From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yh0-f45.google.com (mail-yh0-f45.google.com [209.85.213.45]) by kanga.kvack.org (Postfix) with ESMTP id C5C836B0035 for ; Thu, 12 Dec 2013 12:46:04 -0500 (EST) Received: by mail-yh0-f45.google.com with SMTP id v1so593866yhn.32 for ; Thu, 12 Dec 2013 09:46:04 -0800 (PST) Received: from a9-99.smtp-out.amazonses.com (a9-99.smtp-out.amazonses.com. [54.240.9.99]) by mx.google.com with ESMTP id b6si19488242qak.6.2013.12.12.09.46.03 for ; Thu, 12 Dec 2013 09:46:03 -0800 (PST) Date: Thu, 12 Dec 2013 17:46:02 +0000 From: Christoph Lameter Subject: Re: [RFC][PATCH 2/3] mm: slab: move around slab ->freelist for cmpxchg In-Reply-To: <20131211224025.70B40B9C@viggo.jf.intel.com> Message-ID: <00000142e7ea519d-8906d225-c99c-44b5-b381-b573c75fd097-000000@email.amazonses.com> References: <20131211224022.AA8CF0B9@viggo.jf.intel.com> <20131211224025.70B40B9C@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kirill.shutemov@linux.intel.com, Andi Kleen On Wed, 11 Dec 2013, Dave Hansen wrote: > > The write-argument to cmpxchg_double() must be 16-byte aligned. > We used to align 'struct page' itself in order to guarantee this, > but that wastes 8-bytes per page. Instead, we take 8-bytes > internal to the page before page->counters and move freelist > between there and the existing 8-bytes after counters. That way, > no matter how 'stuct page' itself is aligned, we can ensure that > we have a 16-byte area with which to to this cmpxchg. Well this adds additional branching to the fast paths. -- 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/ . Don't email: email@kvack.org