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      1 /*	$NetBSD: proc_compare.c,v 1.3 2020/01/06 13:21:18 skrll 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 #ifndef _STANDALONE
     32 # ifndef _KERNEL
     33 
     34 #  if HAVE_NBTOOL_CONFIG_H
     35 #   include "nbtool_config.h"
     36 #  endif
     37 
     38 #  include <sys/cdefs.h>
     39 #  if defined(LIBC_SCCS) && !defined(lint)
     40 __RCSID("$NetBSD: proc_compare.c,v 1.3 2020/01/06 13:21:18 skrll Exp $");
     41 #  endif
     42 
     43 #  include <sys/types.h>
     44 #  include <sys/inttypes.h>
     45 #  include <sys/sysctl.h>
     46 #  include <stdio.h>
     47 #  include <util.h>
     48 #  include <errno.h>
     49 #  define PROC		struct kinfo_proc2
     50 #  define LWP		struct kinfo_lwp
     51 #  define P_RTIME_SEC	p_rtime_sec
     52 #  define P_RTIME_USEC	p_rtime_usec
     53 # else
     54 #  include <sys/cdefs.h>
     55 __KERNEL_RCSID(0, "$NetBSD: proc_compare.c,v 1.3 2020/01/06 13:21:18 skrll Exp $");
     56 #  include <sys/param.h>
     57 #  include <sys/inttypes.h>
     58 #  include <sys/systm.h>
     59 #  include <sys/proc.h>
     60 #  include <sys/lwp.h>
     61 #  include <lib/libkern/libkern.h>
     62 #  define PROC		struct proc
     63 #  define LWP		struct lwp
     64 #  define P_RTIME_SEC	p_rtime.sec
     65 #  define P_RTIME_USEC	p_rtime.frac
     66 # endif
     67 /*
     68  * Returns 1 if p2 is "better" than p1
     69  *
     70  * The algorithm for picking the "interesting" process is thus:
     71  *
     72  *	1) Only foreground processes are eligible - implied.
     73  *	2) Runnable processes are favored over anything else.  The runner
     74  *	   with the highest CPU utilization is picked (l_pctcpu).  Ties are
     75  *	   broken by picking the highest pid.
     76  *	3) The sleeper with the shortest sleep time is next.  With ties,
     77  *	   we pick out just "short-term" sleepers (P_SINTR == 0).
     78  *	4) Further ties are broken by picking the one started last.
     79  *	5) Finally the one with the biggest pid wins, but that is nonsense
     80  *	   because of pid randomization.
     81  */
     82 #define	ISRUN(p)	((p)->p_nrlwps > 0)
     83 #define	TESTAB(a, b)	(((a) << 1) | (b))
     84 #define	ONLYA	2
     85 #define	ONLYB	1
     86 #define	BOTH	3
     87 
     88 int
     89 proc_compare(const PROC *p1, const LWP *l1, const PROC *p2, const LWP *l2)
     90 {
     91 	/*
     92  	 * weed out zombies
     93 	 */
     94 	switch (TESTAB(P_ZOMBIE(p1), P_ZOMBIE(p2))) {
     95 	case ONLYA:
     96 		return 1;
     97 	case ONLYB:
     98 		return 0;
     99 	case BOTH:
    100 		goto out;
    101 	}
    102 	/*
    103 	 * see if at least one of them is runnable
    104 	 */
    105 	switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
    106 	case ONLYA:
    107 		return 0;
    108 	case ONLYB:
    109 		return 1;
    110 	case BOTH:
    111 		/*
    112 		 * tie - favor one with highest recent CPU utilization
    113 		 */
    114 		if (l2->l_pctcpu > l1->l_pctcpu)
    115 			return 1;
    116 		goto out;
    117 	}
    118 	/*
    119 	 * pick the one with the smallest sleep time
    120 	 */
    121 	if (l1->l_slptime < l2->l_slptime)
    122 		return 0;
    123 	if (l2->l_slptime < l1->l_slptime)
    124 		return 1;
    125 
    126 	/*
    127 	 * favor one sleeping in a non-interruptible sleep
    128 	 */
    129 	if ((l1->l_flag & LW_SINTR) && (l2->l_flag & LW_SINTR) == 0)
    130 		return 0;
    131 	if ((l2->l_flag & LW_SINTR) && (l1->l_flag & LW_SINTR) == 0)
    132 		return 1;
    133 out:
    134 	/* tie, return the one with the smallest realtime */
    135 	if (p1->P_RTIME_SEC < p2->P_RTIME_SEC)
    136 		return 0;
    137 	if (p2->P_RTIME_SEC < p1->P_RTIME_SEC)
    138 		return 1;
    139 	if (p1->P_RTIME_USEC < p2->P_RTIME_USEC)
    140 		return 0;
    141 	if (p2->P_RTIME_USEC < p1->P_RTIME_USEC)
    142 		return 1;
    143 
    144 	return p2->p_pid > p1->p_pid;	/* Nonsense */
    145 }
    146 #endif /* STANDALONE */
    147