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 <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>,
Frederic Weisbecker <fweisbec@gmail.com>,
Rik van Riel <riel@surriel.com>
Subject: Re: [PATCH v5 11/18] timer: Split out "get next timer interrupt" functionality
Date: Thu, 9 Mar 2023 18:45:46 +0100 [thread overview]
Message-ID: <ZAobSqZvcHLEKUpl@lothringen> (raw)
In-Reply-To: <ZAoJlEwW/2hX6zlQ@localhost.localdomain>
On Thu, Mar 09, 2023 at 05:30:12PM +0100, Frederic Weisbecker wrote:
> Le Wed, Mar 01, 2023 at 03:17:37PM +0100, Anna-Maria Behnsen a écrit :
> > The functionallity for getting the next timer interrupt in
> > get_next_timer_interrupt() is splitted into a separate function
> > fetch_next_timer_interrupt() to be usable by other callsides.
> >
> > This is preparatory work for the conversion of the NOHZ timer
> > placement to a pull at expiry time model. No functional change.
> >
> > Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
> [...]
> > diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> > index ff41d978cb22..dfc744545159 100644
> > --- a/kernel/time/timer.c
> > +++ b/kernel/time/timer.c
> > @@ -2040,31 +2071,9 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
> > if (time_before(nextevt, basej))
> > nextevt = basej;
> > tevt.local = basem + (u64)(nextevt - basej) * TICK_NSEC;
> > - goto unlock;
> > + tevt.global = KTIME_MAX;
> > }
> >
> > - /*
> > - * If the bases are marked idle, i.e. the next event on both the
> > - * local and the global queue are farther away than a tick,
> > - * evaluate both bases. No need to check whether one of the bases
> > - * has an already expired timer as this is caught by the !is_idle
> > - * condition above.
> > - */
> > - if (base_local->timers_pending)
> > - tevt.local = basem + (u64)(nextevt_local - basej) * TICK_NSEC;
> > -
> > - /*
> > - * If the local queue expires first, then the global event can be
> > - * ignored. The CPU wakes up before that. If the global queue is
> > - * empty, nothing to do either.
> > - */
> > - if (!local_first && base_global->timers_pending)
> > - tevt.global = basem + (u64)(nextevt_global - basej) * TICK_NSEC;
> > -
> > -unlock:
> > - raw_spin_unlock(&base_global->lock);
> > - raw_spin_unlock(&base_local->lock);
> > -
> > tevt.local = min_t(u64, tevt.local, tevt.global);
>
> So if you leave that last line, it means that the CPU will eventually
> and unconditionally wake up for the next global timer if it's before the
> next local timer. Am I understanding this right and, if so, is that intended?
Nevermind, that's removed on the main patch.
Sorry for the noise.
next prev parent reply other threads:[~2023-03-09 17:45 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-01 14:17 [PATCH v5 00/18] timer: Move from a push remote at enqueue to a pull at expiry model Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 01/18] tick-sched: Warn when next tick seems to be in the past Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 02/18] timer: Add comment to get_next_timer_interrupt() description Anna-Maria Behnsen
2023-04-11 9:36 ` Frederic Weisbecker
2023-04-11 16:10 ` Anna-Maria Behnsen
2023-04-12 11:29 ` Frederic Weisbecker
2023-03-01 14:17 ` [PATCH v5 03/18] timer: Move store of next event into __next_timer_interrupt() Anna-Maria Behnsen
2023-03-21 12:48 ` Peter Zijlstra
2023-04-12 11:32 ` Frederic Weisbecker
2023-03-01 14:17 ` [PATCH v5 04/18] timer: Split next timer interrupt logic Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 05/18] timer: Rework idle logic Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 06/18] add_timer_on(): Make sure callers have TIMER_PINNED flag Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 07/18] timers: Ease code in run_local_timers() Anna-Maria Behnsen
2023-04-12 14:32 ` Frederic Weisbecker
2023-03-01 14:17 ` [PATCH v5 08/18] timers: Create helper function to forward timer base clk Anna-Maria Behnsen
2023-04-12 14:40 ` Frederic Weisbecker
2023-03-01 14:17 ` [PATCH v5 09/18] timer: Keep the pinned timers separate from the others Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 10/18] timer: Retrieve next expiry of pinned/non-pinned timers seperately Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 11/18] timer: Split out "get next timer interrupt" functionality Anna-Maria Behnsen
2023-03-09 16:30 ` Frederic Weisbecker
2023-03-09 17:45 ` Frederic Weisbecker [this message]
2023-03-21 14:30 ` Peter Zijlstra
2023-04-12 20:34 ` Frederic Weisbecker
2023-03-01 14:17 ` [PATCH v5 12/18] timer: Add get next timer interrupt functionality for remote CPUs Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 13/18] timer: Restructure internal locking Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 14/18] timer: Check if timers base is handled already Anna-Maria Behnsen
2023-03-21 14:43 ` Peter Zijlstra
2023-03-01 14:17 ` [PATCH v5 15/18] tick/sched: Split out jiffies update helper function Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 16/18] timer: Implement the hierarchical pull model Anna-Maria Behnsen
2023-03-14 13:24 ` Frederic Weisbecker
2023-03-14 14:49 ` Anna-Maria Behnsen
2023-03-14 16:01 ` Frederic Weisbecker
2023-03-21 11:17 ` Frederic Weisbecker
2023-04-04 14:05 ` Anna-Maria Behnsen
2023-04-04 14:32 ` Frederic Weisbecker
2023-03-21 13:25 ` Frederic Weisbecker
2023-04-06 9:12 ` Anna-Maria Behnsen
2023-03-21 15:29 ` Peter Zijlstra
2023-03-21 15:34 ` Peter Zijlstra
2023-03-21 15:40 ` Peter Zijlstra
2023-03-23 9:22 ` Peter Zijlstra
2023-03-23 9:34 ` Peter Zijlstra
2023-03-23 9:47 ` Peter Zijlstra
2023-03-23 12:47 ` Peter Zijlstra
2023-03-23 14:24 ` Peter Zijlstra
2023-04-04 14:56 ` Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 17/18] timer_migration: Add tracepoints Anna-Maria Behnsen
2023-03-01 14:17 ` [PATCH v5 18/18] timer: Always queue timers on the local CPU Anna-Maria Behnsen
2023-03-21 12:46 ` [PATCH v5 00/18] timer: Move from a push remote at enqueue to a pull at expiry model Peter Zijlstra
2023-04-04 13:35 ` Anna-Maria Behnsen
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