linux-kernel - Re: [PATCH 0/5] make slab gfp fair

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Message-Id: <20070514124451.c868c4c0.akpm@linux-foundation.org>
Date:	Mon, 14 May 2007 12:44:51 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Matt Mackall <mpm@...enic.com>
Cc:	Christoph Lameter <clameter@....com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Thomas Graf <tgraf@...g.ch>,
	David Miller <davem@...emloft.net>,
	Daniel Phillips <phillips@...gle.com>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 0/5] make slab gfp fair

On Mon, 14 May 2007 11:12:24 -0500
Matt Mackall <mpm@...enic.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?
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