linux-kernel - Re: [RFC PATCH] PM/CPU: Parallel enabling nonboot cpus with resume devices

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Message-ID: <20140723105304.GA22675@amd.pavel.ucw.cz>
Date:	Wed, 23 Jul 2014 12:53:04 +0200
From:	Pavel Machek <pavel@....cz>
To:	Lan Tianyu <tianyu.lan@...el.com>
Cc:	rjw@...ysocki.net, len.brown@...el.com, peterz@...radead.org,
	toshi.kani@...com, mingo@...nel.org, akpm@...ux-foundation.org,
	todd.e.brandt@...ux.intel.com, fabf@...net.be,
	srivatsa.bhat@...ux.vnet.ibm.com, ego@...ux.vnet.ibm.com,
	rafael.j.wysocki@...el.com, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [RFC PATCH] PM/CPU: Parallel enabling nonboot cpus with resume
 devices

Hi!

> In the current world, all nonboot cpus are enabled serially during system
> resume. System resume sequence is that boot cpu enables nonboot cpu one by
> one and then resume devices. Before resuming devices, there are few tasks
> assigned to nonboot cpus after they are brought up. This waste cpu usage.
> 
> To accelerate S3, this patches adds a new kernel configure
> PM_PARALLEL_CPU_UP_FOR_SUSPEND to allow boot cpu to go forward to resume
> devices after bringing up one nonboot cpu. The nonboot cpu will be in charge
> of bringing up other cpus. This makes enabling cpu2~x parallel with resuming
> devices. From the test result on 4 logical core laptop, the time of resume
> device almost wasn't affected by enabling nonboot cpus lately while the start
> point is almost 30ms earlier than before.

Does this mean that userspace can now run seeing the "offlined" cpus
still in offline state?

									Pavel

-- 
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