# The kpm Handbook

Mario
Weilguni

    mweilguni@kde.org

Version 1.3k1, 02 Februar 1998

This Handbook describes kpm 1.3k1, an utility for information and management of processes.

The KPm Handbook

KDE
KPm
process manager
top

## General information

### What is kpm?

kpm allows you to view and modify the processes of you Linux computer. It shows detailed information of running processes, computer resources like RAM, swap space, CPU utilization, uptime and so on. You can kill processes and modify their priority. If you are running it as super-user, it gives you abilty to change scheduling settings too.

### Legal stuff

kpm is heavily based on Mattias Engdegård's `qps`. The main difference between kpm and qps is the KDE interface. kpm adheres to most KDE standard, uses the KDE config files and has session managment. Some features of qps were removed (i.e. the ability to display Mac OS7 style tables or special checkbox widgets).

qps (and thus kpm) is published under the GNU General Public License (GNU GPL).

### Requirements for kpm

- A Linux 2.0 or higher operating system. kpm makes excessive use of Linux's `/proc` filesystem. Unfortunatly this is not portable to other systems, because every UNIX system seems to have it's own way of gathering process information.

- K Desktop Environment Beta2 or better

- Qt 1.31. Because KDE is based on Qt, this is no problem.

- Your Linux kernel must be compiled with `proc` filesystem support. Since many things like top won't even work without that, this is standard for most kernels.

## The menu

### Window menu

Iconify

  Iconifies the main window. When iconfied, kpm uses far less CPU time because there is no need to update the process list. If you use KWM as window manager and the option "Dock into kpanel" is checked, you will see a little icon in kpanel displaying the average system load. Under other window managers like fvwm, kpm's icon itself will show the load (but this depends on how the window manager is configured).

Quit

  Exits kpm (closing the main window has the same effect).

### Process menu

Renice

  Allows you to modify the priority of the marked process (or all marked processes). Under Linux a process has a priority (nice value) ranging from -20 (best) to +20 (worst), thus increasing the nice value gives a process less CPU time. You are not allowed to lower the nice value (improve its priority) unless are the super-user. This means that, as an ordinary user, you cannot lower the nice value of a process even if you raised it before.

  Of course you are only allowed to alter the priority of your own processes. The super-user is allowed to modify the priority for any process, and he may lower the priority.

Change scheduling

  This option is only available to root. The Change Scheduling... dialog allows the super-user to change the scheduling policy of the selected processes (using the Posix.1b real-time extensions present in the Linux 2.0.x kernels). Normal processes are set to SCHED&lowbar;OTHER and have static priority 0; (soft) real-time processes have the policy SCHED&lowbar;FIFO or SCHED&lowbar;RR and a static priority in the range of 1 to 99.

Socket info

  Displays a list of TCP and UDP sockets used by the selected processes.

### Signal menu

The signal menu allows you to send various signals to all marked processes. Be careful when doing this, especially if more than one process is marked. The standard Linux signals are explained here.

### View menu

Refresh process list

  Immediatly updates the process list. This is very useful if you use rather long update periods. You can also do this by pressing the update button in the toolbar or by pressing the Space key.

All processes

  Displays all processes.

Your processes

  Display your processes, including those running under a different user (i.e. SETUID root programs you started)

Non-root processes

  Display all processes except those started by root.

Running processes

  Show only running processes (running or on the run queue)

User fields

  The process list will show the most interesting process fields. This are those fields typically displayed by "top".

Job fields

  Displays most relevant fields for job-control.

Memory fields

  Shows information about memory usage, page faults...

## kpm main window

### Explaining the fields

PID - Process ID

  Each process has a unique process ID number, starting at 1 and going up. When a new process is created, the next unused PID is allocated. PIDs are (currently) 16-bit signed integers, so they wrap around at 32767; this is normal behaviour and nothing to worry about.

PPID - Parent process ID

  Every process has one parent process. The exception is process 1 (init), which is the root of the process hierarchy; it has no parent.

PGID - Process group ID

  Each process is member of one process group. Process groups are used for distribution of signals, and by terminals to arbitrate requests for their input: processes that have the same process group as the terminal are foreground and may read, while others will block with a signal if they attempt to read.

SID - Session ID

  Session IDs are used mainly to determine what happens at terminal hangups.

TTY - Controlling tty

  The controlling terminal (tty) is usually the device (serial port, pty etc) from which the process was started, and which it uses for input or output. Not all processes have a controlling terminal. Kpm scans the /dev directory to determine the name of the terminal, but this might fail. To save space, only the two last characters of the tty name is shown (thus /dev/ttyp6 is shown as p6)

TPGID - Process group ID of tty owner

  A tty in use is owned by a process. This is the PGID of that process.

USER - Process owner

  This is the name of the (real) user owning the process. If the effective user ID of a process is different from the real user ID, this is indicated by a trailing "*" or "+". The asterisk is used when the effective user is the super-user (this usually indicates a binary that is set-uid to root).

NICE - Time-sharing priority

  The nice value determines how often a process is allowed to run, and the length of its timeslice. The value is in the range -20 to 20, 0 being the default. Lower numbers give more CPU time to a process. Only the super-user may lower the nice value.

PRI - Length of next timeslice

  This is the maximal length of the process's next timeslice (or what is left of its current timeslice, if it is the currently running process). The number is rescaled to the -20..20 interval, smaller number indicating a longer timeslice.

PLCY - Scheduling policy

  FIFO (F) and Round-Robin (R) are realtime scheduling policies; OTHER (O) is the normal Unix time-sharing policy. F and R processes have a realtime priority between 1 and 99. A process will run as long as there is no runnable process with higher priority. Round-Robin processes will run for the length of one time-slice, after which they are placed last in the queue of their priority. FIFO processes run until they give up their CPU time (by sleeping or blocking) or pre-empted by a process with higher priority. Only the super-user (root) may change the scheduling policy.

RPRI - Realtime priority

  Realtime processes (FIFO and Round-Robin) have priorities between 1 and 99. A process will pre-empt any other process that has lower priority. Normal time-sharing processes (policy O) all have priority 0. Only the super-user (root) may change the realtime priority.

MAJFLT - Number of major faults occured

  A page fault occurs when a process attempts to read or write from a memory page that isn't present in RAM. A major page fault is when disk access is involved, such as swapping in and out memory pages.

MINFLT - Number of minor faults occured

  A page fault occurs when a process attempts to read or write from a memory page that isn't present in RAM, or write to a page that isn't writeable. A minor fault is when there is no disk access involved, for instance when writing to a copy-on-write shared page.

TRS - Text resident set size (Kbytes)

  This is the size of the text (that is, executable code) of the process that is currently present in RAM.

DRS - Data resident set size (Kbytes)

  This is the size of the data (not executable code) of the process that is currently present in RAM.

SIZE - virtual image size of process (Kbytes)

  This is the total size of the image of the process. This includes all code, data, and shared libraries used by the process, including pages that have been swapped out.

SWAP - Kbytes on swap device

  This is simply the difference between SIZE and RSS, in other words how much of a process that resides on disk.

RSS - resident set size (Kbytes)

  This is the size of the part of the process (code and data) that actually resides in RAM, including shared libraries. This gives a fair approximation of how much RAM a process is using.

SHARE - shared memory (Kbytes)

  This is the amount of memory that the process shares with other processes. It doesn't mean that any of it is actually used by any other process, just that it is possible.

DT - number of dirty pages

  This is the number (not the number of bytes!) of pages in RAM that have been modified since they were last written to disk. Dirty pages have to be written to disk before they are freed and used for something else.

STAT - state of the process

  The process is at any time in one of the following states:

  - R (running): the process is running on a cpu or is ready to run.

  - S (sleeping): the process is waiting for an event to occur (such as I/O or a timer).

  - D (uninterruptible sleep): the process is waiting for an event to occur, without being interruptible (usually waiting in a device driver).

  - T (stopped): the process is stopped, or being traced by another process.

  - Z (zombie): the process has terminated, but its parent hasn't mourned its death yet.

  - If the process is completely swapped out (has no resident pages), a 'W' is shown in the field. (This is also true for kernel processes, such as kswapd.)

FLAGS - process flags (hex)

  This contains some additional information about the state of a process. Refer to the Linux kernel source for details.

WCHAN - function where process is sleeping

  If the process is waiting for something to happen, this is the kernel function where it is stuck. (Leading do&lowbar; or sys&lowbar; is stripped from the name to make it shorter.)

UID - numerical user ID

  This is the ID of the (real) user owning the process.

&percnt;WCPU - weighted percentage of CPU

  This is the percentage of CPU time the process is using, averaged over the last 30 seconds (exponentially decaying average).

&percnt;CPU - percentage of CPU since last update

  This is how much of the CPU time the process used since the last update of kpm's process table.

&percnt;MEM - percentage of memory used

  This is how large part of the total RAM that is used by the process (as resident size). Shared libraries count, so this is an overstatement.

START - time process started

  This is when the process was created.

TIME - total CPU time used

  This is how much CPU time the process has used since it was started.

COMM - command that started the process

  This is the command (file name) that started the process. Long names are truncated.

CMDLINE - command line that started the process

  This the command line, including arguments, that started the process. If "Hide Command Path" in the Options menu is selected, then the leading path of the command name is stripped. Processes swapped out may show just the command name in parentheses (this is true for kernel processes as well).

## Appendix

### UNIX Signals

These are the signals as explained on the manual page of signal(7). For details consult the manual page with:

`man 7 signal`

The following signals are defined by Posix and can be sent by kpm:

- SIGHUP: Hangup detected on controlling terminal or death of controlling process

- SIGINT: Interrupt from keyboard

- SIGQUIT: Quit from keyboard

- SIGILL: Illegal Instruction

- SIGABRT: Abort signal from abort(3)

- SIGFPE: Floating point exception

- SIGKILL: Kill signal

- SIGSEG: Invalid memory reference

- SIGPIPE: Broken pipe: write to pipe with no readers

- SIGALRM: Timer signal from alarm(1)

- SIGTERM: Termination signal

- SIGUSR1: User-defined signal 1

- SIGUSR2: User-defined signal 2

- SIGCHLD: Child stopped or terminated

- SIGCONT: Continue if stopped

- SIGSTOP: Stop process

- SIGTSTP: Stop typed at tty

- SIGTTIN: tty input for background process

- SIGTTOU: tty output for background process

These signals aren't defined by Posix, nor available from kpm (yet)

- SIGTRAP: Trace/breakpoint trap

- SIGIOT: IOT trap. A synonym for SIGABRT

- SIGBUS: Bus error

- SIGSYS: Bad argument to routine (SVID)

- SIGSTKFLT: Stack fault on coprocessor

- SIGURG: Urgent condition on socket (4.2 BSD)

- SIGIO: I/O now possible (4.2 BSD)

- SIGPOLL: synonym for SIGIO (System V)

- SIGCLD: synonym for SIGCHLD

- SIGXCPU: CPU time limit exceeded (4.2 BSD)

- SIGXFSZ: File size limit exceeded (4.2 BSD)

- SIGVTALRM: Virtual alarm clock (4.2 BSD)

- SIGPROF: Profile alarm clock

- SIGPWR: Power failure (System V)

- SIGINFO: A synonym for SIGPWR

- SIGLOST: File lock lost

- SIGWINCH: Window resize signal (4.3 BSD, Sun)

- SIGUNUSED: Unused signal

### Known bugs and problems

- kpm sometimes dies with a segmentation fault if more than one process is marked and the list is updated. I've no clue why...

- The info bar and the process list itself are optimized for 12pt fonts. It will look good enough with fonts up to 14pt, but look very ugly for bigger fonts.

- kpm can consume a lot of CPU resources if the update period is too small. On my system (AMD K6PR200) it uses approximatly 5 percent CPU time with an update period of one second. This heavily depends on the total number of processes (all processes, not only those displayed) and can be much higher than this.

- The &percnt;CPU number isn't accurate at very short update periods due to timer granularity.

- The WCHAN field isn't correct if a process sleeps in a location outside those in `System.map` (for instance, in a kernel module). In these cases, the last entry in `System.map` will be showed (something like `&lowbar;end`).

- kpm doesn't handle more than one process with the same PID. This can occur when using CLONE&lowbar;PID with the clone() system call.