From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761344AbYGOPr6 (ORCPT ); Tue, 15 Jul 2008 11:47:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758208AbYGOPrM (ORCPT ); Tue, 15 Jul 2008 11:47:12 -0400 Received: from gw.goop.org ([64.81.55.164]:43642 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758146AbYGOPrL (ORCPT ); Tue, 15 Jul 2008 11:47:11 -0400 Message-ID: <487CC671.3000501@goop.org> Date: Tue, 15 Jul 2008 08:46:57 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Linus Torvalds CC: Ingo Molnar , linux-kernel@vger.kernel.org, Peter Zijlstra , Thomas Gleixner , Andrew Morton , Mike Travis Subject: Re: [git pull] core/percpu for v2.6.27 References: <20080714143413.GA19134@elte.hu> In-Reply-To: X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus Torvalds wrote: > Can you explain what this does and who needs it? The percpu_xchg() looks > particularly pointless, since it's always a locked SMP-safe instruction on > x86, so a nonpreemptible load+store will likely be much faster. The essence of those changes is to work towards unifying the i386 and x86-64 percpu mechanisms. But I wasn't terribly convinced by some of the frills around the edges, like the xchg operation. The work is being driven by Mike Travis and the huge numa people, so perhaps they have a use for it. J