From: Peter Zijlstra <peterz@infradead.org>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: Aubrey Li <aubrey.li@linux.intel.com>,
mingo@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, mgorman@techsingularity.net,
qais.yousef@arm.com, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com,
tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org,
Mel Gorman <mgorman@suse.de>, Jiang Biao <benbjiang@gmail.com>
Subject: Re: [RFC PATCH v5] sched/fair: select idle cpu from idle cpumask for task wakeup
Date: Mon, 7 Dec 2020 19:05:18 +0100 [thread overview]
Message-ID: <20201207180518.GR3040@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <jhjtusxtv7b.mognet@arm.com>
On Mon, Dec 07, 2020 at 04:52:24PM +0000, Valentin Schneider wrote:
>
> On 07/12/20 15:48, Peter Zijlstra wrote:
> > On Wed, Nov 18, 2020 at 12:31:13PM +0800, Aubrey Li wrote:
> >> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> >> index f324dc36fc43..6f5947673e66 100644
> >> --- a/kernel/sched/idle.c
> >> +++ b/kernel/sched/idle.c
> >> @@ -163,6 +163,7 @@ static void cpuidle_idle_call(void)
> >> */
> >>
> >> if (cpuidle_not_available(drv, dev)) {
> >> + update_idle_cpumask(this_rq(), true);
> >> tick_nohz_idle_stop_tick();
> >>
> >> default_idle_call();
> >> @@ -193,6 +194,7 @@ static void cpuidle_idle_call(void)
> >> max_latency_ns = dev->forced_idle_latency_limit_ns;
> >> }
> >>
> >> + update_idle_cpumask(this_rq(), true);
> >> tick_nohz_idle_stop_tick();
> >>
> >> next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns);
> >> @@ -205,10 +207,12 @@ static void cpuidle_idle_call(void)
> >> */
> >> next_state = cpuidle_select(drv, dev, &stop_tick);
> >>
> >> - if (stop_tick || tick_nohz_tick_stopped())
> >> + if (stop_tick || tick_nohz_tick_stopped()) {
> >> + update_idle_cpumask(this_rq(), true);
> >> tick_nohz_idle_stop_tick();
> >
> > We already have a callback in tick_nohz_idle_stop_tick(), namely
> > nohz_balance_enter_idle().
>
> That's a no-op for !NO_HZ_COMMON though. For similar reasons, Aubrey moved
> the clearing of the cpumask to scheduler_tick().
>
> Are you saying this mechanism should only be driven for NO_HZ kernels?
IFF it keys off of the tick being stopped, then yes. But as said in the
other email, I think that's a very dubious thing to begin with.
next prev parent reply other threads:[~2020-12-07 18:06 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-18 4:31 [RFC PATCH v5] sched/fair: select idle cpu from idle cpumask for task wakeup Aubrey Li
2020-11-23 9:27 ` Vincent Guittot
2020-11-24 7:01 ` Li, Aubrey
2020-11-24 17:01 ` Vincent Guittot
2020-11-25 2:03 ` Li, Aubrey
2020-11-25 8:31 ` Vincent Guittot
2020-11-25 13:37 ` Li, Aubrey
2020-11-26 8:14 ` Vincent Guittot
2020-11-26 9:35 ` Li, Aubrey
2020-11-26 9:49 ` Vincent Guittot
2020-12-07 15:48 ` Peter Zijlstra
2020-12-07 16:52 ` Valentin Schneider
2020-12-07 18:05 ` Peter Zijlstra [this message]
2020-12-07 15:50 ` Peter Zijlstra
2020-12-07 17:10 ` Mel Gorman
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