linux-kernel - Re: [patch] SLQB slab allocator (try 2)

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Message-ID: <20090203120139.GM9840@csn.ul.ie>
Date:	Tue, 3 Feb 2009 12:01:39 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Nick Piggin <npiggin@...e.de>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lin Ming <ming.m.lin@...el.com>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [patch] SLQB slab allocator (try 2)

On Tue, Feb 03, 2009 at 10:50:54PM +1100, Nick Piggin wrote:
> On Tuesday 03 February 2009 22:28:52 Mel Gorman wrote:
> > On Tue, Feb 03, 2009 at 09:36:24PM +1100, Nick Piggin wrote:
> 
> > > I'd be interested to see how slub performs if booted with
> > > slub_min_objects=1 (which should give similar order pages to SLAB and
> > > SLQB).
> >
> > Just to clarify on this last point, do you mean slub_max_order=0 to
> > force order-0 allocations in SLUB?
> 
> Hmm... I think slub_min_objects=1 should also do basically the same.
> Actually slub_min_object=1 and slub_max_order=1 should get closest I
> think.
> 

I'm going with slub_min_objects=1 and slub_max_order=0. A quick glance
of the source shows the calculation as

        for (order = max(min_order,
                                fls(min_objects * size - 1) - PAGE_SHIFT);
                        order <= max_order; order++) {

so the max_order is inclusive not exclusive. This will force the order-0
allocations I think you are looking for.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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