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33 * @(#)proc_compare.c 8.2 (Berkeley) 9/23/93
36 #include <sys/param.h>
43 * Returns 1 if p2 is "better" than p1
45 * The algorithm for picking the "interesting" process is thus:
47 * 1) Only foreground processes are eligible - implied.
48 * 2) Runnable processes are favored over anything else. The runner
49 * with the highest cpu utilization is picked (p_estcpu). Ties are
50 * broken by picking the highest pid.
51 * 3) The sleeper with the shortest sleep time is next. With ties,
52 * we pick out just "short-term" sleepers (P_SINTR == 0).
53 * 4) Further ties are broken by picking the highest pid.
55 * If you change this, be sure to consider making the change in the kernel
56 * too (^T in kern/tty.c).
58 * TODO - consider whether pctcpu should be used.
61 #define ISRUN(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL))
62 #define TESTAB(a, b) ((a)<<1 | (b))
69 register struct proc *p1, *p2;
75 * see if at least one of them is runnable
77 switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
84 * tie - favor one with highest recent cpu utilization
86 if (p2->p_estcpu > p1->p_estcpu)
88 if (p1->p_estcpu > p2->p_estcpu)
90 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
95 switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) {
101 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
104 * pick the one with the smallest sleep time
106 if (p2->p_slptime > p1->p_slptime)
108 if (p1->p_slptime > p2->p_slptime)
111 * favor one sleeping in a non-interruptible sleep
113 if (p1->p_flag & P_SINTR && (p2->p_flag & P_SINTR) == 0)
115 if (p2->p_flag & P_SINTR && (p1->p_flag & P_SINTR) == 0)
117 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */