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Annotation of src/usr.bin/w/proc_compare.c, Revision 1.16

1.16    ! deraadt     1: /*     $OpenBSD: proc_compare.c,v 1.15 2015/01/16 06:40:14 deraadt Exp $       */
1.2       deraadt     2:
1.1       deraadt     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.
1.6       millert    15:  * 3. Neither the name of the University nor the names of its contributors
1.1       deraadt    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:
1.15      deraadt    32: #include <sys/param.h> /* MAXCOMLEN */
1.16    ! deraadt    33: #include <sys/signal.h>
1.13      millert    34: #include <sys/proc.h>
                     35: #include <sys/sysctl.h>
1.1       deraadt    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 (P_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:
1.9       markus     59: #define ISRUN(p)       (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL) || \
                     60:                         ((p)->p_stat == SONPROC))
1.1       deraadt    61: #define TESTAB(a, b)    ((a)<<1 | (b))
                     62: #define ONLYA   2
                     63: #define ONLYB   1
                     64: #define BOTH    3
                     65:
                     66: int
1.12      guenther   67: proc_compare(const struct kinfo_proc *p1, const struct kinfo_proc *p2)
1.1       deraadt    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->p_estcpu > p1->p_estcpu)
                     84:                        return (1);
                     85:                if (p1->p_estcpu > p2->p_estcpu)
                     86:                        return (0);
                     87:                return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
                     88:        }
                     89:        /*
1.10      deraadt    90:         * weed out zombies
1.1       deraadt    91:         */
1.14      guenther   92:        switch (TESTAB(p1->p_stat == SDEAD, p2->p_stat == SDEAD)) {
1.1       deraadt    93:        case ONLYA:
                     94:                return (1);
                     95:        case ONLYB:
                     96:                return (0);
                     97:        case BOTH:
                     98:                return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
                     99:        }
                    100:        /*
                    101:         * pick the one with the smallest sleep time
                    102:         */
                    103:        if (p2->p_slptime > p1->p_slptime)
                    104:                return (0);
                    105:        if (p1->p_slptime > p2->p_slptime)
                    106:                return (1);
                    107:        /*
                    108:         * favor one sleeping in a non-interruptible sleep
                    109:         */
                    110:        if (p1->p_flag & P_SINTR && (p2->p_flag & P_SINTR) == 0)
                    111:                return (1);
                    112:        if (p2->p_flag & P_SINTR && (p1->p_flag & P_SINTR) == 0)
                    113:                return (0);
                    114:        return (p2->p_pid > p1->p_pid);         /* tie - return highest pid */
                    115: }