linux-kernel - Re: [5/8,v3] NUMA Hotplug Emulator: support cpu probe/release in x86

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Date:	Tue, 23 Nov 2010 07:29:46 +0800
From:	Shaohui Zheng <shaohui.zheng@...el.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
Cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, haicheng.li@...ux.intel.com,
	lethal@...ux-sh.org, ak@...ux.intel.com,
	shaohui.zheng@...ux.intel.com, Ingo Molnar <mingo@...e.hu>,
	Len Brown <len.brown@...el.com>,
	Yinghai Lu <Yinghai.Lu@....COM>,
	Haicheng Li <haicheng.li@...el.com>
Subject: Re: [5/8,v3] NUMA Hotplug Emulator: support cpu probe/release in
 x86

On Mon, Nov 22, 2010 at 11:51:52PM +0800, Américo Wang wrote:
> On Mon, Nov 22, 2010 at 08:01:04AM +0800, Shaohui Zheng wrote:
> >On Sun, Nov 21, 2010 at 10:45:11PM +0800, Américo Wang wrote:
> >> On Wed, Nov 17, 2010 at 10:08:04AM +0800, shaohui.zheng@...el.com wrote:
> >> >From: Shaohui Zheng <shaohui.zheng@...el.com>
> >> >
> >> >Add cpu interface probe/release under sysfs for x86. User can use this
> >> >interface to emulate the cpu hot-add process, it is for cpu hotplug 
> >> >test purpose. Add a kernel option CONFIG_ARCH_CPU_PROBE_RELEASE for this
> >> >feature.
> >> >
> >> >This interface provides a mechanism to emulate cpu hotplug with software
> >> > methods, it becomes possible to do cpu hotplug automation and stress
> >> >testing.
> >> >
> >> 
> >> Huh? We already have CPU online/offline...
> >> 
> >> Can you describe more about the difference?
> >> 
> >> Thanks.
> >
> >Again, we already try to discribe the difference between logcial cpu
> >online/offline and physical cpu online/offline many times.
> >
> 
> I see, with "maxcpus=" we will only have the specified number
> of CPU's which can be online/offline, you are trying to bring
> the rest of CPU's hidden by "maxcpus=". :) Correct?
Yes, when we online the rest CPUs, it test our cpu hot-add code logical.
> 
> I think the idea is cool, but I think you need to improve
> the documetion, for people who don't follow the hardware
> concepts like me. ;)
CPU hot-add is supported by only a few hardwares, so many users might never 
see such hardware, we should document it better. thanks for the remind.
> 
> Thanks.
> 
> -- 
> Live like a child, think like the god.
>  

-- 
Thanks & Regards,
Shaohui

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