linux-kernel - Re: [RFC PATCH V3 0/3] PM/CPU: Parallel enalbing nonboot cpus with resume devices

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Message-ID: <5447495A.1060102@intel.com>
Date:	Wed, 22 Oct 2014 14:06:18 +0800
From:	Lan Tianyu <tianyu.lan@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	mingo@...nel.org, rafael.j.wysocki@...el.com, toshi.kani@...com,
	akpm@...ux-foundation.org, ktkhai@...allels.com, fabf@...net.be,
	laijs@...fujitsu.com, srivatsa.bhat@...ux.vnet.ibm.com,
	ego@...ux.vnet.ibm.com, srivatsa@....edu, viresh.kumar@...aro.org,
	todd.e.brandt@...ux.intel.com, tipbot@...or.com,
	wangyun@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH V3 0/3] PM/CPU: Parallel enalbing nonboot cpus with
 resume devices

On 2014年10月09日 09:18, Lan Tianyu wrote:
> On 2014年10月09日 04:54, Peter Zijlstra wrote:
>> On Thu, Sep 25, 2014 at 04:32:02PM +0800, Lan Tianyu wrote:
>>> This patchset is to parallel enabling nonboot cpus with resuming devices
>>> during system resume in order to accelerate S2RAM. From test result on
>>> a 8 logical core Haswell machine, system resume time reduces from 347ms
>>> to 217ms with this patchset.
>>>
>>> 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 wastes cpu usage.
>>>
>>> This patchset is to allow boot cpu to go forward to resume devices after
>>> bringing up one nonboot cpu and starting a thread. The thread will be in
>>> charge of bringing up other frozen cpus. The thread will be scheduled to
>>> the first online cpu to run . This makes enabling cpu2~x parallel with
>>> resuming devices.
>>
>> So I feel we should really clean up hotplug before doing anything like
>> this. Its a trainwreck and just piling more and more hacks ontop isn't
>> going to help any.
>>
> 
> Hi Peter:
> 	Sorry, I don't know the gap of hotplug clearly. Could you elaborate it?
> 

Hi Peter:
	Could you elaborate the gap of hotplug? Thanks.

-- 
Best regards
Tianyu Lan
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