From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755886Ab2LGJ7E (ORCPT ); Fri, 7 Dec 2012 04:59:04 -0500 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:60803 "EHLO e06smtp12.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755795Ab2LGJ7C (ORCPT ); Fri, 7 Dec 2012 04:59:02 -0500 Date: Fri, 7 Dec 2012 11:00:07 +0100 From: Heiko Carstens To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, alan@lxorguk.ukuu.org.uk, Martin Schwidefsky , CAI Qian Subject: Re: [ 20/27] s390/mm: have 16 byte aligned struct pages Message-ID: <20121207100007.GB5129@osiris.de.ibm.com> References: <20121207005825.232489605@linuxfoundation.org> <20121207005831.786407731@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121207005831.786407731@linuxfoundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) x-cbid: 12120709-8372-0000-0000-0000048E218B Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 06, 2012 at 04:59:04PM -0800, Greg Kroah-Hartman wrote: > 3.6-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Heiko Carstens > > commit 4bffbb3455372a26816e364fb4448810f7014452 upstream. > > Select HAVE_ALIGNED_STRUCT_PAGE on s390, so that the slub allocator can make > use of compare and swap double for lockless updates. This increases the size > of struct page to 64 bytes (instead of 56 bytes), however the performance gain > justifies the increased size: > > - now excactly four struct pages fit into a single cache line; the > case that accessing a struct page causes two cache line loads > does not exist anymore. > - calculating the offset of a struct page within the memmap array > is only a simple shift instead of a more expensive multiplication. > > A "hackbench 200 process 200" run on a 32 cpu system did show an 8% runtime > improvement. > > Signed-off-by: Heiko Carstens > Signed-off-by: Martin Schwidefsky > Signed-off-by: CAI Qian > Signed-off-by: Greg Kroah-Hartman Same as for 3.4: compare and swap double is not available for 3.6 on s390.