| Message ID | 1561295.epLgDtImU0@aspire.rjw.lan (mailing list archive) |
|---|---|
| State | Mainlined |
| Delegated to: | Rafael Wysocki |
| Headers | show |
| Series | cpuidle: menu: Fixes, optimizations and cleanups | expand |
On 02/10/2018 23:42, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > If the CPU exits the "polling" state due to the time limit in the > loop in poll_idle(), this is not a real wakeup and it just means > that the "polling" state selection was not adequate. The governor > mispredicted short idle duration, but had a more suitable state been > selected, the CPU might have spent more time in it. In fact, there > is no reason to expect that there would have been a wakeup event > earlier than the next timer in that case. > > Handling such cases as regular wakeups in menu_update() may cause the > menu governor to make suboptimal decisions going forward, but ignoring > them altogether would not be correct either, because every time > menu_select() is invoked, it makes a separate new attempt to predict > the idle duration taking distinct time to the closest timer event as > input and the outcomes of all those attempts should be recorded. > > For this reason, make menu_update() always assume that if the > "polling" state was exited due to the time limit, the next proper > wakeup event for the CPU would be the next timer event (not > including the tick). > > Fixes: a37b969a61c1 "cpuidle: poll_state: Add time limit to poll_idle()" > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org> > drivers/cpuidle/governors/menu.c | 10 ++++++++++ > drivers/cpuidle/poll_state.c | 6 +++++- > include/linux/cpuidle.h | 1 + > 3 files changed, 16 insertions(+), 1 deletion(-) > > Index: linux-pm/drivers/cpuidle/governors/menu.c > =================================================================== > --- linux-pm.orig/drivers/cpuidle/governors/menu.c > +++ linux-pm/drivers/cpuidle/governors/menu.c > @@ -511,6 +511,16 @@ static void menu_update(struct cpuidle_d > * duration predictor do a better job next time. > */ > measured_us = 9 * MAX_INTERESTING / 10; > + } else if ((drv->states[last_idx].flags & CPUIDLE_FLAG_POLLING) && > + dev->poll_time_limit) { > + /* > + * The CPU exited the "polling" state due to a time limit, so > + * the idle duration prediction leading to the selection of that > + * state was inaccurate. If a better prediction had been made, > + * the CPU might have been woken up from idle by the next timer. > + * Assume that to be the case. > + */ > + measured_us = data->next_timer_us; > } else { > /* measured value */ > measured_us = dev->last_residency; > Index: linux-pm/include/linux/cpuidle.h > =================================================================== > --- linux-pm.orig/include/linux/cpuidle.h > +++ linux-pm/include/linux/cpuidle.h > @@ -81,6 +81,7 @@ struct cpuidle_device { > unsigned int registered:1; > unsigned int enabled:1; > unsigned int use_deepest_state:1; > + unsigned int poll_time_limit:1; > unsigned int cpu; > > int last_residency; > Index: linux-pm/drivers/cpuidle/poll_state.c > =================================================================== > --- linux-pm.orig/drivers/cpuidle/poll_state.c > +++ linux-pm/drivers/cpuidle/poll_state.c > @@ -17,6 +17,8 @@ static int __cpuidle poll_idle(struct cp > { > u64 time_start = local_clock(); > > + dev->poll_time_limit = false; > + > local_irq_enable(); > if (!current_set_polling_and_test()) { > unsigned int loop_count = 0; > @@ -27,8 +29,10 @@ static int __cpuidle poll_idle(struct cp > continue; > > loop_count = 0; > - if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT) > + if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT) { > + dev->poll_time_limit = true; > break; > + } > } > } > current_clr_polling(); >
Index: linux-pm/drivers/cpuidle/governors/menu.c =================================================================== --- linux-pm.orig/drivers/cpuidle/governors/menu.c +++ linux-pm/drivers/cpuidle/governors/menu.c @@ -511,6 +511,16 @@ static void menu_update(struct cpuidle_d * duration predictor do a better job next time. */ measured_us = 9 * MAX_INTERESTING / 10; + } else if ((drv->states[last_idx].flags & CPUIDLE_FLAG_POLLING) && + dev->poll_time_limit) { + /* + * The CPU exited the "polling" state due to a time limit, so + * the idle duration prediction leading to the selection of that + * state was inaccurate. If a better prediction had been made, + * the CPU might have been woken up from idle by the next timer. + * Assume that to be the case. + */ + measured_us = data->next_timer_us; } else { /* measured value */ measured_us = dev->last_residency; Index: linux-pm/include/linux/cpuidle.h =================================================================== --- linux-pm.orig/include/linux/cpuidle.h +++ linux-pm/include/linux/cpuidle.h @@ -81,6 +81,7 @@ struct cpuidle_device { unsigned int registered:1; unsigned int enabled:1; unsigned int use_deepest_state:1; + unsigned int poll_time_limit:1; unsigned int cpu; int last_residency; Index: linux-pm/drivers/cpuidle/poll_state.c =================================================================== --- linux-pm.orig/drivers/cpuidle/poll_state.c +++ linux-pm/drivers/cpuidle/poll_state.c @@ -17,6 +17,8 @@ static int __cpuidle poll_idle(struct cp { u64 time_start = local_clock(); + dev->poll_time_limit = false; + local_irq_enable(); if (!current_set_polling_and_test()) { unsigned int loop_count = 0; @@ -27,8 +29,10 @@ static int __cpuidle poll_idle(struct cp continue; loop_count = 0; - if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT) + if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT) { + dev->poll_time_limit = true; break; + } } } current_clr_polling();