amd64/117664: iostat can't display IO current vlaue in first
jhb at FreeBSD.org
Wed Oct 31 16:30:04 PDT 2007
The following reply was made to PR amd64/117664; it has been noted by GNATS.
From: John Baldwin <jhb at freebsd.org>
To: freebsd-amd64 at freebsd.org
Cc: chifeng <chifeng at gmail.com>, freebsd-gnats-submit at freebsd.org
Subject: Re: amd64/117664: iostat can't display IO current vlaue in first line
Date: Wed, 31 Oct 2007 13:53:35 -0400
On Tuesday 30 October 2007 03:22:39 am chifeng wrote:
> >Number: 117664
> >Category: amd64
> >Synopsis: iostat can't display IO current vlaue in first line
> >Confidential: no
> >Severity: non-critical
> >Priority: low
> >Responsible: freebsd-amd64
> >State: open
> >Class: change-request
> >Submitter-Id: current-users
> >Arrival-Date: Tue Oct 30 07:30:02 UTC 2007
> >Originator: chifeng
> >Release: FreeBSD6.2-Release-p8
> Platform Computing
> FreeBSD cnxabuild.asia.corp.platform.com 6.2-RELEASE-p8 FreeBSD
6.2-RELEASE-p8 #0: Tue Oct 16 12:32:14 CST 2007
root at xabuild.asia.corp.platform.com:/usr/obj/usr/src/sys/PLATFORM amd64
> When I write a shell script plugin for munin, I hope get a current value of
IO statistics. But iostat can't do it, it first statistics that are printed
are avaraged over the system uptime. If I use "iostat -c 2 | tail -1 "
command, this will wait 2s at least.
> so I think for iostat first line, 1) iostat should be display current value,
2) have a parameter to display current value at least.
There isn't a 'current value' for iostat to dump. The kernel just keeps
running counts and iostat simulates a current value by saving the values each
time and computing a delta for each line after the first. However, for the
first line there is no saved value so it cannot compute a delta. Probably
you need to write your own plugin that saves the previous values and computes
deltas when queried similar to how iostat behaves.
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