hrtimer() separately, let's consolidate > > > > the code by calling these functions before invoking the ->select() callback > > > > of the governor - and store the output data in the struct cpuidle_device. > > > > > > That misses the point IMO. > > > > > > You don't need to store two values in struct cpuidle_device, but just > > > one, and not before running ->select(), but before invoking the > > > driver's ->enter() callback. > > > > Okay! Thanks for letting me know! > > > > > > > > At that point, the decision on whether or not to stop the scheduler > > > tick has been made already and it should be sufficient to store the > > > return value of tick_nohz_get_next_hrtimer() introduced by patch > > > [3/8], because that value represents the next timer regardless of what > > > has been decided with respect to the tick. > > > > Just to make sure I get this correctly, because it seems like I have > > missed a few points here.... > > > > If we decided to keep the tick running, then > > tick_nohz_get_next_hrtimer() gives the next tick or the next hrtimer, > > whatever that comes first. There are no other timer that can expire > > earlier than this, right!? > > > > If we decided to stop the tick, then tick_nohz_get_next_hrtimer() will > > give us the next hrtimer. Again, then there are no other timer that > > can't expire earlier than this, right!? > > Right in both cases. > > IOW, that is the event that will wake up the CPU unless any other > (non-timer) interrupts (or equivalent events) occur in the meantime. > > > > > > > And you won't need the tick_nohz_get_next_timer() any more then. > > > > Alright, this kind of brings this hole thing back closer to v10 - and > > then we should stick to use tick_nohz_get_sleep_length() as is for the > > cpuidle governors. That is what you are saying? > > For the menu and teo governors - yes. IMO > tick_nohz_get_sleep_length() is as good as it gets in there. Okay, got it! Thanks for your helpful answers! I will post a v12 as soon as I can, so we can look into the other parts of the series. Kind regards Uffe
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 7f108309e871..3b148253036b 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -312,6 +312,8 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, bool *stop_tick) { + dev->next_timer = tick_nohz_get_next_timer(); + dev->next_hrtimer = tick_nohz_get_next_hrtimer(); return cpuidle_curr_governor->select(drv, dev, stop_tick); } diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 95e9122d6047..cdbe434e783d 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -287,8 +287,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, unsigned long nr_iowaiters; ktime_t delta_next; ktime_t now = ktime_get(); - ktime_t next_hrtimer = tick_nohz_get_next_hrtimer(); - ktime_t next_timer = tick_nohz_get_next_timer(); if (data->needs_update) { menu_update(drv, dev); @@ -298,14 +296,14 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, /* * Compute the duration before the next timer, whatever the origin */ - delta_next = ktime_sub(next_timer, now); + delta_next = ktime_sub(dev->next_timer, now); data->next_timer_us = ktime_to_us(delta_next); /* * Compute the duration before next hrtimer which is the tick * or an earliest hrtimer */ - delta_next = ktime_sub(next_hrtimer, now); + delta_next = ktime_sub(dev->next_hrtimer, now); nr_iowaiters = nr_iowait_cpu(dev->cpu); data->bucket = which_bucket(data->next_timer_us, nr_iowaiters); diff --git a/drivers/cpuidle/governors/teo.c b/drivers/cpuidle/governors/teo.c index bef1e95c597e..7af9851d9d40 100644 --- a/drivers/cpuidle/governors/teo.c +++ b/drivers/cpuidle/governors/teo.c @@ -245,8 +245,6 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, int max_early_idx, idx, i; ktime_t delta_tick; ktime_t now = ktime_get(); - ktime_t next_hrtimer = tick_nohz_get_next_hrtimer(); - ktime_t next_timer = tick_nohz_get_next_timer(); if (cpu_data->last_state >= 0) { teo_update(drv, dev); @@ -255,8 +253,8 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, cpu_data->time_span_ns = local_clock(); - cpu_data->sleep_length_ns = ktime_sub(next_timer, now); - delta_tick = ktime_sub(next_hrtimer, now); + cpu_data->sleep_length_ns = ktime_sub(dev->next_timer, now); + delta_tick = ktime_sub(dev->next_hrtimer, now); duration_us = ktime_to_us(cpu_data->sleep_length_ns); count = 0; diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h index 3b39472324a3..81ec924206f0 100644 --- a/include/linux/cpuidle.h +++ b/include/linux/cpuidle.h @@ -83,6 +83,8 @@ struct cpuidle_device { unsigned int use_deepest_state:1; unsigned int poll_time_limit:1; unsigned int cpu; + ktime_t next_timer; + ktime_t next_hrtimer; int last_residency; struct cpuidle_state_usage states_usage[CPUIDLE_STATE_MAX];
A common piece of data used by cpuidle governors, is the information about when the next timer/tick is going to fire. Rather than having each governor calling tick_nohz_get_next_timer|hrtimer() separately, let's consolidate the code by calling these functions before invoking the ->select() callback of the governor - and store the output data in the struct cpuidle_device. Besides the consolidation benefit, the purpose of this change is also to make the information about the next timer/tick, available outside the cpuidle framework. Following changes that implements a new genpd governor, makes use of this. Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> --- Changes in v11: - New patch. --- drivers/cpuidle/cpuidle.c | 2 ++ drivers/cpuidle/governors/menu.c | 6 ++---- drivers/cpuidle/governors/teo.c | 6 ++---- include/linux/cpuidle.h | 2 ++ 4 files changed, 8 insertions(+), 8 deletions(-) -- 2.17.1