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/* $OpenBSD: proc_compare.c,v 1.17 2022/02/22 17:35:01 deraadt Exp $ */
/*-
* 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.
*/
#include <sys/types.h>
#include <sys/signal.h>
#include <sys/proc.h>
#include <sys/sysctl.h>
#include <sys/time.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 (P_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)->p_stat == SRUN) || ((p)->p_stat == SIDL) || \
((p)->p_stat == SONPROC))
#define TESTAB(a, b) ((a)<<1 | (b))
#define ONLYA 2
#define ONLYB 1
#define BOTH 3
int
proc_compare(const struct kinfo_proc *p1, const 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->p_estcpu > p1->p_estcpu)
return (1);
if (p1->p_estcpu > p2->p_estcpu)
return (0);
return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
}
/*
* weed out zombies
*/
switch (TESTAB(p1->p_stat == SDEAD, p2->p_stat == SDEAD)) {
case ONLYA:
return (1);
case ONLYB:
return (0);
case BOTH:
return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
}
/*
* pick the one with the smallest sleep time
*/
if (p2->p_slptime > p1->p_slptime)
return (0);
if (p1->p_slptime > p2->p_slptime)
return (1);
/*
* favor one sleeping in a non-interruptible sleep
*/
if (p1->p_flag & P_SINTR && (p2->p_flag & P_SINTR) == 0)
return (1);
if (p2->p_flag & P_SINTR && (p1->p_flag & P_SINTR) == 0)
return (0);
return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
}
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