linux-kernel - Re: + fix-spellings-of-slab-allocator-section-in-init-kconfig.patch added to -mm tree

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Date:	Wed, 09 May 2007 13:04:09 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Christoph Lameter <clameter@....com>
CC:	Matt Mackall <mpm@...enic.com>, akpm@...ux-foundation.org,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org
Subject: Re: + fix-spellings-of-slab-allocator-section-in-init-kconfig.patch
 added to -mm tree

Christoph Lameter wrote:
> On Wed, 9 May 2007, Nick Piggin wrote:

>>For small systems, I would not be surprised if that was less space
>>efficient, even just looking at kmalloc caches in isolation. Or do you
>>have numbers to support your conclusion?
> 
> 
> No I do not have any number beyond the efficiency calculations based on 
> whole slabs. We would have to do some experiments to figure out how much 
> space is actually wasted through partial slabs.
> 
> If you just do straight allocation on a UP system then there is at maximum 
> one partial slab per slabcache with SLUB.
> 
> The situation becomes different with allocation and frees. Then we may 
> have lots of partial slabs that we allocate from.

Yeah, but even then I think the SLUB approach is a very nice one for a
general purpose system. Don't get me wrong, SLOB definitely is not good
for that :)


> But the SLOB approach 
> also will have holes to manage. So I do not see how this could be a 
> benefit unless you only have a few precious pages and you need to put 
> multiple object sizes into it. A 4M system still has 1000 pages.

Right, and it takes a long long time to do anything on my 4G system ;)

But that 4MB system might not even have 50 pages that you'd want to
use for slab.

-- 
SUSE Labs, Novell Inc.
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