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From: Quentin Perret <quentin.perret@arm.com>
To: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: peterz@infradead.org, mingo@redhat.com,
	valentin.schneider@arm.com, dietmar.eggemann@arm.com,
	vincent.guittot@linaro.org, gaku.inami.xh@renesas.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCHv3 1/9] sched: Add static_key for asymmetric cpu capacity optimizations
Date: Fri, 22 Jun 2018 09:22:22 +0100	[thread overview]
Message-ID: <20180622082222.GD23168@e108498-lin.cambridge.arm.com> (raw)
In-Reply-To: <1529485549-5191-2-git-send-email-morten.rasmussen@arm.com>

Hi Morten,

On Wednesday 20 Jun 2018 at 10:05:41 (+0100), Morten Rasmussen wrote:
> +static void update_asym_cpucapacity(int cpu)
> +{
> +	int enable = false;
> +
> +	rcu_read_lock();
> +	if (lowest_flag_domain(cpu, SD_ASYM_CPUCAPACITY))
> +		enable = true;
> +	rcu_read_unlock();
> +
> +	if (enable) {
> +		/* This expects to be hotplug-safe */
> +		static_branch_enable_cpuslocked(&sched_asym_cpucapacity);
> +	}
> +}

What would happen if you hotplugged an entire cluster ? You'd loose the
SD_ASYM_CPUCAPACITY flag but keep the static key is that right ? Should
we care ?

And also, Peter mentioned an issue with the EAS patches with multiple
root_domains. Does that apply here as well ? What if you had a
configuration with big and little CPUs in different root_domains for ex?

Should we disable the static key in the above cases ?

Thanks,
Quentin

  reply	other threads:[~2018-06-22  8:22 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-20  9:05 [PATCHv3 0/9] sched/fair: Migrate 'misfit' tasks on asymmetric capacity systems Morten Rasmussen
2018-06-20  9:05 ` [PATCHv3 1/9] sched: Add static_key for asymmetric cpu capacity optimizations Morten Rasmussen
2018-06-22  8:22   ` Quentin Perret [this message]
2018-06-22 14:36     ` Morten Rasmussen
2018-06-27 15:41       ` Dietmar Eggemann
2018-06-28  8:48         ` Morten Rasmussen
2018-06-28 17:16           ` Dietmar Eggemann
2018-07-02  8:36             ` Morten Rasmussen
2018-06-20  9:05 ` [PATCHv3 2/9] sched/fair: Add group_misfit_task load-balance type Morten Rasmussen
2018-06-20  9:05 ` [PATCHv3 3/9] sched: Add sched_group per-cpu max capacity Morten Rasmussen
2018-06-20  9:05 ` [PATCHv3 4/9] sched/fair: Consider misfit tasks when load-balancing Morten Rasmussen
2018-06-20  9:05 ` [PATCHv3 5/9] sched/fair: Kick nohz balance if rq->misfit_task Morten Rasmussen
2018-06-20  9:05 ` [PATCHv3 6/9] sched: Change root_domain->overload type to int Morten Rasmussen
2018-06-20  9:05 ` [PATCHv3 7/9] sched: Wrap rq->rd->overload accesses with READ/WRITE_ONCE Morten Rasmussen
2018-06-20  9:05 ` [PATCHv3 8/9] sched/fair: Set sd->overload when misfit Morten Rasmussen
2018-06-20  9:05 ` [PATCHv3 9/9] sched/fair: Don't move tasks to lower capacity cpus unless necessary Morten Rasmussen
2018-07-03  2:28 ` [PATCHv3 0/9] sched/fair: Migrate 'misfit' tasks on asymmetric capacity systems Gaku Inami
2018-07-04 10:33   ` Morten Rasmussen

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