10-14-2008
To answer your questions, yes it is possible for short-lived processes to never show up. In fact it is very unlikely that a short lived process will show up in ps or top. Those programs read the process table with techniques that are almost as fast as a memory to memory data move. Once they have this snapshot, they prepare a report. top repeats this every n seconds, but top presents you with a program...it does not want to show all processes, just the "top" ones. You have a better shot with ps. A short-lived process can be gone in well under a tenth of a second.... let's say that yours is lasting exactly one tenth of a second... That means that ps must capture a process table snapshot sometime during that tenth of a second. This is very hard to arrange in a reliable fashion. A very clever wrapper program that runs both ps and your program nearly simultaneously might be able to do it.
But if the program shows up in glance but not ps/top, I tend to suspect something else. It could be that the program is destroying it's command line. You might try: ps -el and see if it shows up.
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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.
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)