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