Annotation of src/usr.bin/w/proc_compare.c, Revision 1.7
1.7 ! millert 1: /* $OpenBSD: proc_compare.c,v 1.6 2003/06/03 02:56:22 millert Exp $ */
1.2 deraadt 2:
1.1 deraadt 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.
1.6 millert 15: * 3. Neither the name of the University nor the names of its contributors
1.1 deraadt 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
1.3 millert 33: #if 0
1.1 deraadt 34: static char sccsid[] = "@(#)proc_compare.c 8.2 (Berkeley) 9/23/93";
1.3 millert 35: #else
1.7 ! millert 36: static char *rcsid = "$OpenBSD: proc_compare.c,v 1.6 2003/06/03 02:56:22 millert Exp $";
1.3 millert 37: #endif
1.1 deraadt 38: #endif /* not lint */
39:
40: #include <sys/param.h>
41: #include <sys/time.h>
42: #include <sys/proc.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: #define ISRUN(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL))
66: #define TESTAB(a, b) ((a)<<1 | (b))
67: #define ONLYA 2
68: #define ONLYB 1
69: #define BOTH 3
70:
71: int
1.7 ! millert 72: proc_compare(struct proc *p1, struct proc *p2)
1.1 deraadt 73: {
74: if (p1 == NULL)
75: return (1);
76: /*
77: * see if at least one of them is runnable
78: */
79: switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
80: case ONLYA:
81: return (0);
82: case ONLYB:
83: return (1);
84: case BOTH:
85: /*
86: * tie - favor one with highest recent cpu utilization
87: */
88: if (p2->p_estcpu > p1->p_estcpu)
89: return (1);
90: if (p1->p_estcpu > p2->p_estcpu)
91: return (0);
92: return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
93: }
94: /*
95: * weed out zombies
96: */
97: switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) {
98: case ONLYA:
99: return (1);
100: case ONLYB:
101: return (0);
102: case BOTH:
103: return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
104: }
105: /*
106: * pick the one with the smallest sleep time
107: */
108: if (p2->p_slptime > p1->p_slptime)
109: return (0);
110: if (p1->p_slptime > p2->p_slptime)
111: return (1);
112: /*
113: * favor one sleeping in a non-interruptible sleep
114: */
115: if (p1->p_flag & P_SINTR && (p2->p_flag & P_SINTR) == 0)
116: return (1);
117: if (p2->p_flag & P_SINTR && (p1->p_flag & P_SINTR) == 0)
118: return (0);
119: return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
120: }