126 lines
3.9 KiB
C
126 lines
3.9 KiB
C
/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* 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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/*static char sccsid[] = "from: @(#)proc_compare.c 5.4 (Berkeley) 2/7/91";*/
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static char rcsid[] = "$Id: proc_compare.c,v 1.2 1993/08/01 18:03:16 mycroft Exp $";
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#endif /* not lint */
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/*
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* Returns 1 if p2 is more active than p1
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*
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* The algorithm for picking the "more active" process is thus:
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*
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* 1) Runnable processes are favored over anything
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* else. The runner with the highest cpu
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* utilization is picked (p_cpu). Ties are
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* broken by picking the highest pid.
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* 2) Next, the sleeper with the shortest sleep
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* time is favored. With ties, we pick out
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* just short-term sleepers (p_pri <= PZERO).
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* Further ties are broken by picking the highest
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* pid.
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*
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* NOTE - if you change this, be sure to consider making
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* the change in the kernel 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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*/
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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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#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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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_cpu > p1->p_cpu)
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return (1);
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if (p1->p_cpu > p2->p_cpu)
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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&SSINTR && (p2->p_flag&SSINTR) == 0)
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return (1);
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if (p2->p_flag&SSINTR && (p1->p_flag&SSINTR) == 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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