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    SubjectRe: scheduler nice 19 versus 'idle' behavior / static low-priority scheduling
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    On Fri, 2009-01-30 at 02:59 -0500, Nathanael Hoyle wrote:
    > On Fri, 2009-01-30 at 08:21 +0100, Jan Engelhardt wrote:
    > > On Friday 2009-01-30 07:40, Nathanael Hoyle wrote:
    > > >On Fri, 2009-01-30 at 07:16 +0100, Jan Engelhardt wrote:
    > > >
    > > >The one discussion I saw referencing SCHED_BATCH seemed to imply that it
    > > >was a non-standard kernel patch by Con Kolivas in one of his -ck
    > > >variants that never made it into mainline and is not being maintained.
    > > >Is this inaccurate?
    > >
    > > The presence of SCHED_BATCH in linux/sched.h tells me it is available
    > > (on the other hand, SCHED_ISO, also from -ck, is only listed as a comment.)
    > >
    >
    > Fair enough. I should have re-checked recent sources after your mention
    > rather than going on the old thread I found.
    >
    > > >I was unfamiliar with SCHED_IDLE. Having done a little Googling now, I
    > > >finally find reference to the man page for sched_setscheduler(2). This
    > > >appears that it is likely what I wanted.
    > > >
    > > >I think the information I had been able to find was somehwat out of
    > > >date.
    > >
    > > The manpage does say it, but if your local distro does not
    > > mention SCHED_BATCH/SCHED_IDLE, then that's a pretty sad distro.
    > >
    > > The doc in sched_setschedule seems complete to me as of man-pages 3.13.
    > >
    > > >Is there currently a standardized userspace tool to use to run a command
    > > >in order to alter its scheduling class? Obviously writing one would be
    > > >trivial, but didn't know if something like:
    > >
    > > man chrt
    >
    > The latest version of man chrt that I can find implies that it handles
    > SCHED_BATCH but not SCHED_IDLE. To that end, if anyone else is
    > interested, I have thrown together the above-suggested 'runidle' which
    > will invoke the passed command using the SCHED_IDLE scheduler; it's
    > nothing fancy.
    >
    > I am running foldingathome under it at the moment, and it seems to be
    > improving the situation somewhat, but I still need/want to test with
    > Mike's referenced patches.
    >

    <snipped old version, because of a fixed goof, and this has better
    formatting for mail client>


    #include <stdlib.h>
    #include <stdio.h>
    #include <unistd.h>
    #include <sched.h>
    #include <linux/sched.h>

    extern char **environ;

    int
    main(int argc, char **argv) {
    struct sched_param sp;
    sp.sched_priority = 0;

    if(argc<2) {
    perror("Must specify at least one argument: the path to " \
    "the program to execute. Additional arguments may be " \
    "specified which will be passed to the called program.");
    return EXIT_FAILURE;
    }

    if(sched_setscheduler(0, SCHED_IDLE, &sp) == -1) {
    perror("Failed to alter scheduling class!");
    return EXIT_FAILURE;
    }

    if(argc==2) {
    if(execve(argv[1], NULL, environ) == -1) {
    perror("Failed to execve target!");
    }
    } else {
    if(execve(argv[1], argv+1, environ) == -1) {
    perror("Failed to execve target!");
    }
    }

    /* should be unreachable */
    return EXIT_FAILURE;
    }

    > -Nathanael



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