1 /*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)proc_compare.c 8.2 (Berkeley) 9/23/93 30 * 31 * $DragonFly: src/usr.bin/w/proc_compare.c,v 1.9 2007/02/18 16:15:24 corecode Exp $ 32 */ 33 34 #include <sys/user.h> 35 #include <sys/param.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 (LWP_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)->kp_lwp.kl_stat == LSRUN) 60 #define TESTAB(a, b) ((a)<<1 | (b)) 61 #define ONLYA 2 62 #define ONLYB 1 63 #define BOTH 3 64 65 int 66 proc_compare(struct kinfo_proc *p1, struct kinfo_proc *p2) 67 { 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->kp_lwp.kl_estcpu > p1->kp_lwp.kl_estcpu) 84 return (1); 85 if (p1->kp_lwp.kl_estcpu > p2->kp_lwp.kl_estcpu) 86 return (0); 87 return (p2->kp_pid > p1->kp_pid); /* tie - return highest pid */ 88 } 89 /* 90 * weed out zombies 91 */ 92 switch (TESTAB(p1->kp_stat == SZOMB, p2->kp_stat == SZOMB)) { 93 case ONLYA: 94 return (1); 95 case ONLYB: 96 return (0); 97 case BOTH: 98 return (p2->kp_pid > p1->kp_pid); /* tie - return highest pid */ 99 } 100 /* 101 * pick the one with the smallest sleep time 102 */ 103 if (p2->kp_lwp.kl_slptime > p1->kp_lwp.kl_slptime) 104 return (0); 105 if (p1->kp_lwp.kl_slptime > p2->kp_lwp.kl_slptime) 106 return (1); 107 /* 108 * favor one sleeping in a non-interruptible sleep 109 */ 110 if (p1->kp_lwp.kl_flags & LWP_SINTR && (p2->kp_lwp.kl_flags & LWP_SINTR) == 0) 111 return (1); 112 if (p2->kp_lwp.kl_flags & LWP_SINTR && (p1->kp_lwp.kl_flags & LWP_SINTR) == 0) 113 return (0); 114 return (p2->kp_pid > p1->kp_pid); /* tie - return highest pid */ 115 } 116