Messages in this thread Patch in this message | | | Date | Thu, 8 Mar 2018 16:14:10 +0100 | From | Frederic Weisbecker <> | Subject | Re: [RFC/RFT][PATCH v2 1/6] time: tick-sched: Reorganize idle tick management code |
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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;
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