linux-kernel - Re: [patch 7/7, v7] NUMA Hotplug Emulator: Implement mem_hotplug/add

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Message-ID: <alpine.DEB.2.00.1012021534140.6878@chino.kir.corp.google.com>
Date:	Thu, 2 Dec 2010 15:37:03 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Shaohui Zheng <shaohui.zheng@...el.com>
cc:	Andrew Morton <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, dave@...ux.vnet.ibm.com,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Haicheng Li <haicheng.li@...el.com>
Subject: Re: [patch 7/7, v7] NUMA Hotplug Emulator: Implement mem_hotplug/add_memory
 debugfs interface

On Thu, 2 Dec 2010, shaohui.zheng@...el.com wrote:

> From:  Shaohui Zheng <shaohui.zheng@...el.com>
> 
> Add mem_hotplug/add_memory interface to support to memory hotplug emulation.
> the reserved memory can be added into desired node with this interface.
> 
> Add a memory section(128M) to node 3(boots with mem=1024m)
> 
> 	echo 0x40000000,3 > mem_hotplug/add_memory
> 
> And more we make it friendly, it is possible to add memory to do
> 
> 	echo 3g > mem_hotplug/add_memory
> 	echo 1024m,3 > mem_hotplug/add_memory
> 
> Another format suggested by Dave Hansen:
> 
> 	echo physical_address=0x40000000 numa_node=3 > mem_hotplug/add_memory
> 
> it is more explicit to show meaning of the parameters.
> 

NACK, we don't need such convoluted definitions if debugfs were extended 
with per-node triggers to add_memory as I suggested in v6 of your 
proposal:

	/sys/kernel/debug/mem_hotplug/add_node (already exists)
	/sys/kernel/debug/mem_hotplug/node0/add_memory
	/sys/kernel/debug/mem_hotplug/node1/add_memory
	...

You can then write a physical starting address to the add_memory files to 
hotadd memory to a node other than the one to which it has physical 
affinity.  This is much more extendable if we add additional per-node 
triggers later.

It would also be helpful if you were to reach consensus on the matters 
under discussion before posting a new version of your patchset everyday.
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