Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761971AbXE2G3H (ORCPT ); Tue, 29 May 2007 02:29:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752235AbXE2G24 (ORCPT ); Tue, 29 May 2007 02:28:56 -0400 Received: from nz-out-0506.google.com ([64.233.162.226]:26357 "EHLO nz-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751113AbXE2G2z (ORCPT ); Tue, 29 May 2007 02:28:55 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=AcK3LDF8SBRV4zlO4vNIKOZ8T3ApplOXWEGRdjHo6NyfgAwGfNg4J7C4FDbGCqZWfu77wWKNE1kV2slY1MjSdOlCC6xLPAPW5a24Ulle6rl0qeybclmseTXAcVsFdpwUoMKGDDdx/G5oKBwu741Y5KvmgFWP3Gt5UzIu3I3Zn44= Message-ID: Date: Tue, 29 May 2007 11:58:54 +0530 From: "Satyam Sharma" To: "Bill Davidsen" Subject: Re: What causes iowait other than waiting for i/o? Cc: "Linux Kernel mailing List" In-Reply-To: <465B4B75.2040602@tmr.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <465B4B75.2040602@tmr.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1296 Lines: 27 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 ... Satyam - 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/