linux-kernel - Re: [RFC Patch V1 00/30] Enable memoryless node on x86 platforms

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Message-ID: <53C07865.2040103@zytor.com>
Date:	Fri, 11 Jul 2014 16:51:01 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>,
	Greg KH <gregkh@...uxfoundation.org>
CC:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Tony Luck <tony.luck@...el.com>, linux-mm@...ck.org,
	linux-hotplug@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC Patch V1 00/30] Enable memoryless node on x86 platforms

On 07/11/2014 01:20 PM, Andi Kleen wrote:
> Greg KH <gregkh@...uxfoundation.org> writes:
> 
>> On Fri, Jul 11, 2014 at 10:29:56AM +0200, Peter Zijlstra wrote:
>>> On Fri, Jul 11, 2014 at 03:37:17PM +0800, Jiang Liu wrote:
>>>> Any comments are welcomed!
>>>
>>> Why would anybody _ever_ have a memoryless node? That's ridiculous.
>>
>> I'm with Peter here, why would this be a situation that we should even
>> support?  Are there machines out there shipping like this?
> 
> We've always had memory nodes.
> 
> A classic case in the old days was a two socket system where someone
> didn't populate any DIMMs on the second socket.
> 
> There are other cases too.
> 

Yes, like a node controller-based system where the system can be
populated with either memory cards or CPU cards, for example.  Now you
can have both memoryless nodes and memory-only nodes...

Memory-only nodes also happen in real life.  In some cases they are done
by permanently putting low-frequency CPUs to sleep for their memory
controllers.
	
	-hpa


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