linux-kernel - Re: [PATCH RESEND] smp: make wake up idle cpus more generic

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Date:	Sat, 2 Apr 2016 15:10:40 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Lianwei Wang <lianwei.wang@...il.com>,
	Ingo Molnar <mingo@...nel.org>
Cc:	rjw@...ysocki.net, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, kbuild-all@...org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH RESEND] smp: make wake up idle cpus more generic

On 04/02/2016 08:15 AM, Lianwei Wang wrote:
>>
>> * Lianwei Wang <lianwei.wang@...il.com> wrote:
>>
>>> The wake_up_all_idle_cpus API always wake up all the online
>>> cpus, but sometimes we only want to wake up a set of cpus.
>>> Use a generic function to wake up a group of cpus that is
>>> specified by the cpumask parameter. This generic API can
>>> benefit to the cases that only need to wake up a set of
>>> cpus.
>>
>> What is the new user of this new argument to the wake-up call?
>>
>> Thanks,
>>
>>          Ingo
>
> The ARM big.LITTLE arch is one of the users to use the new wake up
> call. Two clusters in these SoCs and each cluster has 2 or more CPUs.
> For some cases, we only need to wake up the cpus on one cluster, not
> all the cpus. The other cluster can keep in idle state to save power.
> Another use case is that for the threads/irqs that bind to some cpus,
> we also want to wake up the cpus that the threads/irqs bind to, and
> the other cpus can stay in idle state. I'm updating the pm_qos code to
> support binding the request to a set of cpus, and the
> cpuidle_latency_notify call can pass the cpumask parameter to the new
> wake-up call.

Hi Lianwei,

a quick suggestion : cpuidle_driver->cpumask

   -- Daniel


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