linux-kernel - Re: [RFC/PATCH 2/3] SLUB: make ksize() more strict for page allocator pass-through

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Message-ID: <Pine.LNX.4.64.0805211412340.17915@schroedinger.engr.sgi.com>
Date:	Wed, 21 May 2008 14:14:45 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	linux-kernel@...r.kernel.org, mpm@...enic.com, lethal@...ux-sh.org,
	dhowells@...hat.com
Subject: Re: [RFC/PATCH 2/3] SLUB: make ksize() more strict for page allocator
 pass-through

On Wed, 21 May 2008, Pekka Enberg wrote:

> Christoph Lameter wrote:
> > Why is it too big? Without your additions it is converting kmallocs inline
> > to get_free_pages(). That results in a simple function call with two
> > constant parameters.
> 
> Well, it's a PITA because of #include dependencies in any case. Is moving it
> out-of-line a problem?
> 
> Christoph Lameter wrote:
> > The patch touches the page struct uselessly. I think the PageSlab marking is
> > useful for debugging but not for a production kernel.
> 
> Hmm, where? page_address() already references ->virtual. I suppose
> CONFIG_SLUB_DEBUG is a no no as well then so do we want to add a
> CONFIG_KSIZE_DEBUG config option...? (Btw, I removed the BUG_ON() from kfree()
> as spotted by Vegard Nossum.)

If it has to be then add CONFIG_KSIZE_DEBUG. There are a number of 
debugging techniques (kmem_check?) that should not be compiled in. Maybe 
add a new config option for those. CONFIG_SLUB_ENABLE_EXPENSIVE_DEBUG?

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