lkml.org 
[lkml]   [2004]   [Nov]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Priority Inheritance Test (Real-Time Preemption)

    * Esben Nielsen <simlo@phys.au.dk> wrote:

    > On Mon, 29 Nov 2004, Ingo Molnar wrote:
    >
    > > [...]
    > > To give you an extreme example: you cannot run OpenOffice.org with
    > > SCHED_FIFO prio 99 and expect it to have any sane deterministic latency
    > > bounds. The simpler the app, the easier it is to control latencies.
    >
    > No, but I want to have my RT-subsystem to be not affected even if the
    > users choose to run 1000 soffice.bin at SCHED_NORMAL!! [...]

    that is still the case, as long as it doesnt 'interact' with
    soffice.bin. Note that the same qualification holds for every hard-RT
    OS as well, with varying levels of 'interaction'. Interaction depends on
    what kind of synchronization the hard-RT task does, and depends on how
    the kernel itself implements various kernel features.

    > [...] The problem is that a raw spinlock is used to lock for a
    > iteration over a list which can be O(number of waiters * locking
    > depth) long. As long as we are in the kernel both is "controlled",
    > i.e. one can see the worst-case number in stress test and know it
    > can't get worse. *

    which list do you mean? Note that the pi_list depends on the number of
    _RT-tasks_, not on the number of SCHED_NORMAL tasks. So you can create
    an arbitrary number of SCHED_NORMAL tasks, they wont impact the overhead
    of mutexes!

    i very intentionally made it independent of nr-of-non-RT-tasks.

    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: 2005-03-22 14:08    [W:3.613 / U:1.192 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site