\" $NetBSD: proc_compare.3,v 1.2 2011/10/21 12:58:53 wiz Exp $

\" $NetBSD: proc_compare.3,v 1.2 2011/10/21 12:58:53 wiz Exp $
\"
\" Copyright (c) 2011 The NetBSD Foundation, Inc.
\" All rights reserved.
\"
\" This code is derived from software contributed to The NetBSD Foundation
\" by Christos Zoulas.
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Dd October 20, 2011
Dt PROC_COMPARE 3
Os
Sh NAME
Nm proc_compare
Nd compare two processes' interactivity
Sh LIBRARY
Lb libutil
Sh SYNOPSIS
In sys/sysctl.h
Ft int
Fn "proc_compare" "const struct kinfo_proc2 *p1" "const struct kinfo_lwp *l1" \
"const struct kinfo_proc2 *p2" "const struct kinfo_lwp *l2"
Sh DESCRIPTION
The
Fn proc_compare
function compares two processes that are on the same terminal for their
interactivity.
This means that the process returned is the one that has a better chance
being the active foreground process on that tty.
This algorithm is used in the kernel for
Dv SIGINFO
reporting and in userland by
Xr w 1 .
Pp
The algorithm used is as follows:
Bl -bullet -compact -offset indent
It
If one of them is runnable, it is preferred.
It
If both are runnable, the one with the largest CPU percent is preferred.
It
In a CPU percent tie, the one started more recently wins.
It
If none are runnable, and one of them is a zombie, the non-zombie is preferred
It
If both are zombies, the one started more recently wins.
It
If neither is a zombie, the one with the smaller sleep time wins.
It
In a tie, and one is sleeping in non-interruptible sleep, prefer that one.
It
If both are in the same state, the one started more recently is preferred.
El
In all cases where the most recently started wins, if there was no winner,
the one with the largest PID wins.
Sh RETURN VALUES
The
Fn proc_compare
function returns
Dv 0
if
Fa p1
is to be preferred
and
Dv 1
if
Fa p2
is to be preferred.
Sh SEE ALSO
Xr w 1
Sh HISTORY
The
Fn proc_compare
was extracted from
Pa src/sys/kern/tty.c
and
Pa src/usr.bin/w/proc_compare.c
and merged in
Nx 6.0 .