Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759646AbXE2Q5W (ORCPT ); Tue, 29 May 2007 12:57:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751790AbXE2Q5P (ORCPT ); Tue, 29 May 2007 12:57:15 -0400 Received: from mx1.redhat.com ([66.187.233.31]:43972 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751180AbXE2Q5P (ORCPT ); Tue, 29 May 2007 12:57:15 -0400 Message-ID: <465C5B61.6000702@redhat.com> Date: Tue, 29 May 2007 12:57:05 -0400 From: Rik van Riel Organization: Red Hat, Inc User-Agent: Thunderbird 1.5.0.7 (X11/20061008) MIME-Version: 1.0 To: Bill Davidsen CC: Linux Kernel mailing List Subject: Re: What causes iowait other than waiting for i/o? References: <465B4B75.2040602@tmr.com> In-Reply-To: <465B4B75.2040602@tmr.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1239 Lines: 27 Bill Davidsen wrote: > I recently noted that my system was spending a lot of time in i/o wait > when doing some tasks which I thought didn't involve i/o, as noted by > the lack of disk light activity most of the time. I thought of network, > certainly the NIC had no activity for this job. So I set up a little > loop to capture all disk i/o and network activity (including loopback). > That was no obvious help, and the program doesn't use pipes. > > At this point I'm really curious, does someone have a good clue? > > Note: I don't think this is a bug or performance issue, unless the > kernel is doing something and charging time to iowait instead of system > I don't see anything to fix, but I would like to understand. All filesystem IO and direct disk IO can cause iowait. This includes NFS activity. -- Politics is the struggle between those who want to make their country the best in the world, and those who believe it already is. Each group calls the other unpatriotic. - 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/