proc_compare.c revision 87674 
1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include <sys/cdefs.h>
35
36__FBSDID("$FreeBSD: head/usr.bin/w/proc_compare.c 87674 2001-12-11 22:18:47Z markm $");
37
38#ifndef lint
39static const char sccsid[] = "@(#)proc_compare.c	8.2 (Berkeley) 9/23/93";
40#endif
41
42#include <sys/param.h>
43#include <sys/time.h>
44#include <sys/user.h>
45
46#include "extern.h"
47
48/*
49 * Returns 1 if p2 is "better" than p1
50 *
51 * The algorithm for picking the "interesting" process is thus:
52 *
53 *	1) Only foreground processes are eligible - implied.
54 *	2) Runnable processes are favored over anything else.  The runner
55 *	   with the highest cpu utilization is picked (p_estcpu).  Ties are
56 *	   broken by picking the highest pid.
57 *	3) The sleeper with the shortest sleep time is next.  With ties,
58 *	   we pick out just "short-term" sleepers (PS_SINTR == 0).
59 *	4) Further ties are broken by picking the highest pid.
60 *
61 * If you change this, be sure to consider making the change in the kernel
62 * too (^T in kern/tty.c).
63 *
64 * TODO - consider whether pctcpu should be used.
65 */
66
67#include <sys/cdefs.h>
68
69__FBSDID("$FreeBSD: head/usr.bin/w/proc_compare.c 87674 2001-12-11 22:18:47Z markm $");
70
71#define ISRUN(p)	(((p)->ki_stat == SRUN) || ((p)->ki_stat == SIDL))
72#define TESTAB(a, b)    ((a)<<1 | (b))
73#define ONLYA   2
74#define ONLYB   1
75#define BOTH    3
76
77int
78proc_compare(p1, p2)
79	struct kinfo_proc *p1, *p2;
80{
81
82	if (p1 == NULL)
83		return (1);
84	/*
85	 * see if at least one of them is runnable
86	 */
87	switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
88	case ONLYA:
89		return (0);
90	case ONLYB:
91		return (1);
92	case BOTH:
93		/*
94		 * tie - favor one with highest recent cpu utilization
95		 */
96		if (p2->ki_estcpu > p1->ki_estcpu)
97			return (1);
98		if (p1->ki_estcpu > p2->ki_estcpu)
99			return (0);
100		return (p2->ki_pid > p1->ki_pid);	/* tie - return highest pid */
101	}
102	/*
103 	 * weed out zombies
104	 */
105	switch (TESTAB(p1->ki_stat == SZOMB, p2->ki_stat == SZOMB)) {
106	case ONLYA:
107		return (1);
108	case ONLYB:
109		return (0);
110	case BOTH:
111		return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */
112	}
113	/*
114	 * pick the one with the smallest sleep time
115	 */
116	if (p2->ki_slptime > p1->ki_slptime)
117		return (0);
118	if (p1->ki_slptime > p2->ki_slptime)
119		return (1);
120	/*
121	 * favor one sleeping in a non-interruptible sleep
122	 */
123	if (p1->ki_tdflags & TDF_SINTR && (p2->ki_tdflags & TDF_SINTR) == 0)
124		return (1);
125	if (p2->ki_tdflags & TDF_SINTR && (p1->ki_tdflags & TDF_SINTR) == 0)
126		return (0);
127	return (p2->ki_pid > p1->ki_pid);	/* tie - return highest pid */
128}
129