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iotop(8) [centos man page]

IOTOP(8)						      System Manager's Manual							  IOTOP(8)

NAME
iotop - simple top-like I/O monitor SYNOPSIS
iotop [OPTIONS] DESCRIPTION
iotop watches I/O usage information output by the Linux kernel (requires 2.6.20 or later) and displays a table of current I/O usage by pro- cesses or threads on the system. At least the CONFIG_TASK_DELAY_ACCT, CONFIG_TASK_IO_ACCOUNTING, CONFIG_TASKSTATS and CONFIG_VM_EVENT_COUN- TERS options need to be enabled in your Linux kernel build configuration. iotop displays columns for the I/O bandwidth read and written by each process/thread during the sampling period. It also displays the per- centage of time the thread/process spent while swapping in and while waiting on I/O. For each process, its I/O priority (class/level) is shown. In addition, the total I/O bandwidth read and written during the sampling period is displayed at the top of the interface. Total DISK READ and Total DISK WRITE values represent total read and write bandwidth between processes and kernel threads on the one side and kernel block device subsystem on the other. While Actual DISK READ and Actual DISK WRITE values represent corresponding bandwidths for actual disk I/O between kernel block device subsystem and underlying hardware (HDD, SSD, etc.). Thus Total and Actual values may not be equal at any given moment of time due to data caching and I/O operations reordering that take place inside Linux kernel. Use the left and right arrows to change the sorting, r to reverse the sorting order, o to toggle the --only option, p to toggle the --pro- cesses option, a to toggle the --accumulated option, q to quit or i to change the priority of a thread or a process' thread(s). Any other key will force a refresh. OPTIONS
--version Show the version number and exit -h, --help Show usage information and exit -o, --only Only show processes or threads actually doing I/O, instead of showing all processes or threads. This can be dynamically toggled by pressing o. -b, --batch Turn on non-interactive mode. Useful for logging I/O usage over time. -n NUM, --iter=NUM Set the number of iterations before quitting (never quit by default). This is most useful in non-interactive mode. -d SEC, --delay=SEC Set the delay between iterations in seconds (1 second by default). Accepts non-integer values such as 1.1 seconds. -p PID, --pid=PID A list of processes/threads to monitor (all by default). -u USER, --user=USER A list of users to monitor (all by default) -P, --processes Only show processes. Normally iotop shows all threads. -a, --accumulated Show accumulated I/O instead of bandwidth. In this mode, iotop shows the amount of I/O processes have done since iotop started. -k, --kilobytes Use kilobytes instead of a human friendly unit. This mode is useful when scripting the batch mode of iotop. Instead of choosing the most appropriate unit iotop will display all sizes in kilobytes. -t, --time Add a timestamp on each line (implies --batch). Each line will be prefixed by the current time. -q, --quiet suppress some lines of header (implies --batch). This option can be specified up to three times to remove header lines. -q column names are only printed on the first iteration, -qq column names are never printed, -qqq the I/O summary is never printed. SEE ALSO
ionice(1), top(1), vmstat(1), atop(1), htop(1) AUTHOR
iotop was written by Guillaume Chazarain. This manual page was started by Paul Wise for the Debian project and is placed in the public domain. April 2009 IOTOP(8)

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iotop(1m)							   USER COMMANDS							 iotop(1m)

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 ver- bose 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] SEE ALSO
iosnoop(1M), dtrace(1M) version 0.75 Oct 25, 2005 iotop(1m)

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