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Date: Wed, 4 Feb 2009 10:49:46 -0500 (EST)
From: Christoph Lameter <cl@linux-foundation.org>
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To: Nick Piggin <nickpiggin@yahoo.com.au>
cc: Mel Gorman <mel@csn.ul.ie>, Pekka Enberg <penberg@cs.helsinki.fi>,
       Nick Piggin <npiggin@suse.de>,
       Linux Memory Management List <linux-mm@kvack.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Lin Ming <ming.m.lin@intel.com>,
       "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Subject: Re: [patch] SLQB slab allocator (try 2)
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References: <20090123154653.GA14517@wotan.suse.de> <200902032250.55968.nickpiggin@yahoo.com.au> <20090203120139.GM9840@csn.ul.ie> <200902032307.09025.nickpiggin@yahoo.com.au>
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On Tue, 3 Feb 2009, Nick Piggin wrote:

> > so the max_order is inclusive not exclusive. This will force the order-0
> > allocations I think you are looking for.
>
> Well, but in the case of really bad internal fragmentation in the page,
> SLAB will do order-1 allocations even if it doesn't strictly need to.
> Probably this isn't a huge deal, but I think if we do slub_min_objects=1,
> then SLUB won't care about number of objects per page, and slub_max_order=1
> will mean it stops caring about fragmentation after order-1. I think. Which
> would be pretty close to SLAB (depending on exactly how much fragmentation
> it cares about).

slub_max_order=0 will fore all possible slabs to order 0. This means that
some slabs that SLAB will run as order 1 will be order 0 under SLUB.