From: Anna-Maria Behnsen <anna-maria@linutronix.de>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
John Stultz <jstultz@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Eric Dumazet <edumazet@google.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Arjan van de Ven <arjan@infradead.org>,
"Paul E . McKenney" <paulmck@kernel.org>,
Rik van Riel <riel@surriel.com>,
Steven Rostedt <rostedt@goodmis.org>,
Sebastian Siewior <bigeasy@linutronix.de>,
Giovanni Gherdovich <ggherdovich@suse.cz>,
Lukasz Luba <lukasz.luba@arm.com>,
"Gautham R . Shenoy" <gautham.shenoy@amd.com>,
Srinivas Pandruvada <srinivas.pandruvada@intel.com>,
K Prateek Nayak <kprateek.nayak@amd.com>
Subject: Re: [PATCH v10 04/20] timers: Optimization for timer_base_try_to_set_idle()
Date: Mon, 22 Jan 2024 12:48:21 +0100 [thread overview]
Message-ID: <87r0i9y4fu.fsf@somnus> (raw)
In-Reply-To: <ZagEK9l06c_7F3pH@localhost.localdomain>
Frederic Weisbecker <frederic@kernel.org> writes:
> Le Mon, Jan 15, 2024 at 03:37:27PM +0100, Anna-Maria Behnsen a écrit :
>> When tick is stopped also the timer base is_idle flag is set. When
>> reentering the timer_base_try_to_set_idle() with the tick stopped, there is
>> no need to check whether the timer base needs to be set idle again. When a
>> timer was enqueued in the meantime, this is already handled by the
>> tick_nohz_next_event() call which was executed before
>> tick_nohz_stop_tick().
>>
>> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
>> ---
>> kernel/time/tick-sched.c | 2 +-
>> kernel/time/timer.c | 11 ++++++++---
>> 2 files changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
>> index c6223afc801f..27f1a2ae7f39 100644
>> --- a/kernel/time/tick-sched.c
>> +++ b/kernel/time/tick-sched.c
>> @@ -886,7 +886,7 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
>> struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
>> unsigned long basejiff = ts->last_jiffies;
>> u64 basemono = ts->timer_expires_base;
>> - bool timer_idle;
>> + bool timer_idle = ts->tick_stopped;
>> u64 expires;
>>
>> /* Make sure we won't be trying to stop it twice in a row. */
>> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
>> index 3a668060692e..2f69a485a070 100644
>> --- a/kernel/time/timer.c
>> +++ b/kernel/time/timer.c
>> @@ -1999,13 +1999,18 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
>> * timer_base_try_to_set_idle() - Try to set the idle state of the timer bases
>> * @basej: base time jiffies
>> * @basem: base time clock monotonic
>> - * @idle: pointer to store the value of timer_base->is_idle
>> + * @idle: pointer to store the value of timer_base->is_idle on return;
>> + * *idle contains the information whether tick was already stopped
>> *
>> - * Returns the tick aligned clock monotonic time of the next pending
>> - * timer or KTIME_MAX if no timer is pending.
>> + * Returns the tick aligned clock monotonic time of the next pending timer or
>> + * KTIME_MAX if no timer is pending. When tick was already stopped KTIME_MAX is
>> + * returned as well.
>> */
>> u64 timer_base_try_to_set_idle(unsigned long basej, u64 basem, bool *idle)
>> {
>> + if (*idle)
>> + return KTIME_MAX;
>
> Ok now I see the reason behind the behavioural change.
>
> So either:
>
> * We remove the old behaviour consisting in clearing base->is_idle if the new
> next timer is within a jiffy while the tick is stopped. But then the changelog
> from the previous patch should state that and comments must be clarified.
>
I would like to take 'either'. I thought the changelog already mentioned
it. But maybe I have to make it more explicit. I'll go and rework the
comments once more.
Thanks,
Anna-Maria
next prev parent reply other threads:[~2024-01-22 11:48 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-15 14:37 [PATCH v10 00/20] timers: Move from a push remote at enqueue to a pull at expiry model Anna-Maria Behnsen
2024-01-15 14:37 ` [PATCH v10 01/20] timers: Restructure get_next_timer_interrupt() Anna-Maria Behnsen
2024-01-17 15:01 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 02/20] timers: Split out get next timer interrupt Anna-Maria Behnsen
2024-01-17 15:06 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 03/20] timers: Move marking timer bases idle into tick_nohz_stop_tick() Anna-Maria Behnsen
2024-01-17 16:02 ` Frederic Weisbecker
2024-01-22 11:45 ` Anna-Maria Behnsen
2024-01-22 21:49 ` Frederic Weisbecker
2024-02-19 8:52 ` [PATCH v10a] " Anna-Maria Behnsen
2024-02-19 22:37 ` Frederic Weisbecker
2024-02-20 10:48 ` Anna-Maria Behnsen
2024-02-20 11:41 ` Frederic Weisbecker
2024-02-20 12:02 ` Anna-Maria Behnsen
2024-02-20 12:34 ` Frederic Weisbecker
2024-02-20 14:00 ` Anna-Maria Behnsen
2024-02-20 15:10 ` Frederic Weisbecker
2024-02-20 15:23 ` Anna-Maria Behnsen
2024-02-20 15:25 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 04/20] timers: Optimization for timer_base_try_to_set_idle() Anna-Maria Behnsen
2024-01-17 16:45 ` Frederic Weisbecker
2024-01-22 11:48 ` Anna-Maria Behnsen [this message]
2024-01-22 22:22 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 05/20] timers: Introduce add_timer() variants which modify timer flags Anna-Maria Behnsen
2024-01-17 17:01 ` Frederic Weisbecker
2024-01-22 11:50 ` Anna-Maria Behnsen
2024-01-15 14:37 ` [PATCH v10 06/20] workqueue: Use global variant for add_timer() Anna-Maria Behnsen
2024-01-15 14:37 ` [PATCH v10 07/20] timers: add_timer_on(): Make sure TIMER_PINNED flag is set Anna-Maria Behnsen
2024-01-15 14:37 ` [PATCH v10 08/20] timers: Ease code in run_local_timers() Anna-Maria Behnsen
2024-01-15 14:37 ` [PATCH v10 09/20] timers: Split next timer interrupt logic Anna-Maria Behnsen
2024-01-23 14:28 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 10/20] timers: Keep the pinned timers separate from the others Anna-Maria Behnsen
2024-01-15 14:37 ` [PATCH v10 11/20] timers: Retrieve next expiry of pinned/non-pinned timers separately Anna-Maria Behnsen
2024-01-15 14:37 ` [PATCH v10 12/20] timers: Split out "get next timer interrupt" functionality Anna-Maria Behnsen
2024-01-15 14:37 ` [PATCH v10 13/20] timers: Add get next timer interrupt functionality for remote CPUs Anna-Maria Behnsen
2024-02-19 16:04 ` Frederic Weisbecker
2024-02-19 16:57 ` Anna-Maria Behnsen
2024-01-15 14:37 ` [PATCH v10 14/20] timers: Restructure internal locking Anna-Maria Behnsen
2024-01-24 13:56 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 15/20] timers: Check if timers base is handled already Anna-Maria Behnsen
2024-01-24 14:22 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 16/20] tick/sched: Split out jiffies update helper function Anna-Maria Behnsen
2024-01-24 14:42 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 17/20] timers: Introduce function to check timer base is_idle flag Anna-Maria Behnsen
2024-01-24 14:52 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 18/20] timers: Implement the hierarchical pull model Anna-Maria Behnsen
2024-01-25 14:30 ` Frederic Weisbecker
2024-01-28 15:58 ` Anna-Maria Behnsen
2024-01-30 15:29 ` Frederic Weisbecker
2024-01-30 16:45 ` Anna-Maria Behnsen
2024-01-26 12:53 ` Frederic Weisbecker
2024-01-27 22:54 ` Frederic Weisbecker
2024-01-29 10:50 ` Anna-Maria Behnsen
2024-01-29 22:21 ` Frederic Weisbecker
2024-01-30 13:32 ` Anna-Maria Behnsen
2024-01-29 13:50 ` Paul E. McKenney
2024-01-29 1:04 ` Frederic Weisbecker
2024-01-30 17:56 ` Anna-Maria Behnsen
2024-01-30 21:13 ` Frederic Weisbecker
2024-01-31 11:19 ` Anna-Maria Behnsen
2024-01-30 15:37 ` Frederic Weisbecker
2024-02-01 14:59 ` Anna-Maria Behnsen
2024-02-01 15:05 ` Frederic Weisbecker
2024-02-01 16:15 ` Anna-Maria Behnsen
2024-02-01 17:43 ` Frederic Weisbecker
2024-02-01 20:52 ` Anna-Maria Behnsen
2024-02-05 13:29 ` Anna-Maria Behnsen
2024-02-05 20:30 ` Frederic Weisbecker
2024-02-06 10:06 ` Anna-Maria Behnsen
2024-02-06 10:29 ` Frederic Weisbecker
2024-02-01 16:33 ` Frederic Weisbecker
2024-02-05 15:59 ` Anna-Maria Behnsen
2024-02-05 20:28 ` Frederic Weisbecker
2024-02-04 22:02 ` Frederic Weisbecker
2024-02-06 11:03 ` Anna-Maria Behnsen
2024-02-06 11:11 ` Frederic Weisbecker
2024-02-04 22:32 ` Frederic Weisbecker
2024-02-06 11:36 ` Anna-Maria Behnsen
2024-02-06 13:21 ` Frederic Weisbecker
2024-02-06 14:13 ` Anna-Maria Behnsen
2024-02-06 14:21 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 19/20] timer_migration: Add tracepoints Anna-Maria Behnsen
2024-02-01 16:47 ` Frederic Weisbecker
2024-01-15 14:37 ` [PATCH v10 20/20] timers: Always queue timers on the local CPU Anna-Maria Behnsen
2024-02-01 17:36 ` Frederic Weisbecker
2024-02-01 20:58 ` Anna-Maria Behnsen
2024-02-02 11:57 ` Frederic Weisbecker
2024-01-30 22:07 ` [PATCH v10 00/20] timers: Move from a push remote at enqueue to a pull at expiry model Christian Loehle
2024-02-01 15:03 ` Anna-Maria Behnsen
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