1 /* $OpenBSD: proc_compare.c,v 1.17 2022/02/22 17:35:01 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 #include <sys/types.h>
33 #include <sys/signal.h>
34 #include <sys/proc.h>
35 #include <sys/sysctl.h>
36 #include <sys/time.h>
37
38 #include "extern.h"
39
40 /*
41 * Returns 1 if p2 is "better" than p1
42 *
43 * The algorithm for picking the "interesting" process is thus:
44 *
45 * 1) Only foreground processes are eligible - implied.
46 * 2) Runnable processes are favored over anything else. The runner
47 * with the highest cpu utilization is picked (p_estcpu). Ties are
48 * broken by picking the highest pid.
49 * 3) The sleeper with the shortest sleep time is next. With ties,
50 * we pick out just "short-term" sleepers (P_SINTR == 0).
51 * 4) Further ties are broken by picking the highest pid.
52 *
53 * If you change this, be sure to consider making the change in the kernel
54 * too (^T in kern/tty.c).
55 *
56 * TODO - consider whether pctcpu should be used.
57 */
58
59 #define ISRUN(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL) || \
60 ((p)->p_stat == SONPROC))
61 #define TESTAB(a, b) ((a)<<1 | (b))
62 #define ONLYA 2
63 #define ONLYB 1
64 #define BOTH 3
65
66 int
proc_compare(const struct kinfo_proc * p1,const struct kinfo_proc * p2)67 proc_compare(const struct kinfo_proc *p1, const struct kinfo_proc *p2)
68 {
69 if (p1 == NULL)
70 return (1);
71 /*
72 * see if at least one of them is runnable
73 */
74 switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
75 case ONLYA:
76 return (0);
77 case ONLYB:
78 return (1);
79 case BOTH:
80 /*
81 * tie - favor one with highest recent cpu utilization
82 */
83 if (p2->p_estcpu > p1->p_estcpu)
84 return (1);
85 if (p1->p_estcpu > p2->p_estcpu)
86 return (0);
87 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
88 }
89 /*
90 * weed out zombies
91 */
92 switch (TESTAB(p1->p_stat == SDEAD, p2->p_stat == SDEAD)) {
93 case ONLYA:
94 return (1);
95 case ONLYB:
96 return (0);
97 case BOTH:
98 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
99 }
100 /*
101 * pick the one with the smallest sleep time
102 */
103 if (p2->p_slptime > p1->p_slptime)
104 return (0);
105 if (p1->p_slptime > p2->p_slptime)
106 return (1);
107 /*
108 * favor one sleeping in a non-interruptible sleep
109 */
110 if (p1->p_flag & P_SINTR && (p2->p_flag & P_SINTR) == 0)
111 return (1);
112 if (p2->p_flag & P_SINTR && (p1->p_flag & P_SINTR) == 0)
113 return (0);
114 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
115 }
116