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 #include <sys/param.h> 33 #include <sys/proc.h> 34 #include <sys/time.h> 35 #include <sys/user.h> 36 37 #include "extern.h" 38 39 /* 40 * Returns 1 if p2 is "better" than p1 41 * 42 * The algorithm for picking the "interesting" process is thus: 43 * 44 * 1) Only foreground processes are eligible - implied. 45 * 2) Runnable processes are favored over anything else. The runner 46 * with the highest cpu utilization is picked (p_estcpu). Ties are 47 * broken by picking the highest pid. 48 * 3) The sleeper with the shortest sleep time is next. With ties, 49 * we pick out just "short-term" sleepers (TDF_SINTR == 0). 50 * 4) Further ties are broken by picking the highest pid. 51 * 52 * If you change this, be sure to consider making the change in the kernel 53 * too (^T in kern/tty.c). 54 * 55 * TODO - consider whether pctcpu should be used. 56 */ 57 58 #define ISRUN(p) (((p)->ki_stat == SRUN) || ((p)->ki_stat == SIDL)) 59 #define TESTAB(a, b) ((a)<<1 | (b)) 60 #define ONLYA 2 61 #define ONLYB 1 62 #define BOTH 3 63 64 int 65 proc_compare(struct kinfo_proc *p1, struct kinfo_proc *p2) 66 { 67 68 if (p1 == NULL) 69 return (1); 70 /* 71 * see if at least one of them is runnable 72 */ 73 switch (TESTAB(ISRUN(p1), ISRUN(p2))) { 74 case ONLYA: 75 return (0); 76 case ONLYB: 77 return (1); 78 case BOTH: 79 /* 80 * tie - favor one with highest recent cpu utilization 81 */ 82 if (p2->ki_estcpu > p1->ki_estcpu) 83 return (1); 84 if (p1->ki_estcpu > p2->ki_estcpu) 85 return (0); 86 return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */ 87 } 88 /* 89 * weed out zombies 90 */ 91 switch (TESTAB(p1->ki_stat == SZOMB, p2->ki_stat == SZOMB)) { 92 case ONLYA: 93 return (1); 94 case ONLYB: 95 return (0); 96 case BOTH: 97 return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */ 98 } 99 /* 100 * pick the one with the smallest sleep time 101 */ 102 if (p2->ki_slptime > p1->ki_slptime) 103 return (0); 104 if (p1->ki_slptime > p2->ki_slptime) 105 return (1); 106 /* 107 * favor one sleeping in a non-interruptible sleep 108 */ 109 if (p1->ki_tdflags & TDF_SINTR && (p2->ki_tdflags & TDF_SINTR) == 0) 110 return (1); 111 if (p2->ki_tdflags & TDF_SINTR && (p1->ki_tdflags & TDF_SINTR) == 0) 112 return (0); 113 return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */ 114 } 115