1 /* $OpenBSD: proc_compare.c,v 1.10 2005/04/11 07:04:47 deraadt Exp $ */
2
3 /*-
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #ifndef lint
33 #if 0
34 static char sccsid[] = "@(#)proc_compare.c 8.2 (Berkeley) 9/23/93";
35 #else
36 static char *rcsid = "$OpenBSD: proc_compare.c,v 1.10 2005/04/11 07:04:47 deraadt Exp $";
37 #endif
38 #endif /* not lint */
39
40 #include <sys/param.h>
41 #include <sys/time.h>
42 #include <sys/sysctl.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 (P_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 #ifdef SONPROC
66 #define ISRUN(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL) || \
67 ((p)->p_stat == SONPROC))
68 #else
69 #define ISRUN(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL))
70 #endif
71 #define TESTAB(a, b) ((a)<<1 | (b))
72 #define ONLYA 2
73 #define ONLYB 1
74 #define BOTH 3
75
76 int
proc_compare(const struct kinfo_proc2 * p1,const struct kinfo_proc2 * p2)77 proc_compare(const struct kinfo_proc2 *p1, const struct kinfo_proc2 *p2)
78 {
79 if (p1 == NULL)
80 return (1);
81 /*
82 * see if at least one of them is runnable
83 */
84 switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
85 case ONLYA:
86 return (0);
87 case ONLYB:
88 return (1);
89 case BOTH:
90 /*
91 * tie - favor one with highest recent cpu utilization
92 */
93 if (p2->p_estcpu > p1->p_estcpu)
94 return (1);
95 if (p1->p_estcpu > p2->p_estcpu)
96 return (0);
97 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
98 }
99 /*
100 * weed out zombies
101 */
102 switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) {
103 case ONLYA:
104 return (1);
105 case ONLYB:
106 return (0);
107 case BOTH:
108 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
109 }
110 /*
111 * pick the one with the smallest sleep time
112 */
113 if (p2->p_slptime > p1->p_slptime)
114 return (0);
115 if (p1->p_slptime > p2->p_slptime)
116 return (1);
117 /*
118 * favor one sleeping in a non-interruptible sleep
119 */
120 if (p1->p_flag & P_SINTR && (p2->p_flag & P_SINTR) == 0)
121 return (1);
122 if (p2->p_flag & P_SINTR && (p1->p_flag & P_SINTR) == 0)
123 return (0);
124 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
125 }
126