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

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Message-Id: <1234747726.5669.215.camel@calx>
Date:	Sun, 15 Feb 2009 19:28:46 -0600
From:	Matt Mackall <mpm@...enic.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Christoph Lameter <cl@...ux-foundation.org>,
	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 Mon, 2009-02-16 at 09:21 +0800, Herbert Xu wrote:
> On Sun, Feb 15, 2009 at 05:00:52PM -0800, Andrew Morton wrote:
> >
> > But kmem_cache_size() would tell you how much extra secret memory there
> > is available after the object?
> > 
> > How that gets along with redzoning is a bit of a mystery though.
> > 
> > The whole concept is quite hacky and nasty, isn't it?.  Does
> > networking/crypto actually show any gain from pulling this stunt?
> 
> I see no point in calling ksize on memory that's not kmalloced.
> So no there is nothing to be gained from having kmem_cache_ksize.
> 
> However, for kmalloced memory we're wasting hundreds of bytes
> for the standard 1500 byte allocation without ksize which means
> that we're doing reallocations (and sometimes copying) when it
> isn't necessary.

Yeah. That sucks. We should probably stick in an skb-friendly slab size
and see what happens on network benchmarks.

-- 
http://selenic.com : development and support for Mercurial and Linux


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