projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 00fe0339 MT |
1 | /*- |
| 2 | * Copyright (c) 1990 The Regents of the University of California. | |
| 3 | * All rights reserved. | |
| 4 | * | |
| 5 | * %sccs.include.redist.c% | |
| 6 | */ | |
| 7 | ||
| 8 | #ifndef lint | |
| f96f3040 | 9 | static char sccsid[] = "@(#)proc_compare.c 5.4 (Berkeley) %G%"; |
| 00fe0339 MT |
10 | #endif /* not lint */ |
| 11 | ||
| 12 | /* | |
| 13 | * Returns 1 if p2 is more active than p1 | |
| 14 | * | |
| d715ab21 | 15 | * The algorithm for picking the "more active" process is thus: |
| 00fe0339 MT |
16 | * |
| 17 | * 1) Runnable processes are favored over anything | |
| 18 | * else. The runner with the highest cpu | |
| 19 | * utilization is picked (p_cpu). Ties are | |
| 20 | * broken by picking the highest pid. | |
| 21 | * 2) Next, the sleeper with the shortest sleep | |
| 22 | * time is favored. With ties, we pick out | |
| 23 | * just short-term sleepers (p_pri <= PZERO). | |
| 24 | * Further ties are broken by picking the highest | |
| 25 | * pid. | |
| 26 | * | |
| d715ab21 MT |
27 | * NOTE - if you change this, be sure to consider making |
| 28 | * the change in the kernel too (^T in kern/tty.c). | |
| 29 | * | |
| 30 | * TODO - consider whether pctcpu should be used | |
| 00fe0339 MT |
31 | * |
| 32 | */ | |
| d715ab21 MT |
33 | |
| 34 | #include <sys/param.h> | |
| 35 | #include <sys/time.h> | |
| 36 | #include <sys/proc.h> | |
| 37 | ||
| 00fe0339 | 38 | #define isrun(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL)) |
| d715ab21 | 39 | |
| 41a3e0d2 | 40 | #define TESTAB(a, b) ((a)<<1 | (b)) |
| f96f3040 MT |
41 | #define ONLYA 2 |
| 42 | #define ONLYB 1 | |
| 43 | #define BOTH 3 | |
| 41a3e0d2 | 44 | |
| 00fe0339 MT |
45 | proc_compare(p1, p2) |
| 46 | register struct proc *p1, *p2; | |
| 47 | { | |
| 48 | ||
| 49 | if (p1 == NULL) | |
| 50 | return (1); | |
| 51 | /* | |
| 52 | * see if at least one of them is runnable | |
| 53 | */ | |
| 41a3e0d2 MT |
54 | switch (TESTAB(isrun(p1), isrun(p2))) { |
| 55 | case ONLYA: | |
| 00fe0339 | 56 | return (0); |
| f96f3040 MT |
57 | case ONLYB: |
| 58 | return (1); | |
| 41a3e0d2 | 59 | case BOTH: |
| 00fe0339 MT |
60 | /* |
| 61 | * tie - favor one with highest recent cpu utilization | |
| 62 | */ | |
| 63 | if (p2->p_cpu > p1->p_cpu) | |
| 64 | return (1); | |
| 65 | if (p1->p_cpu > p2->p_cpu) | |
| 66 | return (0); | |
| 67 | return (p2->p_pid > p1->p_pid); /* tie - return highest pid */ | |
| 68 | } | |
| 41a3e0d2 MT |
69 | /* |
| 70 | * weed out zombies | |
| 71 | */ | |
| 72 | switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) { | |
| 73 | case ONLYA: | |
| 74 | return (1); | |
| 75 | case ONLYB: | |
| 76 | return (0); | |
| 77 | case BOTH: | |
| 78 | return (p2->p_pid > p1->p_pid); /* tie - return highest pid */ | |
| 79 | } | |
| 00fe0339 MT |
80 | /* |
| 81 | * pick the one with the smallest sleep time | |
| 82 | */ | |
| 83 | if (p2->p_slptime > p1->p_slptime) | |
| 84 | return (0); | |
| 85 | if (p1->p_slptime > p2->p_slptime) | |
| 86 | return (1); | |
| 87 | /* | |
| 88 | * favor one sleeping in a non-interruptible sleep | |
| 89 | */ | |
| 90 | if (p1->p_flag&SSINTR && (p2->p_flag&SSINTR) == 0) | |
| 91 | return (1); | |
| 92 | if (p2->p_flag&SSINTR && (p1->p_flag&SSINTR) == 0) | |
| 93 | return (0); | |
| 94 | return(p2->p_pid > p1->p_pid); /* tie - return highest pid */ | |
| 95 | } |