linux-kernel - Re: [patch 00/41] cpu alloc / cpu ops v3: Optimize per cpu access

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Date:	Fri, 30 May 2008 07:38:33 -0700
From:	Mike Travis <travis@....com>
To:	Christoph Lameter <clameter@....com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <dada1@...mosbay.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [patch 00/41] cpu alloc / cpu ops v3: Optimize per cpu access

Christoph Lameter wrote:
> On Thu, 29 May 2008, Andrew Morton wrote:
...
>> Plus who knows what lies ahead of us?
> 
> Well invariably we will end up with cpu area defragmentation.... Sigh.
> 
>> I don't think there is presently any upper limit on alloc_percpu()?  It
>> uses kmalloc() and kmalloc_node()?
>>
>> Even if there is some limit, is it an unfixable one?
> 
> No there is no limit. It just wastes lots of space (pointer arrays, 
> alignment etc) that we could use to configure sufficiently large per cpu 
> areas.

Is there any reason why the per_cpu area couldn't be made extensible?  Maybe
a simple linked list of available areas?  (And use a config variable and/or
boot param for initial size and increment size?)  [Ignoring the problem of
reclaiming the space...]
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