linux-kernel - Re: [PATCH] Export symbol ksize()

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Message-Id: <20090215133638.5ef517ac.akpm@linux-foundation.org>
Date:	Sun, 15 Feb 2009 13:36:38 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Matt Mackall <mpm@...enic.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-crypto@...r.kernel.org,
	Geert.Uytterhoeven@...ycom.com
Subject: Re: [PATCH] Export symbol ksize()

On Thu, 12 Feb 2009 17:55:04 +0200 Pekka Enberg <penberg@...helsinki.fi> wrote:

> On Thu, Feb 12, 2009 at 12:45:21PM +0200, Pekka Enberg wrote:
> > > 
> > > Because the API was being widely abused in the nommu code, for example.
> > > I'd rather not add it back for this special case which can be handled
> > > otherwise.
> 
> On Thu, 2009-02-12 at 18:50 +0800, Herbert Xu wrote:
> > I'm sorry but that's like banning the use of heaters just because
> > they can abused and cause fires.
> > 
> > I think I've said this to you before but in networking we very much
> > want to use ksize because the standard case of a 1500-byte packet
> > has loads of extra room given by kmalloc which all goes to waste
> > right now.
> > 
> > If we could use ksize then we can stuff loads of metadata in that
> > space.
> 
> OK, fair enough, I applied Kirill's patch. Thanks.
> 

Could we please have more details regarding this:

> The ksize() function is not exported to modules because it has non-standard
> behavour across different slab allocators. 

How does the behaviour differ?  It this documented?  Can we fix it?
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