1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 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 #if 0 33 #ifndef lint 34 static char sccsid[] = "@(#)proc_compare.c 8.2 (Berkeley) 9/23/93"; 35 #endif /* not lint */ 36 #endif 37 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include <sys/param.h> 42 #include <sys/proc.h> 43 #include <sys/time.h> 44 #include <sys/user.h> 45 46 #include "extern.h" 47 48 /* 49 * Returns 1 if p2 is "better" than p1 50 * 51 * The algorithm for picking the "interesting" process is thus: 52 * 53 * 1) Only foreground processes are eligible - implied. 54 * 2) Runnable processes are favored over anything else. The runner 55 * with the highest cpu utilization is picked (p_estcpu). Ties are 56 * broken by picking the highest pid. 57 * 3) The sleeper with the shortest sleep time is next. With ties, 58 * we pick out just "short-term" sleepers (TDF_SINTR == 0). 59 * 4) Further ties are broken by picking the highest pid. 60 * 61 * If you change this, be sure to consider making the change in the kernel 62 * too (^T in kern/tty.c). 63 * 64 * TODO - consider whether pctcpu should be used. 65 */ 66 67 #define ISRUN(p) (((p)->ki_stat == SRUN) || ((p)->ki_stat == SIDL)) 68 #define TESTAB(a, b) ((a)<<1 | (b)) 69 #define ONLYA 2 70 #define ONLYB 1 71 #define BOTH 3 72 73 int 74 proc_compare(struct kinfo_proc *p1, struct kinfo_proc *p2) 75 { 76 77 if (p1 == NULL) 78 return (1); 79 /* 80 * see if at least one of them is runnable 81 */ 82 switch (TESTAB(ISRUN(p1), ISRUN(p2))) { 83 case ONLYA: 84 return (0); 85 case ONLYB: 86 return (1); 87 case BOTH: 88 /* 89 * tie - favor one with highest recent cpu utilization 90 */ 91 if (p2->ki_estcpu > p1->ki_estcpu) 92 return (1); 93 if (p1->ki_estcpu > p2->ki_estcpu) 94 return (0); 95 return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */ 96 } 97 /* 98 * weed out zombies 99 */ 100 switch (TESTAB(p1->ki_stat == SZOMB, p2->ki_stat == SZOMB)) { 101 case ONLYA: 102 return (1); 103 case ONLYB: 104 return (0); 105 case BOTH: 106 return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */ 107 } 108 /* 109 * pick the one with the smallest sleep time 110 */ 111 if (p2->ki_slptime > p1->ki_slptime) 112 return (0); 113 if (p1->ki_slptime > p2->ki_slptime) 114 return (1); 115 /* 116 * favor one sleeping in a non-interruptible sleep 117 */ 118 if (p1->ki_tdflags & TDF_SINTR && (p2->ki_tdflags & TDF_SINTR) == 0) 119 return (1); 120 if (p2->ki_tdflags & TDF_SINTR && (p1->ki_tdflags & TDF_SINTR) == 0) 121 return (0); 122 return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */ 123 } 124