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Date: Thu, 17 May 2007 11:01:01 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
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To: Peter Zijlstra <a.p.zijlstra@chello.nl>
cc: Matt Mackall <mpm@selenic.com>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org, Thomas Graf <tgraf@suug.ch>,
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       Andrew Morton <akpm@linux-foundation.org>,
       Daniel Phillips <phillips@google.com>,
       Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [PATCH 0/5] make slab gfp fair
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On Thu, 17 May 2007, Peter Zijlstra wrote:

> > > Its about ensuring ALLOC_NO_WATERMARKS memory only reaches PF_MEMALLOC
> > > processes, not joe random's pi calculator.
> > 
> > Watermarks are per zone?
> 
> Yes, but the page allocator might address multiple zones in order to
> obtain a page.

And then again it may not because the allocation is contrained to a 
particular node,a NORMAL zone or a DMA zone. One zone way be below the 
watermark and another may not. Different allocations may be allowed to 
tap into various zones for various reasons.