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

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Date:	Tue, 3 Feb 2009 11:28:52 +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 09:36:24PM +1100, Nick Piggin wrote:
> On Tuesday 03 February 2009 21:12:06 Mel Gorman wrote:
> > On Mon, Jan 26, 2009 at 10:48:26AM +0200, Pekka Enberg wrote:
> > > Hi Nick,
> > >
> > > On Fri, 2009-01-23 at 16:46 +0100, Nick Piggin wrote:
> > > > Since last time, fixed bugs pointed out by Hugh and Andi, cleaned up
> > > > the code suggested by Ingo (haven't yet incorporated Ingo's last
> > > > patch).
> > > >
> > > > Should have fixed the crash reported by Yanmin (I was able to reproduce
> > > > it on an ia64 system and fix it).
> > > >
> > > > Significantly reduced static footprint of init arrays, thanks to Andi's
> > > > suggestion.
> > > >
> > > > Please consider for trial merge for linux-next.
> > >
> > > I merged a the one you resent privately as this one didn't apply at all.
> > > The code is in topic/slqb/core branch of slab.git and should appear in
> > > linux-next tomorrow.
> > >
> > > Testing and especially performance testing is welcome. If any of the HPC
> > > people are reading this, please do give SLQB a good beating as Nick's
> > > plan is to replace both, SLAB and SLUB, with it in the long run.As
> > > Christoph has expressed concerns over latency issues of SLQB, I suppose
> > > it would be interesting to hear if it makes any difference to the
> > > real-time folks.
> >
> > The HPC folks care about a few different workloads but speccpu is one that
> > shows up. I was in the position to run tests because I had put together
> > the test harness for a paper I spent the last month writing. This mail
> > shows a comparison between slab, slub and slqb for speccpu2006 running a
> > single thread and sysbench ranging clients from 1 to 4*num_online_cpus()
> > (16 in both cases). Additional tests were not run because just these two
> > take one day per kernel to complete. Results are ratios to the SLAB figures
> > and based on an x86-64 and ppc64 machine.
> 
> Hi Mel,
> 
> This is very nice, thanks for testing. SLQB and SLUB are quite similar
> in a lot of cases, which indeed could be explained by cacheline placement
> (both of these can allocate down to much smaller sizes, and both of them
> also put metadata directly in free object memory rather than external
> locations).
> 
> But it will be interesting to try looking at some of the tests where
> SLQB has larger regressions, so that might give me something to go on
> if I can lay my hands on speccpu2006...
> 
> 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?


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