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Date: Thu, 18 Nov 2010 13:31:45 -0800 (PST)
From: David Rientjes <rientjes@google.com>
To: Shaohui Zheng <shaohui.zheng@intel.com>
cc: Dave Hansen <dave@linux.vnet.ibm.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>,
        Wu Fengguang <fengguang.wu@intel.com>, Greg KH <greg@kroah.com>
Subject: Re: [7/8,v3] NUMA Hotplug Emulator: extend memory probe interface
 to support NUMA
In-Reply-To: <20101118044850.GC2408@shaohui>
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References: <20101117020759.016741414@intel.com> <20101117021000.916235444@intel.com> <1290019807.9173.3789.camel@nimitz> <alpine.DEB.2.00.1011171312590.10254@chino.kir.corp.google.com> <20101118044850.GC2408@shaohui>
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On Thu, 18 Nov 2010, Shaohui Zheng wrote:

> > Then, export the amount of memory that is actually physically present in 
> > the e820 but was truncated by mem= and allow users to hot-add the memory 
> > via the probe interface.  Add a writeable 'node' file to offlined memory 
> > section directories and allow it to be changed prior to online.
> 
> for memory offlining, it is a known diffcult thing, and it is not supported 
> well in current kernel, so I do not suggest to provide the offline interface
> in the emulator, it just take more pains. We can consider to add it when
> the memory offlining works well.
> 

You're referring to the inability to remove memory sections for 
CONFIG_SPARSEMEM_VMEMMAP?  You should still able to test the offlining 
with other memory models of emulated nodes by using the generic support 
already implemented for CONFIG_MEMORY_HOTREMOVE; the short answer is that 
it probably shouldn't matter at all since we already support node 
hot-remove and the fact that they are emulated nodes isn't really of 
interest.
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