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    SubjectRe: Real-time problem due to IO congestion.

    I see.
    The program which I tested is just sample, and I wanted to know the
    phenomena is spec or bug.
    I also understand that this problem is spec, and need to apply some
    buffering to such applications.

    Thank you.

    Andrew Morton wrote:
    > Takashi Ikebe <ikebe.takashi@lab.ntt.co.jp> wrote:
    >
    >>There are 2 type processes in test environment.
    >> 1. The real-time needed process (run on with high static priority)
    >> The process wake up every 10ms, and wake up, write some log (the
    >> test case is current CPU clock via tsc) to the file.
    >>
    >> 2. The process which make IO load
    >> The process have large memory size, and kill the process with dumping.
    >> The process's memory area exceeds 70% of whole physical
    >> RAM.(Actually 1.5GB memory area while whole RAM is 2GB)
    >>
    >> Whenever during dumping, the real-time needed process sometimes stop for
    >> long time during write system call. (sometimes exceeds 1000ms)
    >
    >
    > The writeback code does attempt to give some preference to realtime tasks
    > (in get_dirty_limits()), but it can only work up to a point.
    >
    > Frankly, your application is poorly designed. If you want sub-10ms
    > responsiveness you shouldn't be doing disk I/O. The realtime task should
    > hand the data off to a non-realtime task for writeout, with suitable
    > amounts of buffering in between.

    --
    Takashi Ikebe
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