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Date: Tue, 23 Nov 2010 00:04:12 +0800
From: =?utf-8?Q?Am=C3=A9rico?= Wang <xiyou.wangcong@gmail.com>
To: Shaohui Zheng <shaohui.zheng@intel.com>
Cc: =?utf-8?Q?Am=C3=A9rico?= Wang <xiyou.wangcong@gmail.com>,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, haicheng.li@linux.intel.com,
        lethal@linux-sh.org, ak@linux.intel.com, shaohui.zheng@linux.intel.com,
        Haicheng Li <haicheng.li@intel.com>
Subject: Re: [8/8,v3] NUMA Hotplug Emulator: documentation
Message-ID: <20101122160412.GE4137@hack>
References: <20101117020759.016741414@intel.com> <20101117021000.985643862@intel.com> <20101121150344.GK9099@hack> <20101121233351.GA7626@shaohui>
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On Mon, Nov 22, 2010 at 07:33:51AM +0800, Shaohui Zheng wrote:
>On Sun, Nov 21, 2010 at 11:03:45PM +0800, Américo Wang wrote:
>> 
>> >From your documentation above, it looks like you are trying
>> to move one CPU between nodes?
>Yes, you are correct. With cpu probe/release interface, you can hot-remove a
>CPU from a node, and hot-add it to another node.


Can I also move the CPU to another node _after_ it is hot-added?
Or I have to hot-remove it first and then hot-add it again?

>> 
>> >+	cpu_hpe=on/off
>> >+		Enable/disable cpu hotplug emulation with software method. when cpu_hpe=on,
>> >+		sysfs provides probe/release interface to hot add/remove cpu dynamically.
>> >+		this option is disabled in default.
>> >+			
>> 
>> Why not just a CONFIG? IOW, why do we need to make another boot
>> parameter for this?
>Only the developer or QA will use the emulator, we did not want to change the
>default action for common user who does not care the hotplug emulator, so we
>use a kernel parameter as a switch. The common user is not aware the existence
>of the emulator.
>

I think it is also useful to other Linux users, e.g. after I
boot with "maxcpus=1", I can still bring the rest 3 CPU's
back without reboot.

Thanks.

-- 
Live like a child, think like the god.
 
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