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    SubjectRe: [PATCH 0/1] sched: fix typo in sched-rt-group.txt file
    From
    2009/5/20 GeunSik Lim <leemgs1@gmail.com>:
    >
    >
    > Dear Ingo,
    >
    >
    > I made 2 patch files again about static prioriy levels according to ingo's advice
    > and explanation. (Reference: http://marc.info/?t=124211992800003&r=1&w=2 archives. )
    >
    > Fix static priority related range and chart map(userspace/kernelspace) of ftrace.
    >   - about chart map of static priority in  ftrace.txt file
    >   - about static priority levels(range) in sched-rt-group.txt file
    >
    >
    > commit d6af702008117ca489a2f5476239d1688a517e98
    > Author: GeunSik,Lim <leemgs1@gmail.com>
    > Date:   Tue May 12 17:20:32 2009 +0900
    >
    >    sched: fix typo in sched-rt-group.txt file
    >
    >    Fix typo about static priority's range.
    >
    >    * Kernel Space priority 0(high) to 99(low)   --> User Space RT priority 99(high) to 1(low)
    >    * Kernel Space priority 100(high) to 139(low)--> User Space nice -20(high) to 19(low)
    >

    Ingo,
    I want to change some descriptions according to below discussion.

    before) * Kernel Space priority 0(high) to 99(low) --> User Space RT
    priority 99(high) to 1(low)
    after) * Kernel Space priority 0(high) to 98(low) --> User Space
    RT priority 99(high) to 1(low)

    I want to your advice and opinion about this changes.

    If I mistook, Please correct me.

    thks.



    Steven Rostedt:
    Shouldn't that be:
    Kernel priority: 0(high) to 98(low) ==> user RT priority 99(high) to 1(low)

    GeunSik Lim :
    Thank you for your opinion. I think about corrected expression for
    quick chart to map between kernel space and user space in ftrace .

    Steven Rostedt:
    100 items does not map to 99. Which begs the question, what can have
    internal kernel priority 99?

    GeunSik Lim :
    ok. Below example is about kernel (static) priority 99 that you said.
    please, refer
    to http://www.kernel.org/doc/man-pages/online/pages/man2/sched_setscheduler.2.html
    webpage.

    For processes scheduled under one of the normal scheduling policies
    (SCHED_OTHER, SCHED_IDLE, SCHED_BATCH), sched_priority is not used in
    scheduling decisions (it must be specified as 0).

    int main (int argc, char **argv)
    { int pidnumber, ret;
    struct sched_param p;
    p.sched_priority = 0; <------ Kernel (static) priority.
    if (argc != 2) {
    printf("usage: setbatch <pid>\n");
    exit(-1);
    }
    pidnumber = atol(argv[1]);
    /* 3 = Number of SCHED_BATCH Constant */
    ret = sched_setscheduler(pidnumber, 3, &p);
    if (ret) {
    printf("could not set pid %d to SCHED_BATCH: err %d.\n", pid, ret);
    return -1;
    }
    printf("pid %d is SCHED_BATCH from now on.\n", pid);
    return 0;
    }


    >
    >    Processes scheduled with SCHED_OTHER or SCHED_BATCH must be assigned
    >    the static priority 0. Processes scheduled under SCHED_FIFO or SCHED_RR
    >    can have a static priority in the range 1 to 99.
    >    (reference: $> man 2 sched_setscheduler)
    >
    >    Signed-off-by: GeunSik Lim <geunsik.lim@samsung.com>
    >
    > diff --git a/Documentation/scheduler/sched-rt-group.txt b/Documentation/scheduler/sched-rt-group.txt
    > index 5ba4d3f..1537146 100644
    > --- a/Documentation/scheduler/sched-rt-group.txt
    > +++ b/Documentation/scheduler/sched-rt-group.txt
    > @@ -169,7 +169,7 @@ get their allocated time.
    >
    >  Implementing SCHED_EDF might take a while to complete. Priority Inheritance is
    >  the biggest challenge as the current linux PI infrastructure is geared towards
    > -the limited static priority levels 0-139. With deadline scheduling you need to
    > +the limited static priority levels 0-99. With deadline scheduling you need to
    >  do deadline inheritance (since priority is inversely proportional to the
    >  deadline delta (deadline - now).
    >
    >
    >
    >
    > -----------------------------------------------
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    > Please read the FAQ at  http://www.tux.org/lkml/
    >
    > GeunSik Lim (ELS - OS Group - S/W Lab - SAIT - SAMSUNG)
    > e-Mail  :1) geunsik.lim@samsung.com
    >         2) leemgs@gmail.com , leemgs1@gmail.com
    > HomePage: http://intomail.dnip.net/invain/me/
    > -----------------------------------------------
    >



    --
    Regards,
    GeunSik Lim
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