Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934032Ab0KPIzF (ORCPT ); Tue, 16 Nov 2010 03:55:05 -0500 Received: from mtagate1.de.ibm.com ([195.212.17.161]:49064 "EHLO mtagate1.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932425Ab0KPIzD (ORCPT ); Tue, 16 Nov 2010 03:55:03 -0500 Date: Tue, 16 Nov 2010 09:54:56 +0100 From: Martin Schwidefsky To: Peter Zijlstra Cc: Oleg Nesterov , Michael Holzheu , Shailabh Nagar , Andrew Morton , Venkatesh Pallipadi , Suresh Siddha , Ingo Molnar , John stultz , Thomas Gleixner , Balbir Singh , Heiko Carstens , Roland McGrath , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [RFC][PATCH v2 5/7] taskstats: Improve cumulative CPU time accounting Message-ID: <20101116095456.7389bebc@mschwide.boeblingen.de.ibm.com> In-Reply-To: <1289844606.2109.526.camel@laptop> References: <20101111170352.732381138@linux.vnet.ibm.com> <20101111170815.404670062@linux.vnet.ibm.com> <20101113183810.GA9021@redhat.com> <20101115165521.21baac60@mschwide.boeblingen.de.ibm.com> <1289837036.2109.501.camel@laptop> <20101115184910.549a828b@mschwide.boeblingen.de.ibm.com> <1289843517.2109.521.camel@laptop> <20101115190031.5a50e760@mschwide.boeblingen.de.ibm.com> <1289844606.2109.526.camel@laptop> Organization: IBM Corporation X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1634 Lines: 42 On Mon, 15 Nov 2010 19:10:06 +0100 Peter Zijlstra wrote: > On Mon, 2010-11-15 at 19:00 +0100, Martin Schwidefsky wrote: > > On Mon, 15 Nov 2010 18:51:57 +0100 > > Peter Zijlstra wrote: > > > > > On Mon, 2010-11-15 at 18:49 +0100, Martin Schwidefsky wrote: > > > > > To what purpose? > > > > > > > > Is that a trick question? Why do we have tools like "top"? Or process > > > > accounting? The point is that the quality of the numbers we get right > > > > now is rather bad, the overhead of scanning /proc is horrendous and > > > > the 10ms granularity is rather coarse. > > > > > > But you're not just replacing top, you're adding all kinds of new > > > accounting crap all over the place. > > > > We DO replace top. Patch #7 of 7. > > You _also_ replace top, but its not by far the only thing you do. If you > simply replaced top you wouldn't need to add tons of extra accounting, > would you? There are basically two things we want to accomplish: 1) Make top faster by replacing the /proc based data gathering with taskstats. To really make it go fast with taskstats we filter with last_depart to read only tasks that have changed since the last snapshot. 2) Make top more precise. That is where all of the extra accounting comes into play. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/