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    SubjectRe: Schedule idle
    On Tue, Nov 10, 1998 at 07:28:39PM -0700, yodaiken@chelm.cs.nmt.edu wrote:
    > Decoupled enough for what? If you want RC5 jobs to not even use this tiny
    > amount of cpu while the batch jobs are running, why not
    >
    > start batch_job
    > signal rc5 process to shut down
    > if( !fork())
    > exec batch job
    > else wait()
    > restart rc5
    >
    >
    > Making the kernel do what can be done better by a shell script is not good.

    No, you just workaround a missing feature of the kernel: The ability to have
    things run only if nothing important (interactive jobs ...) can be done.

    With your shell script logic, you should start to try to figure out, what
    the names of the processes, which were meant for IDLE scheduling, and sent
    them SIGSTOP if you don't want to be disturbed. At the end you wake them
    again with SIGCONT.
    You are not even allowed to do that for other user's jobs on a multiuser
    machine.

    This is totally broken by design. You will have to guess which jobs were
    meant for IDLE scheduling. You will use some heuristic and guess, that all
    niced'19 jobs with names rc5des, cracker, ...

    It's the one who starts an IDLE job who should decide about a job being idle
    or not, not somebody who want to run a nice'd job (which is something
    completely different!) and wants not to compete with IDLE jobs.

    You need scheduler support for this, face it!

    Nobody claims, that this makes Linux a full RT system, which a simple
    scheduler patch won't do and which is probably not possible without changing
    some major design features of Linux.
    I do maintain, however, that this feature is very useful for a lot of
    people, most of them just using rc5des or cracker.

    Regards,
    --
    Kurt Garloff <K.Garloff@ping.de> (Dortmund, FRG)
    PGP key on http://student.physik.uni-dortmund.de/homepages/garloff
    Unix IS user friendly - it's just selective about who its friends are!

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