From: Peter Zijlstra <peterz@infradead.org> To: ville.syrjala@linux.intel.com Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Daniel Lezcano <daniel.lezcano@linaro.org>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com> Subject: Re: [PATCH] Revert "cpuidle: Replace ktime_get() with local_clock()" Date: Thu, 20 Apr 2017 15:08:13 +0200 [thread overview] Message-ID: <20170420130813.h7dycr5cptbrvdkz@hirez.programming.kicks-ass.net> (raw) In-Reply-To: <20170420124447.13716-1-ville.syrjala@linux.intel.com> On Thu, Apr 20, 2017 at 03:44:47PM +0300, ville.syrjala@linux.intel.com wrote: > From: Ville Syrjälä <ville.syrjala@linux.intel.com> > > This reverts commit e93e59ce5b85e6c2b444f09fd1f707274ec066dc. > > The TSC stops in deeper C states, On some old hardware (Core2 era and before) only. You've forgotten to mention what hardware you've observed problems with. > so using local_clock() in cpuidle But on said hardware, local_clock() isn't an immediate TSC user. > to track the C state residency seems like a bad idea. With local_clock() > powertop is reporting mostly 0% residency for C states here. Presumably > the core is still spending most of its time in some deep C-state since > the totals typically add up to only 5% or so, so perhaps the governor > isn't getting totally confused by these bogus numbers. But let's go > back to using ktime_get() as that at least works correctly across the > board. Does this cure it? --- drivers/cpuidle/cpuidle.c | 2 ++ kernel/sched/clock.c | 7 +++---- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 548b90be7685..e0d4ad108887 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -219,6 +219,8 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, entered_state = target_state->enter(dev, drv, index); start_critical_timings(); + sched_clock_idle_wakeup_event(0); + time_end = ns_to_ktime(local_clock()); trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu); diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 00a45c45beca..15e848706be4 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -347,6 +347,9 @@ void sched_clock_tick(void) { struct sched_clock_data *scd; + if (timekeeping_suspended) + return; + WARN_ON_ONCE(!irqs_disabled()); /* @@ -378,11 +381,7 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event); */ void sched_clock_idle_wakeup_event(u64 delta_ns) { - if (timekeeping_suspended) - return; - sched_clock_tick(); - touch_softlockup_watchdog_sched(); } EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org> To: ville.syrjala@linux.intel.com Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Daniel Lezcano <daniel.lezcano@linaro.org>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com> Subject: Re: [PATCH] Revert "cpuidle: Replace ktime_get() with local_clock()" Date: Thu, 20 Apr 2017 15:08:13 +0200 [thread overview] Message-ID: <20170420130813.h7dycr5cptbrvdkz@hirez.programming.kicks-ass.net> (raw) In-Reply-To: <20170420124447.13716-1-ville.syrjala@linux.intel.com> On Thu, Apr 20, 2017 at 03:44:47PM +0300, ville.syrjala@linux.intel.com wrote: > From: Ville Syrj�l� <ville.syrjala@linux.intel.com> > > This reverts commit e93e59ce5b85e6c2b444f09fd1f707274ec066dc. > > The TSC stops in deeper C states, On some old hardware (Core2 era and before) only. You've forgotten to mention what hardware you've observed problems with. > so using local_clock() in cpuidle But on said hardware, local_clock() isn't an immediate TSC user. > to track the C state residency seems like a bad idea. With local_clock() > powertop is reporting mostly 0% residency for C states here. Presumably > the core is still spending most of its time in some deep C-state since > the totals typically add up to only 5% or so, so perhaps the governor > isn't getting totally confused by these bogus numbers. But let's go > back to using ktime_get() as that at least works correctly across the > board. Does this cure it? --- drivers/cpuidle/cpuidle.c | 2 ++ kernel/sched/clock.c | 7 +++---- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 548b90be7685..e0d4ad108887 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -219,6 +219,8 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, entered_state = target_state->enter(dev, drv, index); start_critical_timings(); + sched_clock_idle_wakeup_event(0); + time_end = ns_to_ktime(local_clock()); trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu); diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 00a45c45beca..15e848706be4 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -347,6 +347,9 @@ void sched_clock_tick(void) { struct sched_clock_data *scd; + if (timekeeping_suspended) + return; + WARN_ON_ONCE(!irqs_disabled()); /* @@ -378,11 +381,7 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event); */ void sched_clock_idle_wakeup_event(u64 delta_ns) { - if (timekeeping_suspended) - return; - sched_clock_tick(); - touch_softlockup_watchdog_sched(); } EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
next prev parent reply other threads:[~2017-04-20 13:08 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-04-20 12:44 [PATCH] Revert "cpuidle: Replace ktime_get() with local_clock()" ville.syrjala 2017-04-20 13:07 ` Daniel Lezcano 2017-04-20 13:08 ` Peter Zijlstra [this message] 2017-04-20 13:08 ` Peter Zijlstra 2017-04-20 13:43 ` Ville Syrjälä 2017-04-20 13:43 ` Ville Syrjälä 2017-04-20 13:49 ` Peter Zijlstra 2017-04-20 13:49 ` Peter Zijlstra 2017-04-20 14:37 ` Daniel Lezcano 2017-04-20 14:41 ` Peter Zijlstra 2017-04-20 14:47 ` Peter Zijlstra
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