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Message-ID: <20221108104738.GA21669@lothringen>
Date: Tue, 8 Nov 2022 11:47:38 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Anna-Maria Behnsen <anna-maria@...utronix.de>
Cc: linux-kernel@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>,
John Stultz <jstultz@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Eric Dumazet <edumazet@...gle.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
Arjan van de Ven <arjan@...radead.org>,
"Paul E . McKenney" <paulmck@...nel.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH v4 14/16] timer: Implement the hierarchical pull model
On Fri, Nov 04, 2022 at 03:57:35PM +0100, Anna-Maria Behnsen wrote:
> @@ -1859,6 +1863,36 @@ void forward_and_idle_timer_bases(unsigned long basej, u64 basem,
> */
> is_idle = time_after(nextevt, basej + 1);
>
> + if (is_idle) {
> + u64 next_tmigr;
> +
> + next_tmigr = tmigr_cpu_deactivate(tevt->global);
> +
> + tevt->global = KTIME_MAX;
> +
> + /*
> + * If CPU is the last going idle in timer migration
> + * hierarchy, make sure CPU will wake up in time to handle
> + * remote timers. next_tmigr == KTIME_MAX if other CPUs are
> + * still active.
> + */
> + if (next_tmigr < tevt->local) {
> + u64 tmp;
> +
> + /* If we missed a tick already, force 0 delta */
> + if (next_tmigr < basem)
> + next_tmigr = basem;
> +
> + tmp = div_u64(next_tmigr - basem, TICK_NSEC);
> +
> + nextevt = basej + (unsigned long)tmp;
> + tevt->local = next_tmigr;
> + is_idle = time_after(nextevt, basej + 1);
So after that, tevt->global shouldn't matter anymore for tick_nohz_next_event(),
right? If so then probably that line can go away (with a comment specifying why we can
ignore the global part)?:
tevt.local = min_t(u64, tevt.local, tevt.global);
Thanks.
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