From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757530AbZEVKIt (ORCPT ); Fri, 22 May 2009 06:08:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757240AbZEVKIV (ORCPT ); Fri, 22 May 2009 06:08:21 -0400 Received: from bilbo.ozlabs.org ([203.10.76.25]:39523 "EHLO bilbo.ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757285AbZEVKIU (ORCPT ); Fri, 22 May 2009 06:08:20 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <18966.31089.52074.614650@cargo.ozlabs.ibm.com> Date: Fri, 22 May 2009 20:07:45 +1000 From: Paul Mackerras To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Corey Ashford , Thomas Gleixner Subject: Re: [PATCH 2/2] perf_counter: optimize context switch between identical inherited contexts In-Reply-To: <1242985332.26820.630.camel@twins> References: <18966.10075.781053.231153@cargo.ozlabs.ibm.com> <18966.10666.517218.332164@cargo.ozlabs.ibm.com> <1242984129.26820.627.camel@twins> <1242985332.26820.630.camel@twins> X-Mailer: VM 8.0.12 under 22.2.1 (i486-pc-linux-gnu) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > Ah, should I read this as 'n' lmbench instances on a single cpu? So that > we get multiple inheritance sets mixed and have to switch between them? No, it's one lat_ctx instance, which creates N processes connected in a ring with pipes, and passes a token around some number of times and measures the overall time to do that. It subtracts off the time it takes to do all the pipe reads and writes in a single process to get an estimate of how much the context switches are costing. Paul.