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Date: Thu, 17 May 2007 12:24:54 -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:

> The proposed patch doesn't change how the kernel functions at this
> point; it just enforces an existing rule better.

Well I'd say it controls the allocation failures. And that only works if 
one can consider the system having a single zone.

Lets say the system has two cpusets A and B. A allocs from node 1 and B 
allocs from node 2. Two processes one in A and one in B run on the same 
processor.

Node 1 gets very low in memory so your patch kicks in and sets up the 
global memory emergency situation with the reserve slab.

Now the process in B will either fail although it has plenty of memory on 
node 2.

Or it may just clear the emergency slab and then the next critical alloc 
of the process in A that is low on memory will fail.