From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264278AbUBHXDV (ORCPT ); Sun, 8 Feb 2004 18:03:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264364AbUBHXDV (ORCPT ); Sun, 8 Feb 2004 18:03:21 -0500 Received: from dp.samba.org ([66.70.73.150]:23972 "EHLO lists.samba.org") by vger.kernel.org with ESMTP id S264278AbUBHXDS (ORCPT ); Sun, 8 Feb 2004 18:03:18 -0500 From: Rusty Russell To: David Woodhouse Cc: linux-kernel@vger.kernel.org, matthew@wil.cx, davem@redhat.com Subject: Re: When should we use likely() / unlikely() / get_unaligned() ? In-reply-to: Your message of "Sun, 08 Feb 2004 11:13:53 -0000." <1076238833.12587.229.camel@imladris.demon.co.uk> Date: Mon, 09 Feb 2004 10:00:47 +1100 Message-Id: <20040208230331.79FEB2C003@lists.samba.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org In message <1076238833.12587.229.camel@imladris.demon.co.uk> you write: > To be honest, I'm more interested in the case of get_unaligned(). The > principle is fairly similar -- the ratio between the performance of the > inline and the exception cases varies wildly from architecture to > architecture. But the range is far wider -- we now support architectures > in 2.6 where alignment fixups _cannot_ happen, and the cost of the > 'exception' case should be considered infinite. Um, we do? I thought it was compulsory in the kernel, otherwise networking breaks on packets w/ wierd hardware headers. Rusty. -- Anyone who quotes me in their sig is an idiot. -- Rusty Russell.