127 lines
4.1 KiB
C
127 lines
4.1 KiB
C
/* $NetBSD: proc_compare.c,v 1.6 1996/06/07 01:39:27 thorpej Exp $ */
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/*-
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef lint
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#if 0
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static char sccsid[] = "@(#)proc_compare.c 8.2 (Berkeley) 9/23/93";
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#else
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static char rcsid[] = "$NetBSD: proc_compare.c,v 1.6 1996/06/07 01:39:27 thorpej Exp $";
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#endif
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#endif /* not lint */
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#include <sys/param.h>
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#include <sys/time.h>
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#include <sys/proc.h>
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#include "extern.h"
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/*
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* Returns 1 if p2 is "better" than p1
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*
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* The algorithm for picking the "interesting" process is thus:
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*
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* 1) Only foreground processes are eligible - implied.
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* 2) Runnable processes are favored over anything else. The runner
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* with the highest cpu utilization is picked (p_estcpu). Ties are
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* broken by picking the highest pid.
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* 3) The sleeper with the shortest sleep time is next. With ties,
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* we pick out just "short-term" sleepers (P_SINTR == 0).
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* 4) Further ties are broken by picking the highest pid.
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*
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* If you change this, be sure to consider making the change in the kernel
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* too (^T in kern/tty.c).
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*
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* TODO - consider whether pctcpu should be used.
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*/
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#define ISRUN(p) (((p)->p_stat == SRUN) || ((p)->p_stat == SIDL))
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#define TESTAB(a, b) ((a)<<1 | (b))
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#define ONLYA 2
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#define ONLYB 1
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#define BOTH 3
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int
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proc_compare(p1, p2)
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register struct proc *p1, *p2;
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{
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if (p1 == NULL)
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return (1);
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/*
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* see if at least one of them is runnable
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*/
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switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
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case ONLYA:
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return (0);
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case ONLYB:
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return (1);
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case BOTH:
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/*
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* tie - favor one with highest recent cpu utilization
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*/
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if (p2->p_estcpu > p1->p_estcpu)
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return (1);
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if (p1->p_estcpu > p2->p_estcpu)
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return (0);
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return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
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}
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/*
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* weed out zombies
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*/
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switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) {
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case ONLYA:
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return (1);
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case ONLYB:
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return (0);
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case BOTH:
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return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
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}
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/*
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* pick the one with the smallest sleep time
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*/
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if (p2->p_slptime > p1->p_slptime)
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return (0);
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if (p1->p_slptime > p2->p_slptime)
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return (1);
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/*
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* favor one sleeping in a non-interruptible sleep
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*/
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if (p1->p_flag & P_SINTR && (p2->p_flag & P_SINTR) == 0)
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return (1);
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if (p2->p_flag & P_SINTR && (p1->p_flag & P_SINTR) == 0)
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return (0);
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return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
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}
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