lkml.org 
[lkml]   [2007]   [Aug]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: CFS review

    * Linus Torvalds <torvalds@linux-foundation.org> wrote:

    > On Tue, 28 Aug 2007, Al Boldi wrote:
    > >
    > > I like your analysis, but how do you explain that these stalls
    > > vanish when __update_curr is disabled?
    >
    > It's entirely possible that what happens is that the X scheduling is
    > just a slightly unstable system - which effectively would turn a small
    > scheduling difference into a *huge* visible difference.

    i think it's because disabling __update_curr() in essence removes the
    ability of scheduler to preempt tasks - that hack in essence results in
    a non-scheduler. Hence the gears + X pair of tasks becomes a synchronous
    pair of tasks in essence - and thus gears cannot "overload" X.

    Normally gears + X is an asynchronous pair of tasks, with gears (or
    xperf, or devel versions of firefox, etc.) not being throttled at all
    and thus being able to overload/spam the X server with requests. (And we
    generally want to _reward_ asynchronity and want to allow tasks to
    overlap each other and we want each task to go as fast and as parallel
    as it can.)

    Eventually X's built-in "bad, abusive client" throttling code kicks in,
    which, AFAIK is pretty crude and might yield to such artifacts. But ...
    it would be nice for an X person to confirm - and in any case i'll try
    Al's workload - i thought i had a reproducer but i barked up the wrong
    tree :-) My laptop doesnt run with the vesa driver, so i have no easy
    reproducer for now.

    ( also, it would be nice if Al could try rc4 plus my latest scheduler
    tree as well - just on the odd chance that something got fixed
    meanwhile. In particular Mike's sleeper-bonus-limit fix could be
    related. )

    Ingo
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-08-28 18:49    [W:0.048 / U:30.384 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site