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From: Andi Kleen <ak@suse.de>
To: Mike Travis <travis@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>, Paul Jackson <pj@sgi.com>,
	David Rientjes <rientjes@google.com>,
	Lee.Schermerhorn@hp.com, mel@csn.ul.ie,
	linux-kernel@vger.kernel.org, akpm@linux-foundation.org
Subject: Re: [RFC] bitmap relative operator for mempolicy extensions
Date: Thu, 14 Feb 2008 21:30:05 +0100	[thread overview]
Message-ID: <200802142130.06155.ak@suse.de> (raw)
In-Reply-To: <47B4A3D7.7040007@sgi.com>

On Thursday 14 February 2008 21:25:59 Mike Travis wrote:
> Christoph Lameter wrote:
> > On Thu, 14 Feb 2008, Andi Kleen wrote:
> > 
> >> You're saying the kernel should use these relative masks internally?
> > 
> > There is just some thoughts about this. Did not have time to look into the 
> > details. Mike?
> 
> There are a few places where the entire cpumask is not needed.  For
> example, in the area of core siblings on a node.  There's a limit
> to how many cores/threads can be on a node and the full 4k cpumask
> is not needed.  How this pertains to this new functionality I'm
> not sure yet.

That would require that the BIOS enumerates the CPUs in a way that
the cores of a socket are continuous. While that's usually true
I don't think there's a guarantee. In theory they could be all scattered.

Ok I theory Linux could remap later but that seems hardly worth 
the trouble.

I would rather just use arrays of integers in this case with a reasonable fixed 
upper limit (e.g. 16 or 32 -- if there are ever >32 thread x86 CPUs presumably they will
require an updated cpufreq driver too...) 


-Andi


  reply	other threads:[~2008-02-14 20:30 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-14 12:35 Paul Jackson
2008-02-14 14:11 ` KOSAKI Motohiro
2008-02-14 16:35   ` Paul Jackson
2008-02-14 20:55     ` Ray Lee
2008-02-14 21:16       ` David Rientjes
2008-02-15 10:47         ` Paul Jackson
2008-02-15  0:24       ` KOSAKI Motohiro
2008-02-15 10:25         ` Paul Jackson
2008-02-15 10:58       ` Paul Jackson
2008-02-14 19:27 ` Christoph Lameter
2008-02-14 20:02   ` Andi Kleen
2008-02-14 20:06     ` Christoph Lameter
2008-02-14 20:25       ` Mike Travis
2008-02-14 20:30         ` Andi Kleen [this message]
2008-02-15  9:54     ` Paul Jackson

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