/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if 0
#ifndef lint
static char sccsid[] = "@(#)proc_compare.c 8.2 (Berkeley) 9/23/93";
#endif /* not lint */
#endif
#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/time.h>
#include <sys/user.h>
#include "extern.h"
/*
* Returns 1 if p2 is "better" than p1
*
* The algorithm for picking the "interesting" process is thus:
*
* 1) Only foreground processes are eligible - implied.
* 2) Runnable processes are favored over anything else. The runner
* with the highest cpu utilization is picked (p_estcpu). Ties are
* broken by picking the highest pid.
* 3) The sleeper with the shortest sleep time is next. With ties,
* we pick out just "short-term" sleepers (TDF_SINTR == 0).
* 4) Further ties are broken by picking the highest pid.
*
* If you change this, be sure to consider making the change in the kernel
* too (^T in kern/tty.c).
*
* TODO - consider whether pctcpu should be used.
*/
#define ISRUN(p) (((p)->ki_stat == SRUN) || ((p)->ki_stat == SIDL))
#define TESTAB(a, b) ((a)<<1 | (b))
#define ONLYA 2
#define ONLYB 1
#define BOTH 3
int
proc_compare(struct kinfo_proc *p1, struct kinfo_proc *p2)
{
if (p1 == NULL)
return (1);
/*
* see if at least one of them is runnable
*/
switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
case ONLYA:
return (0);
case ONLYB:
return (1);
case BOTH:
/*
* tie - favor one with highest recent cpu utilization
*/
if (p2->ki_estcpu > p1->ki_estcpu)
return (1);
if (p1->ki_estcpu > p2->ki_estcpu)
return (0);
return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */
}
/*
* weed out zombies
*/
switch (TESTAB(p1->ki_stat == SZOMB, p2->ki_stat == SZOMB)) {
case ONLYA:
return (1);
case ONLYB:
return (0);
case BOTH:
return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */
}
/*
* pick the one with the smallest sleep time
*/
if (p2->ki_slptime > p1->ki_slptime)
return (0);
if (p1->ki_slptime > p2->ki_slptime)
return (1);
/*
* favor one sleeping in a non-interruptible sleep
*/
if (p1->ki_tdflags & TDF_SINTR && (p2->ki_tdflags & TDF_SINTR) == 0)
return (1);
if (p2->ki_tdflags & TDF_SINTR && (p1->ki_tdflags & TDF_SINTR) == 0)
return (0);
return (p2->ki_pid > p1->ki_pid); /* tie - return highest pid */
}
plain