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1.1 root 1: /*-
2: * Copyright (c) 1990 The Regents of the University of California.
3: * All rights reserved.
4: *
5: * Redistribution and use in source and binary forms are permitted provided
6: * that: (1) source distributions retain this entire copyright notice and
7: * comment, and (2) distributions including binaries display the following
8: * acknowledgement: ``This product includes software developed by the
9: * University of California, Berkeley and its contributors'' in the
10: * documentation or other materials provided with the distribution and in
11: * all advertising materials mentioning features or use of this software.
12: * Neither the name of the University nor the names of its contributors may
13: * be used to endorse or promote products derived from this software without
14: * specific prior written permission.
15: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
16: * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
17: * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
18: */
19:
20: #ifndef lint
21: static char sccsid[] = "@(#)proc_compare.c 5.3 (Berkeley) 6/26/90";
22: #endif /* not lint */
23:
24: /*
25: * Returns 1 if p2 is more active than p1
26: *
27: * The algorithm for picking the "more active" process is thus:
28: *
29: * 1) Runnable processes are favored over anything
30: * else. The runner with the highest cpu
31: * utilization is picked (p_cpu). Ties are
32: * broken by picking the highest pid.
33: * 2) Next, the sleeper with the shortest sleep
34: * time is favored. With ties, we pick out
35: * just short-term sleepers (p_pri <= PZERO).
36: * Further ties are broken by picking the highest
37: * pid.
38: *
39: * NOTE - if you change this, be sure to consider making
40: * the change in the kernel too (^T in kern/tty.c).
41: *
42: * TODO - consider whether pctcpu should be used
43: *
44: */
45:
46: #include <sys/param.h>
47: #include <sys/time.h>
48: #include <sys/proc.h>
49:
50: #define isrun(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL))
51:
52: #define TESTAB(a, b) ((a)<<1 | (b))
53: #define ONLYA 0x10
54: #define ONLYB 0x01
55: #define BOTH 0x11
56:
57: proc_compare(p1, p2)
58: register struct proc *p1, *p2;
59: {
60:
61: if (p1 == NULL)
62: return (1);
63: /*
64: * see if at least one of them is runnable
65: */
66: switch (TESTAB(isrun(p1), isrun(p2))) {
67: case ONLYA:
68: return (1);
69: case ONLYB:
70: return (0);
71: case BOTH:
72: /*
73: * tie - favor one with highest recent cpu utilization
74: */
75: if (p2->p_cpu > p1->p_cpu)
76: return (1);
77: if (p1->p_cpu > p2->p_cpu)
78: return (0);
79: return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
80: }
81: /*
82: * weed out zombies
83: */
84: switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) {
85: case ONLYA:
86: return (1);
87: case ONLYB:
88: return (0);
89: case BOTH:
90: return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
91: }
92: /*
93: * pick the one with the smallest sleep time
94: */
95: if (p2->p_slptime > p1->p_slptime)
96: return (0);
97: if (p1->p_slptime > p2->p_slptime)
98: return (1);
99: /*
100: * favor one sleeping in a non-interruptible sleep
101: */
102: if (p1->p_flag&SSINTR && (p2->p_flag&SSINTR) == 0)
103: return (1);
104: if (p2->p_flag&SSINTR && (p1->p_flag&SSINTR) == 0)
105: return (0);
106: return(p2->p_pid > p1->p_pid); /* tie - return highest pid */
107: }
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