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    SubjectRe: SCHED_IDLE documentation
    On Mon, Mar 3, 2008 at 10:31 AM, Arnd Bergmann <arnd@arndb.de> wrote:
    > On Monday 03 March 2008, Ingo Molnar wrote:
    > > > * What's the difference between SCHED_IDLE and SCHED_BATCH?
    > >
    > > SCHED_BATCH can still have nice levels from -20 to +19, it is a modified
    > > SCHED_OTHER/SCHED_NORMAL for "throughput oriented" workloads.
    > >
    > > SCHED_IDLE overrides the nice settings and it means a "super idle"
    > > workload.
    >
    > Does that mean that a SCHED_IDLE task still runs some of the time if
    > you have a CPU hog running on +19, or can any other process starve the
    > SCHED_IDLE task?

    Thanks. That was going to be my next question!

    I'm guessing that SCHED_IDLE doesn't get completely starved by a CPU
    hog running nice +19, but it would still be interesting to know:
    roughly how much of the CPU could the CPU_IDLE process expect to get
    in that case?

    > What happens if you have two SCHED_IDLE tasks on a single CPU, do they get
    > equal share, or will they just run as batch jobs?

    Also might be useful to add th e answer to this to the man page...

    Cheers,

    Michael


    --
    Michael Kerrisk
    Maintainer of the Linux man-pages project
    http://www.kernel.org/doc/man-pages/
    Want to report a man-pages bug? Look here:
    http://www.kernel.org/doc/man-pages/reporting_bugs.html


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