usr.bin/w/proc_compare.c

   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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)proc_compare.c   8.2 (Berkeley) 9/23/93
  34  *
  35  * $DragonFly: src/usr.bin/w/proc_compare.c,v 1.9 2007/02/18 16:15:24 corecode Exp $
  36  */
  37
  38 #include <sys/param.h>
  39 #include <sys/time.h>
  40 #include <sys/user.h>
  41
  42 #include "extern.h"
  43
  44 /*
  45  * Returns 1 if p2 is "better" than p1
  46  *
  47  * The algorithm for picking the "interesting" process is thus:
  48  *
  49  *      1) Only foreground processes are eligible - implied.
  50  *      2) Runnable processes are favored over anything else.  The runner
  51  *         with the highest cpu utilization is picked (p_estcpu).  Ties are
  52  *         broken by picking the highest pid.
  53  *      3) The sleeper with the shortest sleep time is next.  With ties,
  54  *         we pick out just "short-term" sleepers (LWP_SINTR == 0).
  55  *      4) Further ties are broken by picking the highest pid.
  56  *
  57  * If you change this, be sure to consider making the change in the kernel
  58  * too (^T in kern/tty.c).
  59  *
  60  * TODO - consider whether pctcpu should be used.
  61  */
  62
  63 #define ISRUN(p)        ((p)->kp_lwp.kl_stat == LSRUN)
  64 #define TESTAB(a, b)    ((a)<<1 | (b))
  65 #define ONLYA   2
  66 #define ONLYB   1
  67 #define BOTH    3
  68
  69 int
  70 proc_compare(struct kinfo_proc *p1, struct kinfo_proc *p2)
  71 {
  72
  73         if (p1 == NULL)
  74                 return (1);
  75         /*
  76          * see if at least one of them is runnable
  77          */
  78         switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
  79         case ONLYA:
  80                 return (0);
  81         case ONLYB:
  82                 return (1);
  83         case BOTH:
  84                 /*
  85                  * tie - favor one with highest recent cpu utilization
  86                  */
  87                 if (p2->kp_lwp.kl_estcpu > p1->kp_lwp.kl_estcpu)
  88                         return (1);
  89                 if (p1->kp_lwp.kl_estcpu > p2->kp_lwp.kl_estcpu)
  90                         return (0);
  91                 return (p2->kp_pid > p1->kp_pid);       /* tie - return highest pid */
  92         }
  93         /*
  94          * weed out zombies
  95          */
  96         switch (TESTAB(p1->kp_stat == SZOMB, p2->kp_stat == SZOMB)) {
  97         case ONLYA:
  98                 return (1);
  99         case ONLYB:
 100                 return (0);
 101         case BOTH:
 102                 return (p2->kp_pid > p1->kp_pid); /* tie - return highest pid */
 103         }
 104         /*
 105          * pick the one with the smallest sleep time
 106          */
 107         if (p2->kp_lwp.kl_slptime > p1->kp_lwp.kl_slptime)
 108                 return (0);
 109         if (p1->kp_lwp.kl_slptime > p2->kp_lwp.kl_slptime)
 110                 return (1);
 111         /*
 112          * favor one sleeping in a non-interruptible sleep
 113          */
 114         if (p1->kp_lwp.kl_flags & LWP_SINTR && (p2->kp_lwp.kl_flags & LWP_SINTR) == 0)
 115                 return (1);
 116         if (p2->kp_lwp.kl_flags & LWP_SINTR && (p1->kp_lwp.kl_flags & LWP_SINTR) == 0)
 117                 return (0);
 118         return (p2->kp_pid > p1->kp_pid);               /* tie - return highest pid */
 119 }