From: Matt Mackall Subject: Re: [PATCH] Export symbol ksize() Date: Sun, 15 Feb 2009 19:28:46 -0600 Message-ID: <1234747726.5669.215.camel@calx> References: <20090212104349.GA13859@gondor.apana.org.au> <1234435521.28812.165.camel@penberg-laptop> <20090212105034.GC13859@gondor.apana.org.au> <1234454104.28812.175.camel@penberg-laptop> <20090215133638.5ef517ac.akpm@linux-foundation.org> <1234734194.5669.176.camel@calx> <20090215135555.688ae1a3.akpm@linux-foundation.org> <1234741781.5669.204.camel@calx> <20090215170052.44ee8fd5.akpm@linux-foundation.org> <20090216012110.GA13575@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Andrew Morton , Pekka Enberg , "Kirill A. Shutemov" , Christoph Lameter , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-crypto@vger.kernel.org, Geert.Uytterhoeven@sonycom.com To: Herbert Xu Return-path: Received: from waste.org ([66.93.16.53]:50176 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756099AbZBPB3Y (ORCPT ); Sun, 15 Feb 2009 20:29:24 -0500 In-Reply-To: <20090216012110.GA13575@gondor.apana.org.au> Sender: linux-crypto-owner@vger.kernel.org List-ID: 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