NAME

iotop - display top disk I/O events by process. Uses DTrace.

SYNOPSIS

iotop [-C] [-D|-o|-P] [-j|-Z] [-d device] [-f filename] [-m mount_point] [-t top] [interval [count]]

DESCRIPTION

iotop tracks disk I/O by process, and prints a summary report that is refreshed every interval.

This is measuring disk events that have made it past system caches.

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

OPTIONS

-C: don't clear the screen
-D: print delta times - elapsed, us
-j: print project ID
-o: print disk delta times, us
-P: print %I/O (disk delta times)
-Z: print zone ID
-d device: instance name to snoop (eg, dad0)
-f filename: full pathname of file to snoop
-m mount_point: mountpoint for filesystem to snoop
-t top: print top number only

EXAMPLES

Default output, print summary every 5 seconds: # iotop
One second samples,: # iotop 1
print %I/O (time based),: # iotop -P
Snoop events on the root filesystem only,: # iotop -m /
Print top 20 lines only,: # iotop -t 20
Print 12 x 5 second samples, scrolling,: # iotop -C 5 12

FIELDS

UID: user ID
PID: process ID
PPID: parent process ID
PROJ: project ID
ZONE: zone ID
CMD: command name for the process
DEVICE: device name
MAJ: device major number
MIN: device minor number
D: direction, Read or Write
BYTES: total size of operations, bytes
ELAPSED: total elapsed times from request to completion, us (this is the elapsed time from the disk request (strategy) to the disk completion (iodone))
DISKTIME: total times for disk to complete request, us (this is the time for the disk to complete that event since it's last event (time between iodones), or, the time to the strategy if the disk had been idle)
%I/O: percent disk I/O, based on time (DISKTIME)
load: 1 minute load average
disk_r: total disk read Kb for sample
disk_w: total disk write Kb for sample

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

iotop will run forever until Ctrl-C is hit, or the specified interval is reached.

AUTHOR

Brendan Gregg [Sydney, Australia]