From: Frederic Weisbecker <frederic@kernel.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
Linux PM <linux-pm@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Thomas Ilsche <thomas.ilsche@tu-dresden.de>,
Doug Smythies <dsmythies@telus.net>,
Rik van Riel <riel@surriel.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
Mike Galbraith <mgalbraith@suse.de>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC/RFT][PATCH v2 1/6] time: tick-sched: Reorganize idle tick management code
Date: Thu, 8 Mar 2018 16:14:10 +0100 [thread overview]
Message-ID: <20180308151407.GA11118@lerouge> (raw)
In-Reply-To: <1938066.lrFpnYERYl@aspire.rjw.lan>
On Thu, Mar 08, 2018 at 10:22:26AM +0100, Rafael J. Wysocki wrote:
> On Thursday, March 8, 2018 12:18:29 AM CET Frederic Weisbecker wrote:
> > On Tue, Mar 06, 2018 at 10:02:01AM +0100, Rafael J. Wysocki wrote:
> > > Index: linux-pm/kernel/time/tick-sched.c
> > > ===================================================================
> > > --- linux-pm.orig/kernel/time/tick-sched.c
> > > +++ linux-pm/kernel/time/tick-sched.c
> > > +
> > > +/**
> > > + * tick_nohz_idle_prepare - prepare for entering idle on the current CPU.
> > > + *
> > > + * Called when we start the idle loop.
> > > + */
> > > +void tick_nohz_idle_prepare(void)
> > > +{
> > > + struct tick_sched *ts;
> > > +
> > > + __tick_nohz_idle_prepare();
> > > +
> > > + local_irq_disable();
> > > +
> > > + ts = this_cpu_ptr(&tick_cpu_sched);
> > > + ts->inidle = 1;
> > > +
> > > + local_irq_enable();
> > > +}
> >
> > Why not calling tick_nohz_start_idle() from there? This is going to
> > simplify the rest, you won't need to call tick_nohz_idle_go_idle()
> > from places that don't want to stop the tick and you can then remove
> > the stop_tick argument.
>
> So I guess I would then use ts->idle_entrytime as "now" in the
> tick_nohz_get_sleep_length() computation, right?
Ah right, I missed the need for ktime_get().
You can't use ts->idle_entrytime in tick_nohz_get_sleep_length() because
full dynticks doesn't rely on it.
But I think you can just do the following, with a comment explaining that
idle_entrytime is expected to be fresh enough at this point:
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 57b3de4..8e61796 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -923,7 +923,7 @@ static void __tick_nohz_idle_enter(struct tick_sched *ts, bool stop_tick)
ts->idle_calls++;
- expires = tick_nohz_stop_sched_tick(ts, now, cpu);
+ expires = tick_nohz_stop_sched_tick(ts, ts->idle_entrytime, cpu);
if (expires > 0LL) {
ts->idle_sleeps++;
ts->idle_expires = expires;
next prev parent reply other threads:[~2018-03-08 15:14 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-06 8:57 [RFC/RFT][PATCH v2 0/6] sched/cpuidle: Idle loop rework Rafael J. Wysocki
2018-03-06 9:02 ` [RFC/RFT][PATCH v2 1/6] time: tick-sched: Reorganize idle tick management code Rafael J. Wysocki
2018-03-07 23:18 ` Frederic Weisbecker
2018-03-08 9:22 ` Rafael J. Wysocki
2018-03-08 15:14 ` Frederic Weisbecker [this message]
2018-03-08 16:34 ` Rafael J. Wysocki
2018-03-08 17:00 ` Frederic Weisbecker
2018-03-06 9:02 ` [RFC/RFT][PATCH v2 2/6] sched: idle: Do not stop the tick upfront in the idle loop Rafael J. Wysocki
2018-03-07 23:39 ` Frederic Weisbecker
2018-03-08 9:05 ` Rafael J. Wysocki
2018-03-06 9:03 ` [RFC/RFT][PATCH v2 3/6] sched: idle: Do not stop the tick before cpuidle_idle_call() Rafael J. Wysocki
2018-03-06 9:05 ` [RFC/RFT][PATCH v2 4/6] cpuidle: Return nohz hint from cpuidle_select() Rafael J. Wysocki
2018-03-06 9:28 ` Rafael J. Wysocki
2018-03-06 10:06 ` [Update][RFC/RFT][PATCH " Rafael J. Wysocki
2018-03-06 9:10 ` [RFC/RFT][PATCH v2 5/6] sched: idle: Select idle state before stopping the tick Rafael J. Wysocki
2018-03-06 9:10 ` [RFC/RFT][PATCH v2 6/6] time: tick-sched: Avoid running the same code twice in a row Rafael J. Wysocki
2018-03-08 10:31 ` [RFC/RFT][PATCH v2 0/6] sched/cpuidle: Idle loop rework Mike Galbraith
2018-03-08 11:10 ` Rafael J. Wysocki
2018-03-08 13:40 ` Mike Galbraith
2018-03-09 9:58 ` Rafael J. Wysocki
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