1 /* $OpenBSD: proc_compare.c,v 1.17 2022/02/22 17:35:01 deraadt 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. Neither the name of the University nor the names of its contributors 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 #include <sys/types.h> 33 #include <sys/signal.h> 34 #include <sys/proc.h> 35 #include <sys/sysctl.h> 36 #include <sys/time.h> 37 38 #include "extern.h" 39 40 /* 41 * Returns 1 if p2 is "better" than p1 42 * 43 * The algorithm for picking the "interesting" process is thus: 44 * 45 * 1) Only foreground processes are eligible - implied. 46 * 2) Runnable processes are favored over anything else. The runner 47 * with the highest cpu utilization is picked (p_estcpu). Ties are 48 * broken by picking the highest pid. 49 * 3) The sleeper with the shortest sleep time is next. With ties, 50 * we pick out just "short-term" sleepers (P_SINTR == 0). 51 * 4) Further ties are broken by picking the highest pid. 52 * 53 * If you change this, be sure to consider making the change in the kernel 54 * too (^T in kern/tty.c). 55 * 56 * TODO - consider whether pctcpu should be used. 57 */ 58 59 #define ISRUN(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL) || \ 60 ((p)->p_stat == SONPROC)) 61 #define TESTAB(a, b) ((a)<<1 | (b)) 62 #define ONLYA 2 63 #define ONLYB 1 64 #define BOTH 3 65 66 int 67 proc_compare(const struct kinfo_proc *p1, const struct kinfo_proc *p2) 68 { 69 if (p1 == NULL) 70 return (1); 71 /* 72 * see if at least one of them is runnable 73 */ 74 switch (TESTAB(ISRUN(p1), ISRUN(p2))) { 75 case ONLYA: 76 return (0); 77 case ONLYB: 78 return (1); 79 case BOTH: 80 /* 81 * tie - favor one with highest recent cpu utilization 82 */ 83 if (p2->p_estcpu > p1->p_estcpu) 84 return (1); 85 if (p1->p_estcpu > p2->p_estcpu) 86 return (0); 87 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */ 88 } 89 /* 90 * weed out zombies 91 */ 92 switch (TESTAB(p1->p_stat == SDEAD, p2->p_stat == SDEAD)) { 93 case ONLYA: 94 return (1); 95 case ONLYB: 96 return (0); 97 case BOTH: 98 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */ 99 } 100 /* 101 * pick the one with the smallest sleep time 102 */ 103 if (p2->p_slptime > p1->p_slptime) 104 return (0); 105 if (p1->p_slptime > p2->p_slptime) 106 return (1); 107 /* 108 * favor one sleeping in a non-interruptible sleep 109 */ 110 if (p1->p_flag & P_SINTR && (p2->p_flag & P_SINTR) == 0) 111 return (1); 112 if (p2->p_flag & P_SINTR && (p1->p_flag & P_SINTR) == 0) 113 return (0); 114 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */ 115 } 116