From nobody@FreeBSD.org Tue Jul 14 16:08:09 2009 Return-Path: Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id AFC771065676 for ; Tue, 14 Jul 2009 16:08:09 +0000 (UTC) (envelope-from nobody@FreeBSD.org) Received: from www.freebsd.org (www.freebsd.org [IPv6:2001:4f8:fff6::21]) by mx1.freebsd.org (Postfix) with ESMTP id 9DC1A8FC0C for ; Tue, 14 Jul 2009 16:08:09 +0000 (UTC) (envelope-from nobody@FreeBSD.org) Received: from www.freebsd.org (localhost [127.0.0.1]) by www.freebsd.org (8.14.3/8.14.3) with ESMTP id n6EG89O9006250 for ; Tue, 14 Jul 2009 16:08:09 GMT (envelope-from nobody@www.freebsd.org) Received: (from nobody@localhost) by www.freebsd.org (8.14.3/8.14.3/Submit) id n6EG89l8006249; Tue, 14 Jul 2009 16:08:09 GMT (envelope-from nobody) Message-Id: <200907141608.n6EG89l8006249@www.freebsd.org> Date: Tue, 14 Jul 2009 16:08:09 GMT From: Vladimir Krasovsky To: freebsd-gnats-submit@FreeBSD.org Subject: iostat displays wrong I/O statistics with -c 1 X-Send-Pr-Version: www-3.1 X-GNATS-Notify: >Number: 136759 >Category: bin >Synopsis: iostat(8) displays wrong I/O statistics with -c 1 >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: closed >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Tue Jul 14 16:10:00 UTC 2009 >Closed-Date: Wed Jan 13 20:05:23 UTC 2010 >Last-Modified: Wed Jan 13 20:05:23 UTC 2010 >Originator: Vladimir Krasovsky >Release: 7.0 >Organization: yandex.ru >Environment: FreeBSD host 7.0-STABLE FreeBSD 7.0-STABLE #1: Fri Feb 29 14:05:58 MSK 2008 root@host:/opt/obj/opt/src/sys/W5L_AMD64_ULE amd64 >Description: First line of iostat output always displays arbitrary (and wrong) numbers. user@host:~$ for i in 1 2 3 4; do iostat -c $i -d da2; done da2 KB/t tps MB/s 6.31 64 0.40 da2 KB/t tps MB/s 6.31 64 0.40 12.64 53 0.65 da2 KB/t tps MB/s 6.31 64 0.40 6.67 27 0.18 2.00 23 0.04 da2 KB/t tps MB/s 6.31 64 0.40 2.00 23 0.04 3.27 11 0.04 7.25 16 0.11 As you can see the first line is always the same. Though on different machines at different loads it may differ. >How-To-Repeat: for i in 1 2 3 4; do iostat -c $i -d da2; done >Fix: Use -c 2 or more. >Release-Note: >Audit-Trail: From: Efstratios Karatzas To: bug-followup@freebsd.org, vovets@gmail.com Cc: Subject: Re: bin/136759: iostat(8) displays wrong I/O statistics with -c 1 Date: Wed, 13 Jan 2010 16:40:48 +0200 Hi there, This is definitely not a bug. Take a look at the freebsd man page for iostat(8) http://www.freebsd.org/cgi/man.cgi?query=iostat&apropos=0&sektion=8&manpath=FreeBSD+8.0-RELEASE&format=html The manual clearly states that : "The first statistics that are printed are averaged over the system uptime. To get information about the current activity, a suitable wait time should be specified, so that the subsequent sets of printed statistics will be averaged over that time." So the first line of statistics always contains the "average statistics" since the system started running. If you want to get the statistics for the next 5 secs try something like iostat -c 6 -d some_device Hope this helps -- Efstratios "GPF" Karatzas State-Changed-From-To: open->closed State-Changed-By: gavin State-Changed-When: Wed Jan 13 20:04:48 UTC 2010 State-Changed-Why: As explained by Efstratios Karatzas in the PR trail, this is not a bug. http://www.freebsd.org/cgi/query-pr.cgi?pr=136759 >Unformatted: