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 #endif 34 35 #include <sys/cdefs.h> 36 #include <sys/param.h> 37 #include <sys/proc.h> 38 #include <sys/time.h> 39 #include <sys/user.h> 40 41 #include "extern.h" 42 43 /* 44 * Returns 1 if p2 is "better" than p1 45 * 46 * The algorithm for picking the "interesting" process is thus: 47 * 48 * 1) Only foreground processes are eligible - implied. 49 * 2) Runnable processes are favored over anything else. The runner 50 * with the highest cpu utilization is picked (p_estcpu). Ties are 51 * broken by picking the highest pid. 52 * 3) The sleeper with the shortest sleep time is next. With ties, 53 * we pick out just "short-term" sleepers (TDF_SINTR == 0). 54 * 4) Further ties are broken by picking the highest pid. 55 * 56 * If you change this, be sure to consider making the change in the kernel 57 * too (^T in kern/tty.c). 58 * 59 * TODO - consider whether pctcpu should be used. 60 */ 61 62 #define ISRUN(p) (((p)->ki_stat == SRUN) || ((p)->ki_stat == SIDL)) 63 #define TESTAB(a, b) ((a)<<1 | (b)) 64 #define ONLYA 2 65 #define ONLYB 1 66 #define BOTH 3 67 68 int 69 proc_compare(struct kinfo_proc *p1, struct kinfo_proc *p2) 70 { 71 72 if (p1 == NULL) 73 return (1); 74 /* 75 * see if at least one of them is runnable 76 */ 77 switch (TESTAB(ISRUN(p1), ISRUN(p2))) { 78 case ONLYA: 79 return (0); 80 case ONLYB: 81 return (1); 82 case BOTH: 83 /* 84 * tie - favor one with highest recent cpu utilization 85 */ 86 if (p2->ki_estcpu > p1->ki_estcpu) 87 return (1); 88 if (p1->ki_estcpu > p2->ki_estcpu) 89 return (0); 90 return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */ 91 } 92 /* 93 * weed out zombies 94 */ 95 switch (TESTAB(p1->ki_stat == SZOMB, p2->ki_stat == SZOMB)) { 96 case ONLYA: 97 return (1); 98 case ONLYB: 99 return (0); 100 case BOTH: 101 return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */ 102 } 103 /* 104 * pick the one with the smallest sleep time 105 */ 106 if (p2->ki_slptime > p1->ki_slptime) 107 return (0); 108 if (p1->ki_slptime > p2->ki_slptime) 109 return (1); 110 /* 111 * favor one sleeping in a non-interruptible sleep 112 */ 113 if (p1->ki_tdflags & TDF_SINTR && (p2->ki_tdflags & TDF_SINTR) == 0) 114 return (1); 115 if (p2->ki_tdflags & TDF_SINTR && (p1->ki_tdflags & TDF_SINTR) == 0) 116 return (0); 117 return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */ 118 } 119