From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760021AbXEYJnt (ORCPT ); Fri, 25 May 2007 05:43:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751171AbXEYJnm (ORCPT ); Fri, 25 May 2007 05:43:42 -0400 Received: from caramon.arm.linux.org.uk ([217.147.92.249]:4670 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750941AbXEYJnm (ORCPT ); Fri, 25 May 2007 05:43:42 -0400 Date: Fri, 25 May 2007 10:43:24 +0100 From: Russell King To: "Yu, Fenghua" Cc: Andrew Morton , Ravikiran G Thirumalai , "Siddha, Suresh B" , clameter@sgi.com, linux-kernel@vger.kernel.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com Subject: Re: [PATCH 1/2] Define new percpu interface for shared data -- version 3 Message-ID: <20070525094323.GB20090@flint.arm.linux.org.uk> Mail-Followup-To: "Yu, Fenghua" , Andrew Morton , Ravikiran G Thirumalai , "Siddha, Suresh B" , clameter@sgi.com, linux-kernel@vger.kernel.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com References: <20070523123153.c4f8c7e6.akpm@linux-foundation.org> <79E93560F4A5FD42BB769DAAF8BEF62A01AA8E7C@scsmsx411.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <79E93560F4A5FD42BB769DAAF8BEF62A01AA8E7C@scsmsx411.amr.corp.intel.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 23, 2007 at 02:13:24PM -0700, Yu, Fenghua wrote: > Yes, in theory, sharing shared percpu data with local percpu data in one > cache line can cause cache line contention between remote and local > access. What's "shared percpu data" ? It sounds to me like a contradiction in terms. Isn't percpu data supposed to only be accessed by the CPU which owns it to prevent cache line bouncing? In which case, what's the point of sharing that data with other CPUs? Surely "shared percpu data" is just the same as normal data? -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: