From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Mackall Subject: Re: [regression] nf_iterate(), BUG: unable to handle kernel NULL pointer dereference Date: Thu, 24 Jul 2008 14:21:49 -0500 Message-ID: <1216927309.15519.253.camel@calx> References: <20080724060448.GA10203@elte.hu> <200807242256.09107.nickpiggin@yahoo.com.au> <20080724130422.GB7426@gondor.apana.org.au> <200807242313.47041.nickpiggin@yahoo.com.au> <1216906342.12021.0.camel@penberg-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Nick Piggin , Herbert Xu , Patrick McHardy , Ingo Molnar , David Miller , w@1wt.eu, davidn@davidnewall.com, torvalds@linux-foundation.org, akpm@linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stefanr@s5r6.in-berlin.de, rjw@sisk.pl, ilpo.jarvinen@helsinki.fi, Dave Jones , Christoph Lameter To: Pekka Enberg Return-path: Received: from waste.org ([66.93.16.53]:49674 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754830AbYGXT0H (ORCPT ); Thu, 24 Jul 2008 15:26:07 -0400 In-Reply-To: <1216906342.12021.0.camel@penberg-laptop> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2008-07-24 at 16:32 +0300, Pekka Enberg wrote: > On Thu, Jul 24, 2008 at 10:56:08PM +1000, Nick Piggin wrote: > > > > OTOH, skb allocation uses kmalloc don't they? So you could stil= l use > > > > SLOB ksize for that I guess. >=20 > On Thursday 24 July 2008 23:04, Herbert Xu wrote: > > > Yes I was referring to the data portion which is kmalloc'ed. > > > That is also why I'm interested in ksize because a priori we > > > don't know exactly how big it's going to be. However, we do > > > know that statistically 1500 will dominate. > > > > > > I'm not interested in ksize for kmem_cache at all. So in fact > > > we could have something simpler that's based on kmalloc's roundin= g > > > algorithm instead. >=20 > =EF=BB=BFOn Thu, 2008-07-24 at 23:13 +1000, Nick Piggin wrote: > > Yes you could definitely have a function that returns allocated > > bytes for a given kmalloc size. Should be about as fast or faster > > than extracting the size from the kaddr... >=20 > Yup, makes sense. On the other hand, I can imagine useful allocator changes where this would not be a constant of requested size. For instance, imagine we had a classless bucket allocator, but with a heuristic to try a larger bucket when it wasn't cheap/possible to allocate a right-sized object (because of memory pressure, etc.) and larger ones were available. This sort of thing is a pretty small change for SLAB/SLUB. --=20 Mathematics is the supreme nostalgia of our time.