iopending(1m)

Usage

iopending [-c] [-d device] [-f filename] [-m mount_point] [interval [count]]

Overview

This samples the number of disk events that are pending and plots a distribution graph. By doing this the "serialness" or "parallelness" of disk behaviour can be distinguished. A high occurance of a pending value of more than 1 is an indication of saturation.

Since this uses DTrace, only users with root privileges can run this command.

Options

-c: clear screen

-d device: instance name to snoop (eg, dad0)

-f filename: full pathname of file to snoop

-m mount_point: mountpoint for filesystem to snoop

Examples

`Default output, print I/O summary every 1 second,`	# `iopending`
`Print 10 second samples,`	# `iopending` 10
`Print 12 x 5 second samples,`	# `iopending` 5 12
`Snoop events on the root filesystem only,`	# `iopending` -m /

Fields

`value`	number of pending events, 0 == idle
`count`	number of samples @ 1000 Hz
`load`	1 min load average
`disk_r`	total disk read Kb for sample
`disk_w`	total disk write Kb for sample

Idea

Dr Rex di Bona

Documentation

See the DTraceToolkit for further documentation under the Docs directory. The DTraceToolkit docs may include full worked examples with verbose descriptions explaining the output.

Exit

iopending will run forever until Ctrl-C is hit, or the specified count is reached.

Releases

115 releases since Mac OS X 10.5; the text changed 1 time.