Messages in this thread | | | Date | Wed, 26 Oct 2022 15:54:23 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH v3 01/17] cpufreq: Prepare timer flags for hierarchical timer pull model |
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On Tue, Oct 25, 2022 at 03:58:34PM +0200, Anna-Maria Behnsen wrote: > Note: This is a proposal only. I was waiting on input how to change this > driver properly to use the already existing infrastructure. See therfore > the thread on linux-pm mailinglist: > https://lore.kernel.org/linux-pm/4c99f34b-40f1-e6cc-2669-7854b615b5fd@linutronix.de/ > > gpstates timer is the only timer using TIMER_PINNED and TIMER_DEFERRABLE > flag. When moving to hierarchical timer pull model, pinned and deferrable > timers are stored in separate bases. > > To ensure gpstates timer always expires on the CPU where it is pinned to, > keep only TIMER_PINNED flag and drop TIMER_DEFERRABLE flag.
OTOH there are deferrable timers out there that expect to run on a specific CPU, because there are always queued with add_timer_on().
For example workqueues using DECLARE_DEFERRABLE_WORK() that are queued with queue_delayed_work_on(). Like vmstat().
Those are not explicitely pinned because they don't rely on __mod_timer() but they expect CPU affinity.
Thanks.
> > While at it, rewrite comment explaining the rule for timer expiry for the > next interval and fix whitespace damages. > > Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de> > Cc: linux-pm@vger.kernel.org > Cc: Rafael J. Wysocki <rafael@kernel.org> > Cc: Viresh Kumar <viresh.kumar@linaro.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > --- > drivers/cpufreq/powernv-cpufreq.c | 15 +++++++-------- > 1 file changed, 7 insertions(+), 8 deletions(-) > > diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c > index fddbd1ea1635..08d6bd54539d 100644 > --- a/drivers/cpufreq/powernv-cpufreq.c > +++ b/drivers/cpufreq/powernv-cpufreq.c > @@ -640,18 +640,18 @@ static inline int calc_global_pstate(unsigned int elapsed_time, > return highest_lpstate_idx + index_diff; > } > > -static inline void queue_gpstate_timer(struct global_pstate_info *gpstates) > +static inline void queue_gpstate_timer(struct global_pstate_info *gpstates) > { > unsigned int timer_interval; > > /* > - * Setting up timer to fire after GPSTATE_TIMER_INTERVAL ms, But > - * if it exceeds MAX_RAMP_DOWN_TIME ms for ramp down time. > - * Set timer such that it fires exactly at MAX_RAMP_DOWN_TIME > - * seconds of ramp down time. > + * Timer should expire next time after GPSTATE_TIMER_INTERVAL. If > + * the resulting interval (elapsed time + interval) between last > + * and next timer expiry is greater than MAX_RAMP_DOWN_TIME, ensure > + * it is maximum MAX_RAMP_DOWN_TIME when queueing the next timer. > */ > if ((gpstates->elapsed_time + GPSTATE_TIMER_INTERVAL) > - > MAX_RAMP_DOWN_TIME) > + > MAX_RAMP_DOWN_TIME) > timer_interval = MAX_RAMP_DOWN_TIME - gpstates->elapsed_time; > else > timer_interval = GPSTATE_TIMER_INTERVAL; > @@ -865,8 +865,7 @@ static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy) > > /* initialize timer */ > gpstates->policy = policy; > - timer_setup(&gpstates->timer, gpstate_timer_handler, > - TIMER_PINNED | TIMER_DEFERRABLE); > + timer_setup(&gpstates->timer, gpstate_timer_handler, TIMER_PINNED); > gpstates->timer.expires = jiffies + > msecs_to_jiffies(GPSTATE_TIMER_INTERVAL); > spin_lock_init(&gpstates->gpstate_lock); > -- > 2.30.2 >
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