iopending(1m) USER COMMANDS iopending(1m)

iopending - plot number of pending disk events. Uses DTrace.

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

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.

clear screen
instance name to snoop (eg, dad0)
full pathname of file to snoop
mountpoint for filesystem to snoop

# iopending
# iopending 10
# iopending 5 12
# iopending -m /

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

Dr Rex di Bona

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

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

Brendan Gregg [Sydney, Australia]

iosnoop(1M), iotop(1M), dtrace(1M)

November 1, 2005 version 0.60