linux-kernel - Re: No, really, stop trying to delete slab until you've finished making slub perform as well

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Date:	Mon, 4 Aug 2008 15:48:23 +0100
From:	Jamie Lokier <jamie@...reable.org>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Matthew Wilcox <matthew@....cx>,
	Pekka Enberg <penberg@...helsinki.fi>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, Mel Gorman <mel@...net.ie>,
	andi@...stfloor.org, Rik van Riel <riel@...hat.com>
Subject: Re: No, really, stop trying to delete slab until you've finished making slub perform as well

Christoph Lameter wrote:
> Matthew Wilcox wrote:
> > On Fri, May 09, 2008 at 07:21:01PM -0700, Christoph Lameter wrote:
> >> - Add a patch that obsoletes SLAB and explains why SLOB does not support
> >>   defrag (Either of those could be theoretically equipped to support
> >>   slab defrag in some way but it seems that Andrew/Linus want to reduce
> >>   the number of slab allocators).
> > 
> > Do we have to once again explain that slab still outperforms slub on at
> > least one important benchmark?  I hope Nick Piggin finds time to finish
> > tuning slqb; it already outperforms slub.
> > 
> 
> Uhh. I forgot to delete that statement. I did not include the patch
> in the series.
> 
> We have a fundamental issue design issue there. Queuing on free can result in
> better performance as in SLAB. However, it limits concurrency (per node lock
> taking) and causes latency spikes due to queue processing (f.e. one test load
> had 118.65 vs. 34 usecs just by switching to SLUB).

Vaguely on this topic, has anyone studied the effects of SLAB/SLUB
etc. on MMUless systems?

-- Jamie
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