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

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Message-ID: <20090216012110.GA13575@gondor.apana.org.au>
Date:	Mon, 16 Feb 2009 09:21:10 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Matt Mackall <mpm@...enic.com>,
	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 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.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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