proc_compare.c revision 69896 
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#ifndef lint
35#if 0
36static char sccsid[] = "@(#)proc_compare.c	8.2 (Berkeley) 9/23/93";
37#endif
38static const char rcsid[] =
39  "$FreeBSD: head/usr.bin/w/proc_compare.c 69896 2000-12-12 07:25:57Z mckusick $";
40#endif /* not lint */
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 (P_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#define ISRUN(p)	(((p)->ki_stat == SRUN) || ((p)->ki_stat == SIDL))
68#define TESTAB(a, b)    ((a)<<1 | (b))
69#define ONLYA   2
70#define ONLYB   1
71#define BOTH    3
72
73int
74proc_compare(p1, p2)
75	struct kinfo_proc *p1, *p2;
76{
77
78	if (p1 == NULL)
79		return (1);
80	/*
81	 * see if at least one of them is runnable
82	 */
83	switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
84	case ONLYA:
85		return (0);
86	case ONLYB:
87		return (1);
88	case BOTH:
89		/*
90		 * tie - favor one with highest recent cpu utilization
91		 */
92		if (p2->ki_estcpu > p1->ki_estcpu)
93			return (1);
94		if (p1->ki_estcpu > p2->ki_estcpu)
95			return (0);
96		return (p2->ki_pid > p1->ki_pid);	/* tie - return highest pid */
97	}
98	/*
99 	 * weed out zombies
100	 */
101	switch (TESTAB(p1->ki_stat == SZOMB, p2->ki_stat == SZOMB)) {
102	case ONLYA:
103		return (1);
104	case ONLYB:
105		return (0);
106	case BOTH:
107		return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */
108	}
109	/*
110	 * pick the one with the smallest sleep time
111	 */
112	if (p2->ki_slptime > p1->ki_slptime)
113		return (0);
114	if (p1->ki_slptime > p2->ki_slptime)
115		return (1);
116	/*
117	 * favor one sleeping in a non-interruptible sleep
118	 */
119	if (p1->ki_flag & P_SINTR && (p2->ki_flag & P_SINTR) == 0)
120		return (1);
121	if (p2->ki_flag & P_SINTR && (p1->ki_flag & P_SINTR) == 0)
122		return (0);
123	return (p2->ki_pid > p1->ki_pid);		/* tie - return highest pid */
124}
125