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    SubjectRe: [PATCH] sched: Rationalize sys_sched_rr_get_interval()
    On 13-10-2007 03:29, Peter Williams wrote:
    > Jarek Poplawski wrote:
    >> On 12-10-2007 00:23, Peter Williams wrote:
    >> ...
    >>> The reason I was going that route was for modularity (which helps
    >>> when adding plugsched patches). I'll submit a revised patch for
    >>> consideration.
    >> ...
    >>
    >> IMHO, it looks like modularity could suck here:
    >>
    >>> +static unsigned int default_timeslice_fair(struct task_struct *p)
    >>> +{
    >>> + return NS_TO_JIFFIES(sysctl_sched_min_granularity);
    >>> +}
    >>
    >> If it's needed for outside and sched_fair will use something else
    >> (to avoid double conversion) this could be misleading. Shouldn't
    >> this be kind of private and return something usable for the class
    >> mainly?
    >
    > This is supplying data for a system call not something for internal use
    > by the class. As far as the sched_fair class is concerned this is just
    > a (necessary - because it's need by a system call) diversion.

    So, now all is clear: this is the misleading case!

    >
    >> Why anything else than sched_fair should care about this?
    >
    > sched_fair doesn't care so if nothing else does why do we even have
    > sys_sched_rr_get_interval()? Is this whole function an anachronism that
    > can be expunged? I'm assuming that the reason it exists is that there
    > are user space programs that use this system call. Am I correct in this
    > assumption? Personally, I can't think of anything it would be useful
    > for other than satisfying curiosity.

    Since this is for some special aim (not default for most classes, at
    least not for sched_fair) I'd suggest to change names:
    default_timeslice_fair() and .default_timeslice to something like eg.:
    rr_timeslice_fair() and .rr_timeslice or rr_interval_fair() and
    .rr_interval (maybe with this "default" before_"rr_" if necessary).

    On the other hand man (2) sched_rr_get_interval mentions that:
    "The identified process should be running under the SCHED_RR
    scheduling policy".

    Also this place seems to say about something simpler:
    http://www.gnu.org/software/libc/manual/html_node/Basic-Scheduling-Functions.html

    So, I still doubt sched_fair's "notion" of timeslices should be
    necessary here.

    Sorry for too harsh words.

    Thanks,
    Jarek P.
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