1 /* $OpenBSD: proc_compare.c,v 1.4 2001/05/14 06:55:04 angelos 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. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #ifndef lint 37 #if 0 38 static char sccsid[] = "@(#)proc_compare.c 8.2 (Berkeley) 9/23/93"; 39 #else 40 static char *rcsid = "$OpenBSD: proc_compare.c,v 1.4 2001/05/14 06:55:04 angelos Exp $"; 41 #endif 42 #endif /* not lint */ 43 44 #include <sys/param.h> 45 #include <sys/time.h> 46 #include <sys/proc.h> 47 48 #include "extern.h" 49 50 /* 51 * Returns 1 if p2 is "better" than p1 52 * 53 * The algorithm for picking the "interesting" process is thus: 54 * 55 * 1) Only foreground processes are eligible - implied. 56 * 2) Runnable processes are favored over anything else. The runner 57 * with the highest cpu utilization is picked (p_estcpu). Ties are 58 * broken by picking the highest pid. 59 * 3) The sleeper with the shortest sleep time is next. With ties, 60 * we pick out just "short-term" sleepers (P_SINTR == 0). 61 * 4) Further ties are broken by picking the highest pid. 62 * 63 * If you change this, be sure to consider making the change in the kernel 64 * too (^T in kern/tty.c). 65 * 66 * TODO - consider whether pctcpu should be used. 67 */ 68 69 #define ISRUN(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL)) 70 #define TESTAB(a, b) ((a)<<1 | (b)) 71 #define ONLYA 2 72 #define ONLYB 1 73 #define BOTH 3 74 75 int 76 proc_compare(p1, p2) 77 register struct proc *p1, *p2; 78 { 79 if (p1 == NULL) 80 return (1); 81 /* 82 * see if at least one of them is runnable 83 */ 84 switch (TESTAB(ISRUN(p1), ISRUN(p2))) { 85 case ONLYA: 86 return (0); 87 case ONLYB: 88 return (1); 89 case BOTH: 90 /* 91 * tie - favor one with highest recent cpu utilization 92 */ 93 if (p2->p_estcpu > p1->p_estcpu) 94 return (1); 95 if (p1->p_estcpu > p2->p_estcpu) 96 return (0); 97 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */ 98 } 99 /* 100 * weed out zombies 101 */ 102 switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) { 103 case ONLYA: 104 return (1); 105 case ONLYB: 106 return (0); 107 case BOTH: 108 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */ 109 } 110 /* 111 * pick the one with the smallest sleep time 112 */ 113 if (p2->p_slptime > p1->p_slptime) 114 return (0); 115 if (p1->p_slptime > p2->p_slptime) 116 return (1); 117 /* 118 * favor one sleeping in a non-interruptible sleep 119 */ 120 if (p1->p_flag & P_SINTR && (p2->p_flag & P_SINTR) == 0) 121 return (1); 122 if (p2->p_flag & P_SINTR && (p1->p_flag & P_SINTR) == 0) 123 return (0); 124 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */ 125 } 126