usr.bin/w/proc_compare.c

   1 /*      $NetBSD: proc_compare.c,v 1.13 2004/02/13 11:36:24 wiz 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
  32 #include <sys/cdefs.h>
  33 #ifndef lint
  34 #if 0
  35 static char sccsid[] = "@(#)proc_compare.c      8.2 (Berkeley) 9/23/93";
  36 #else
  37 __RCSID("$NetBSD: proc_compare.c,v 1.13 2004/02/13 11:36:24 wiz Exp $");
  38 #endif
  39 #endif /* not lint */
  40
  41 #include <sys/param.h>
  42 #include <sys/time.h>
  43 #include <sys/sysctl.h>
  44
  45 #include "extern.h"
  46
  47 /*
  48  * Returns 1 if p2 is "better" than p1
  49  *
  50  * The algorithm for picking the "interesting" process is thus:
  51  *
  52  *      1) Only foreground processes are eligible - implied.
  53  *      2) Runnable processes are favored over anything else.  The runner
  54  *         with the highest CPU utilization is picked (p_pctcpu).  Ties are
  55  *         broken by picking the highest pid.
  56  *      3) The sleeper with the shortest sleep time is next.  With ties,
  57  *         we pick out just "short-term" sleepers (P_SINTR == 0).
  58  *      4) Further ties are broken by picking the highest pid.
  59  *
  60  * If you change this, be sure to consider making the change in the kernel
  61  * too (^T in kern/tty.c).
  62  *
  63  * TODO - consider whether pctcpu should be used.
  64  */
  65
  66 #define ISRUN(p)        (((p)->p_stat == LSRUN) || ((p)->p_stat == SIDL) || \
  67                          ((p)->p_stat == LSONPROC))
  68 #define TESTAB(a, b)    ((a)<<1 | (b))
  69 #define ONLYA   2
  70 #define ONLYB   1
  71 #define BOTH    3
  72
  73 int
  74 proc_compare(struct kinfo_proc2 *p1, struct kinfo_proc2 *p2)
  75 {
  76
  77         if (p1 == NULL)
  78                 return (1);
  79         /*
  80          * see if at least one of them is runnable
  81          */
  82         switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
  83         case ONLYA:
  84                 return (0);
  85         case ONLYB:
  86                 return (1);
  87         case BOTH:
  88                 /*
  89                  * tie - favor one with highest recent CPU utilization
  90                  */
  91                 if (p2->p_pctcpu > p1->p_pctcpu)
  92                         return (1);
  93                 if (p1->p_pctcpu > p2->p_pctcpu)
  94                         return (0);
  95                 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
  96         }
  97         /*
  98          * weed out zombies
  99          */
 100         switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) {
 101         case ONLYA:
 102                 return (1);
 103         case ONLYB:
 104                 return (0);
 105         case BOTH:
 106                 return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
 107         }
 108         /*
 109          * pick the one with the smallest sleep time
 110          */
 111         if (p2->p_slptime > p1->p_slptime)
 112                 return (0);
 113         if (p1->p_slptime > p2->p_slptime)
 114                 return (1);
 115         /*
 116          * favor one sleeping in a non-interruptible sleep
 117          */
 118         if (p1->p_flag & L_SINTR && (p2->p_flag & L_SINTR) == 0)
 119                 return (1);
 120         if (p2->p_flag & L_SINTR && (p1->p_flag & L_SINTR) == 0)
 121                 return (0);
 122         return (p2->p_pid > p1->p_pid);         /* tie - return highest pid */
 123 }