From: Valentin Schneider <valentin.schneider@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>,
mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de, fweisbec@gmail.com,
tglx@linutronix.de, bristot@redhat.com,
linux-kernel@vger.kernel.org, joel@joelfernandes.org
Cc: qais.yousef@arm.com, Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: [PATCH 1/6] sched/fair: remove update of blocked load from newidle_balance
Date: Tue, 09 Feb 2021 13:09:20 +0000 [thread overview]
Message-ID: <jhjv9b1tmkf.mognet@arm.com> (raw)
In-Reply-To: <20210205114830.781-2-vincent.guittot@linaro.org>
On 05/02/21 12:48, Vincent Guittot wrote:
> @@ -10517,16 +10499,11 @@ static void nohz_newidle_balance(struct rq *this_rq)
> time_before(jiffies, READ_ONCE(nohz.next_blocked)))
> return;
>
I was wondering whether all the conditions above were still relevant. I
think they are, but this one:
/* Will wake up very soon. No time for doing anything else*/
if (this_rq->avg_idle < sysctl_sched_migration_cost)
return;
should have its comment updated to something like:
/*
* Will wake up very soon. Blocked load will be updated
* periodically, no need to wake an idle CPU.
*/
given kick_ilb() isn't the costliest of things.
> - raw_spin_unlock(&this_rq->lock);
> /*
> - * This CPU is going to be idle and blocked load of idle CPUs
> - * need to be updated. Run the ilb locally as it is a good
> - * candidate for ilb instead of waking up another idle CPU.
> - * Kick an normal ilb if we failed to do the update.
> + * Blocked load of idle CPUs need to be updated.
> + * Kick an ILB to update statistics.
> */
> - if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE))
> - kick_ilb(NOHZ_STATS_KICK);
> - raw_spin_lock(&this_rq->lock);
With this change, the return value of _nohz_idle_balance() is no longer
used. This means we could get rid of the tracking of whether it iterated
over all nohz CPUs or not.
> + kick_ilb(NOHZ_STATS_KICK);
> }
>
> #else /* !CONFIG_NO_HZ_COMMON */
next prev parent reply other threads:[~2021-02-09 13:10 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-05 11:48 [PATCH 0/6] move update blocked load outside newidle_balance Vincent Guittot
2021-02-05 11:48 ` [PATCH 1/6] sched/fair: remove update of blocked load from newidle_balance Vincent Guittot
2021-02-09 13:09 ` Valentin Schneider [this message]
2021-02-09 13:20 ` Vincent Guittot
2021-02-09 13:44 ` Dietmar Eggemann
2021-02-05 11:48 ` [PATCH 2/6] sched/fair: remove unused parameter of update_nohz_stats Vincent Guittot
2021-02-09 13:45 ` Dietmar Eggemann
2021-02-09 17:38 ` Vincent Guittot
2021-02-05 11:48 ` [PATCH 3/6] sched/fair: merge for each idle cpu loop of ILB Vincent Guittot
2021-02-09 13:09 ` Valentin Schneider
2021-02-05 11:48 ` [PATCH 4/6] sched/fair: reorder newidle_balance pulled_task test Vincent Guittot
2021-02-09 13:46 ` Dietmar Eggemann
2021-02-05 11:48 ` [RFC PATCH 5/6] sched/fair: trigger the update of blocked load on newly idle cpu Vincent Guittot
2021-02-09 13:09 ` Valentin Schneider
2021-02-09 13:57 ` Vincent Guittot
2021-02-09 17:25 ` Valentin Schneider
2021-02-09 13:47 ` Dietmar Eggemann
2021-02-09 14:22 ` Vincent Guittot
2021-02-05 11:48 ` [PATCH 6/6] sched/fair: reduce the window for duplicated update Vincent Guittot
2021-02-05 16:13 ` [PATCH 6/6 v2] " Vincent Guittot
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