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    Subject[patch] Re: scheduling priorities

    On Fri, 15 Jan 1999, Gabriel Paubert wrote:

    > It furiously looks like an off by one error (or an < versus <=
    > comparison, or a postfix versus prefix increment or decrement)
    > which would give actually 2 and 21 slices rather than 1 and 20:
    >
    > 2/23 ~= 8.7 %
    > 21/23 ~= 91.3 %

    yes, the reason is that we do not reschedule when we reach
    current->counter == 0, but only when current->counter <= 0:

    p->counter -= ticks;
    if (p->counter < 0) {
    p->counter = 0;
    p->need_resched = 1;

    this is not a problem i think, according comments should be updated:

    --- linux/kernel/sched.c.orig3 Fri Jan 15 15:45:40 1999
    +++ linux/kernel/sched.c Fri Jan 15 15:46:12 1999
    @@ -1551,7 +1551,7 @@
    * do a "normalization" of the priority (traditionally
    * Unix nice values are -20 to 20; Linux doesn't really
    * use that kind of thing, but uses the length of the
    - * timeslice instead (default 150 ms). The rounding is
    + * timeslice instead (default 210 ms). The rounding is
    * why we want to avoid negative values.
    */
    newprio = (newprio * DEF_PRIORITY + 10) / 20;
    --- linux/include/linux/sched.h.orig3 Fri Jan 15 15:44:59 1999
    +++ linux/include/linux/sched.h Fri Jan 15 15:45:16 1999
    @@ -332,7 +332,7 @@
    */
    #define _STK_LIM (8*1024*1024)

    -#define DEF_PRIORITY (20*HZ/100) /* 200 ms time slices */
    +#define DEF_PRIORITY (20*HZ/100) /* 210 ms time slices */

    /*
    * INIT_TASK is used to set up the first task table, touch at



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