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. 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 }