From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 13 May 2002 07:46:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 13 May 2002 07:46:11 -0400 Received: from inje.iskon.hr ([213.191.128.16]:55224 "EHLO inje.iskon.hr") by vger.kernel.org with ESMTP id ; Mon, 13 May 2002 07:46:05 -0400 To: Rik van Riel Cc: Bill Davidsen , , Subject: Re: [RFC][PATCH] IO wait accounting In-Reply-To: Reply-To: zlatko.calusic@iskon.hr X-Face: s71Vs\G4I3mB$X2=P4h[aszUL\%"`1!YRYl[JGlC57kU-`kxADX}T/Bq)Q9.$fGh7lFNb.s i&L3xVb:q_Pr}>Eo(@kU,c:3:64cR]m@27>1tGl1):#(bs*Ip0c}N{:JGcgOXd9H'Nwm:}jLr\FZtZ pri/C@\,4lW<|jrq^<):Nk%Hp@G&F"r+n1@BoH From: Zlatko Calusic Date: Mon, 13 May 2002 13:45:54 +0200 Message-ID: User-Agent: Gnus/5.090005 (Oort Gnus v0.05) XEmacs/21.4 (Common Lisp, i386-debian-linux) 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 Rik van Riel writes: > On Sun, 12 May 2002, Zlatko Calusic wrote: >> Rik van Riel writes: >> > >> > And should we measure read() waits as well as page faults or >> > just page faults ? >> >> Definitely both. > > OK, I'll look at a way to implement these stats so that > every IO wait counts as iowait time ... preferably in a > way that doesn't touch the code in too many places ;) > >> Somewhere on the web was a nice document explaining >> how Solaris measures iowait%, I read it few years ago and it was a >> great stuff (quite nice explanation). >> >> I'll try to find it, as it could be helpful. > > Please, it would be useful to get our info compatible with > theirs so sysadmins can read their statistics the same on > both systems. > Yes, that would be nice. Anyway, finding the document I mentioned will be much harder than I thought. Googling last 15 minutes didn't make progress. But, I'll keep trying. Anyway, here is how Aix defines it: Average percentage of CPU time that the CPUs were idle during which the system had an outstanding disk I/O request. This value may be inflated if the actual number of I/O requesting threads is less than the number of idling processors. (http://support.bull.de/download/redbooks/Performance/OptimizingYourSystemPerformance.pdf) Also, Sun has a nice collection of articles at http://www.sun.com/sun-on-net/itworld/, and among them http://www.sun.com/sun-on-net/itworld/UIR981001perf.html which speaks about wait time, but I'm still searching for a more technical document... -- Zlatko