From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757946AbXK0J6A (ORCPT ); Tue, 27 Nov 2007 04:58:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753671AbXK0J5x (ORCPT ); Tue, 27 Nov 2007 04:57:53 -0500 Received: from ozlabs.org ([203.10.76.45]:38860 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753480AbXK0J5w (ORCPT ); Tue, 27 Nov 2007 04:57:52 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <18251.59930.30260.145217@cargo.ozlabs.ibm.com> Date: Tue, 27 Nov 2007 20:57:46 +1100 From: Paul Mackerras To: Johannes Berg Cc: Linux Kernel list , linuxppc-dev list Subject: Re: time accounting problem (powerpc only?) In-Reply-To: <1196094193.4149.287.camel@johannes.berg> References: <1195814816.4149.94.camel@johannes.berg> <1196094193.4149.287.camel@johannes.berg> X-Mailer: VM 7.19 under Emacs 21.4.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Johannes Berg writes: > Contrary to what I claimed later in the thread, my 64-bit powerpc box > (quad-core G5) doesn't suffer from this problem. > > Does anybody have any idea? I don't even know how to debug it further. I see it on my G4 powerbook. However, a compute-bound task runs just as fast (i.e. completes in the same elapsed time) as on older kernels, so it does look like it is just an accounting problem. If the CPU was really spending more than half its time servicing hardware interrupts, the task should take more than twice as long to complete. Paul.