From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753455Ab1G3Gdf (ORCPT ); Sat, 30 Jul 2011 02:33:35 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:43809 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753417Ab1G3Gde (ORCPT ); Sat, 30 Jul 2011 02:33:34 -0400 Subject: Re: [GIT PULL] Lockless SLUB slowpaths for v3.1-rc1 From: Eric Dumazet To: Andi Kleen Cc: Christoph Lameter , Pekka Enberg , torvalds@linux-foundation.org, akpm@linux-foundation.org, rientjes@google.com, hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Date: Sat, 30 Jul 2011 08:33:28 +0200 Message-ID: <1312007608.2873.77.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le vendredi 29 juillet 2011 à 16:18 -0700, Andi Kleen a écrit : > Christoph Lameter writes: > > > On Fri, 29 Jul 2011, Pekka Enberg wrote: > > > >> We haven't come up with a solution to keep struct page size the same but I > >> think it's a reasonable trade-off. > > > > The change requires the page struct to be aligned to a double word > > boundary. > > Why is that? > Because cmpxchg16b is believed to require a 16bytes alignment. http://siyobik.info/main/reference/instruction/CMPXCHG8B%2FCMPXCHG16B 64-Bit Mode Exceptions ... #GP(0) If the memory address is in a non-canonical form. If memory operand for CMPXCHG16B is not aligned on a 16-byte boundary. If CPUID.01H:ECX.CMPXCHG16B[bit 13] = 0.