From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763261AbXKTCVO (ORCPT ); Mon, 19 Nov 2007 21:21:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760377AbXKTCUS (ORCPT ); Mon, 19 Nov 2007 21:20:18 -0500 Received: from terminus.zytor.com ([198.137.202.10]:48885 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756291AbXKTCUP (ORCPT ); Mon, 19 Nov 2007 21:20:15 -0500 Message-ID: <47424435.8050704@zytor.com> Date: Mon, 19 Nov 2007 18:19:33 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: David Miller CC: clameter@sgi.com, ak@suse.de, akpm@linux-foundation.org, travis@sgi.com, mathieu.desnoyers@polymtl.ca, linux-kernel@vger.kernel.org Subject: Re: [rfc 37/45] x86_64: Support for fast per cpu operations References: <20071120011132.143632442@sgi.com> <20071120011340.569486037@sgi.com> <47423FB7.20800@zytor.com> <20071119.181720.03409715.davem@davemloft.net> In-Reply-To: <20071119.181720.03409715.davem@davemloft.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org David Miller wrote: >> There was, at some point, discussion about using the gcc TLS mechanism, >> which should permit even better code to be generated. Unfortunately, it >> would require gcc to be able to reference %gs instead of %fs (and vice >> versa for i386), which I don't think is available in anything except >> maybe the most cutting-edge version of gcc. > > You can't use __thread because GCC will cache __thread computed > addresses across context switches and cpu changes. > > It's been tried before on powerpc, it doesn't work. OK, that pretty much answers that question. -hpa