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Date: Mon, 14 May 2007 12:44:51 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Matt Mackall <mpm@selenic.com>
Cc: Christoph Lameter <clameter@sgi.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org, Thomas Graf <tgraf@suug.ch>,
       David Miller <davem@davemloft.net>,
       Daniel Phillips <phillips@google.com>,
       Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [PATCH 0/5] make slab gfp fair
Message-Id: <20070514124451.c868c4c0.akpm@linux-foundation.org>
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On Mon, 14 May 2007 11:12:24 -0500
Matt Mackall <mpm@selenic.com> wrote:

> If I understand this correctly:
> 
> privileged thread                      unprivileged greedy process
> kmem_cache_alloc(...)
>    adds new slab page from lowmem pool
> do_io()
>                                        kmem_cache_alloc(...)
>                                        kmem_cache_alloc(...)
>                                        kmem_cache_alloc(...)
>                                        kmem_cache_alloc(...)
>                                        kmem_cache_alloc(...)
>                                        ...
>                                           eats it all
> kmem_cache_alloc(...) -> ENOMEM
>    who ate my donuts?!

Yes, that's my understanding also.

I can see why it's a problem in theory, but I don't think Peter has yet
revealed to us why it's a problem in practice.  I got all excited when
Christoph asked "I am not sure what the point of all of this is.", but
Peter cunningly avoided answering that ;)

What observed problem is being fixed here?