From: Frederic Weisbecker <frederic@kernel.org>
To: Anna-Maria Behnsen <anna-maria@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
John Stultz <john.stultz@linaro.org>,
Eric Dumazet <edumazet@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
linux-pm@vger.kernel.org, Arjan van de Ven <arjan@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Rik van Riel <riel@redhat.com>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH v3 01/17] cpufreq: Prepare timer flags for hierarchical timer pull model
Date: Wed, 26 Oct 2022 15:54:23 +0200 [thread overview]
Message-ID: <20221026135423.GA1329996@lothringen> (raw)
In-Reply-To: <20221025135850.51044-2-anna-maria@linutronix.de>
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
>
next prev parent reply other threads:[~2022-10-26 13:56 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-25 13:58 [PATCH v3 00/17] timer: Move from a push remote at enqueue to a pull at expiry model Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 01/17] cpufreq: Prepare timer flags for hierarchical timer pull model Anna-Maria Behnsen
2022-10-26 13:54 ` Frederic Weisbecker [this message]
2022-10-31 15:22 ` Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 02/17] tick-sched: Warn when next tick seems to be in the past Anna-Maria Behnsen
2022-10-25 22:11 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 03/17] timer: Move store of next event into __next_timer_interrupt() Anna-Maria Behnsen
2022-10-26 9:33 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 04/17] timer: Split next timer interrupt logic Anna-Maria Behnsen
2022-10-26 9:40 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 05/17] timer: Rework idle logic Anna-Maria Behnsen
2022-10-26 13:27 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 06/17] timer: Keep the pinned timers separate from the others Anna-Maria Behnsen
2022-10-26 15:26 ` Frederic Weisbecker
2022-10-25 13:58 ` [PATCH v3 07/17] timer: Retrieve next expiry of pinned/non-pinned timers seperately Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 08/17] timer: Rename get_next_timer_interrupt() Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 09/17] timer: Split out "get next timer interrupt" functionality Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 10/17] timer: Add get next timer interrupt functionality for remote CPUs Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 11/17] timer: Restructure internal locking Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 12/17] timer: Check if timers base is handled already Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 13/17] tick/sched: Split out jiffies update helper function Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 14/17] timer: Implement the hierarchical pull model Anna-Maria Behnsen
2022-10-25 16:36 ` kernel test robot
2022-10-26 5:35 ` kernel test robot
2022-10-27 7:38 ` kernel test robot
2022-10-25 13:58 ` [PATCH v3 15/17] timer_migration: Add tracepoints Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 16/17] add_timer_on(): Make sure callers have TIMER_PINNED flag Anna-Maria Behnsen
2022-10-25 13:58 ` [PATCH v3 17/17] timer: Always queue timers on the local CPU Anna-Maria Behnsen
2022-10-27 7:22 ` kernel test robot
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