From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta7.messagelabs.com (mail6.bemta7.messagelabs.com [216.82.255.55]) by kanga.kvack.org (Postfix) with ESMTP id 9DE3F900137 for ; Sun, 31 Jul 2011 14:50:52 -0400 (EDT) Received: from wpaz1.hot.corp.google.com (wpaz1.hot.corp.google.com [172.24.198.65]) by smtp-out.google.com with ESMTP id p6VIomTb013993 for ; Sun, 31 Jul 2011 11:50:49 -0700 Received: from pzk5 (pzk5.prod.google.com [10.243.19.133]) by wpaz1.hot.corp.google.com with ESMTP id p6VIofvJ002236 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=NOT) for ; Sun, 31 Jul 2011 11:50:47 -0700 Received: by pzk5 with SMTP id 5so15304172pzk.31 for ; Sun, 31 Jul 2011 11:50:41 -0700 (PDT) Date: Sun, 31 Jul 2011 11:50:39 -0700 (PDT) From: David Rientjes Subject: Re: [GIT PULL] Lockless SLUB slowpaths for v3.1-rc1 In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Pekka Enberg , Linus Torvalds , Andrew Morton , hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Fri, 29 Jul 2011, Christoph Lameter 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. > We won't be coming up with a solution to that since the alignment is a requirement for cmpxchg16b, unfortunately. > The change requires the page struct to be aligned to a double word > boundary. There is actually no variable added to the page struct. Its just > the alignment requirement that causes padding to be added after each page > struct. > Well, the counters variable is added although it doesn't increase the size of the unaligned struct page because of how it is restructured. The end result of the alignment for CONFIG_CMPXCHG_LOCAL is that struct page will increase from 56 bytes to 64 bytes on my config. That's a cost of 128MB on each of my client and server 64GB machines for the netperf benchmark for the ~2.3% speedup. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org