linux-kernel - Re: [RFC, 3/7] NUMA hotplug emulator

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Date:	Fri, 21 May 2010 15:38:16 +0530
From:	Ankita Garg <ankita@...ibm.com>
To:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Alex Chiang <achiang@...com>, linux-kernel@...r.kernel.org,
	ak@...ux.intel.co, fengguang.wu@...el.com,
	haicheng.li@...ux.intel.com, shaohui.zheng@...ux.intel.com
Cc:	Balbir Singh <balbir@...ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Subject: Re: [RFC, 3/7] NUMA hotplug emulator

Hi,

On Thu, May 13, 2010 at 07:48:35PM +0800, Shaohui Zheng wrote:
> Userland interface to hotplug-add fake offlined nodes.
> 
> Add a sysfs entry "probe" under /sys/devices/system/node/:
> 
>  - to show all fake offlined nodes:
>     $ cat /sys/devices/system/node/probe
> 
>  - to hotadd a fake offlined node, e.g. nodeid is N:
>     $ echo N > /sys/devices/system/node/probe
> 
> Signed-off-by: Haicheng Li <haicheng.li@...ux.intel.com>
> Signed-off-by: Shaohui Zheng <shaohui.zheng@...el.com>
> ---
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 9458685..2c078c8 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1214,6 +1214,20 @@ config NUMA_EMU
>  	  into virtual nodes when booted with "numa=fake=N", where N is the
>  	  number of nodes. This is only useful for debugging.
> 
> +config NUMA_HOTPLUG_EMU
> +	bool "NUMA hotplug emulator"
> +	depends on X86_64 && NUMA && HOTPLUG
> +	---help---
> +
> +config NODE_HOTPLUG_EMU
> +	bool "Node hotplug emulation"
> +	depends on NUMA_HOTPLUG_EMU && MEMORY_HOTPLUG
> +	---help---
> +	  Enable Node hotplug emulation. The machine will be setup with
> +	  hidden virtual nodes when booted with "numa=hide=N*size", where
> +	  N is the number of hidden nodes, size is the memory size per
> +	  hidden node. This is only useful for debugging.
> +

The above dependencies do not work as expected. I could configure
NUMA_HOTPLUG_EMU & NODE_HOTPLUG_EMU without having MEMORY_HOTPLUG
turned on. By pushing the above definition below SPARSEMEM and memory
hot add and remove, the dependencies could be sorted out.

-- 
Regards,                                                                        
Ankita Garg (ankita@...ibm.com)                                                 
Linux Technology Center                                                         
IBM India Systems & Technology Labs,                                            
Bangalore, India
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