From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264413AbTDPOrQ (for ); Wed, 16 Apr 2003 10:47:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264415AbTDPOrQ (for ); Wed, 16 Apr 2003 10:47:16 -0400 Received: from zero.aec.at ([193.170.194.10]:54020 "EHLO zero.aec.at") by vger.kernel.org with ESMTP id S264413AbTDPOrP (for ); Wed, 16 Apr 2003 10:47:15 -0400 Date: Wed, 16 Apr 2003 16:58:53 +0200 From: Andi Kleen To: "David S. Miller" Cc: ak@muc.de, akpm@digeo.com, linux-kernel@vger.kernel.org, anton@samba.org, schwidefsky@de.ibm.com, davidm@hpl.hp.com, matthew@wil.cx, ralf@linux-mips.org, rth@redhat.com Subject: Re: Reduce struct page by 8 bytes on 64bit Message-ID: <20030416145853.GA2421@averell> References: <20030416140715.GA2159@averell> <20030416.072638.65480350.davem@redhat.com> <20030416144312.GA2327@averell> <20030416.073814.124147956.davem@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030416.073814.124147956.davem@redhat.com> User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 16, 2003 at 04:38:14PM +0200, David S. Miller wrote: > From: Andi Kleen > Date: Wed, 16 Apr 2003 16:43:12 +0200 > > On sparc64. But is that true too for all other 64bit architectures supported? > > e.g. How about PA-RISC? (always seems to do things differently) > > It cannot require more than the existing API requires, which is > "unsigned long *bitmask", ie. anything equivalent in behavior to an > unsigned long pointer is good enough. Sure, but perhaps it does assume all accesses to this bitmap are going through the set_bit functions. e.g. consider an implementation that uses a spinlock for this - parisc seems to do that for example from a quick look into their bitops.h. And they have an 64bit kernel too. In this case part of the unsigned long could be accessed directly using the aliasing. -Andi