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Diffstat (limited to 'usr.bin/w/proc_compare.c')
| -rw-r--r-- | usr.bin/w/proc_compare.c | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/usr.bin/w/proc_compare.c b/usr.bin/w/proc_compare.c new file mode 100644 index 0000000..e95359c --- /dev/null +++ b/usr.bin/w/proc_compare.c @@ -0,0 +1,120 @@ +/*- + * 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. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. 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. + */ + +#ifndef lint +static char sccsid[] = "@(#)proc_compare.c 8.2 (Berkeley) 9/23/93"; +#endif /* not lint */ + +#include <sys/param.h> +#include <sys/time.h> +#include <sys/proc.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)) +#define TESTAB(a, b) ((a)<<1 | (b)) +#define ONLYA 2 +#define ONLYB 1 +#define BOTH 3 + +int +proc_compare(p1, p2) + register struct proc *p1, *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 == SZOMB, p2->p_stat == SZOMB)) { + 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 */ +} |
