From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757911AbXKTDde (ORCPT ); Mon, 19 Nov 2007 22:33:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752596AbXKTDd1 (ORCPT ); Mon, 19 Nov 2007 22:33:27 -0500 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:43347 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751484AbXKTDd0 (ORCPT ); Mon, 19 Nov 2007 22:33:26 -0500 Date: Mon, 19 Nov 2007 19:33:25 -0800 (PST) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Andi Kleen cc: David Miller , akpm@linux-foundation.org, travis@sgi.com, mathieu.desnoyers@polymtl.ca, linux-kernel@vger.kernel.org Subject: Re: [rfc 00/45] [RFC] CPU ops and a rework of per cpu data handling on x86_64 In-Reply-To: <200711200425.34849.ak@suse.de> Message-ID: References: <20071120011132.143632442@sgi.com> <20071119.175116.55102316.davem@davemloft.net> <200711200425.34849.ak@suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org n Tue, 20 Nov 2007, Andi Kleen wrote: > > > Although we have a per-cpu area base in a fixed global register > > for addressing, the above isn't beneficial on sparc64 because > > the atomic is much slower than doing a: > > > > local_irq_disable(); > > nonatomic_percpu_memory_op(); > > local_irq_enable(); > > Again might be pointing out the obvious, but you > need of course save_flags()/restore_flags(), not disable/enable(). > > If it was just disable/enable x86 could do it much faster too > and Christoph probably would never felt the need to approach > this project for his SLUB fast path. I already have no need for that anymore with the material now in Andrews tree. However, this cuts out another 6 cycles from the fastpath and I found that the same principles reduce overhead all over the kernel.