Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761093AbXE2N2k (ORCPT ); Tue, 29 May 2007 09:28:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762675AbXE2N0j (ORCPT ); Tue, 29 May 2007 09:26:39 -0400 Received: from mail.tmr.com ([64.65.253.246]:33344 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762734AbXE2N0i (ORCPT ); Tue, 29 May 2007 09:26:38 -0400 Message-ID: <465C2A11.5070208@tmr.com> Date: Tue, 29 May 2007 09:26:41 -0400 From: Bill Davidsen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061105 SeaMonkey/1.0.6 MIME-Version: 1.0 To: Satyam Sharma CC: Linux Kernel mailing List Subject: Re: What causes iowait other than waiting for i/o? References: <465B4B75.2040602@tmr.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1784 Lines: 37 Satyam Sharma wrote: > Hi Bill, > > On 5/29/07, 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. > > What tool / kernel instrumentation / mechanism are you using to > determine that some task(s) are indeed blocked waiting for i/o? Perhaps > some userspace process accounting tools could be "broken" in the sense > that they generalize all uninterruptible sleep as waiting for i/o ... I wouldn't expect /proc/stat and similar to be broken in that way, but If no one has a better idea I guess I will assume there's a check needed of where time is added to iowait. I was hoping to avoid a full kernel search. Never thought of /proc data as a user space tool, but I guess. -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot - 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/