linux-kernel - Re: [patch 1/2] x86: add numa=possible command line option

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Message-ID: <alpine.DEB.2.00.1011211343350.26304@chino.kir.corp.google.com>
Date:	Sun, 21 Nov 2010 13:46:07 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
cc:	Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Shaohui Zheng <shaohui.zheng@...el.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Haicheng Li <haicheng.li@...el.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Subject: Re: [patch 1/2] x86: add numa=possible command line option

On Sun, 21 Nov 2010, Américo Wang wrote:

> I am not sure how much value of making this dynamic,
> for CPU, we do this at compile time, i.e. NR_CPUS,
> so how about NR_NODES?
> 

This is outside the scope of node hotplug emulation, it needs to be built 
on top of whatever the kernel implements.

> Also, numa=possible= is not as clear as numa=max=, for me at least.
> 

I like name, but it requires that you know how many nodes that system 
already has.  In other words, numa=possible=4 allows you to specify that 4 
additional nodes will be possible, but initially offline, for this or 
other purposes.  numa=max=4 would be no-op if the system actually had 4 
nodes.

I chose numa=possible over numa=additional because it is more clearly tied 
to node_possible_map, which is the only thing it modifies.