linux-kernel - Re: 2.6.24-rc2: Network commit causes SLUB performance regression with tbench

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Message-ID: <Pine.LNX.4.64.0711141650150.21965@schroedinger.engr.sgi.com>
Date:	Wed, 14 Nov 2007 17:03:25 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	David Miller <davem@...emloft.net>
cc:	herbert@...dor.apana.org.au, nickpiggin@...oo.com.au,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: 2.6.24-rc2: Network commit causes SLUB performance regression
 with tbench

On Wed, 14 Nov 2007, David Miller wrote:

> > As a result, we may allocate more than a page of data in the
> > non-TSO case when exactly one page is desired.

Well this is likely the result of the SLUB regression. If you allocate an 
order 1 page then the zone locks need to be taken. SLAB queues the a 
couple of higher order pages and can so serve a couple of requests without 
going into the page allocator whereas SLUB has to go directly to the page 
allocator for allocate and free. I guess that needs fixing in the page 
allocator. Or do I need to add a mechanism to buffer higher order page 
allcoations to SLUB?

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