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    SubjectPoor performance during disk writes
    I have been witnessing what I believe to be poor performance from my
    computer ever since I have moved into the 2.4.x kernel versions. Combing
    through the unofficial archives of this mailing list reveals some others
    having similar problems, but I haven't seen any real resolution, or
    maybe their problems are completely different than mine.

    The problem simply is that whenever the computer does a big disk write,
    everything else is put on hold. Maybe this isn't a problem, but just the
    way it was written. I have tested this on a 2.2.x kernel and it also
    does it, but to a much lesser extent, to the point that I noticed the
    performance loss in the upgrade to a 2.4.x kernel and decided to
    investigate further.

    But also, I do not have any performance problems with disk reads.
    Programs can be loading up all they want and I am able to use my
    computer for other things during that time. It just seems to me (maybe
    I'm wrong) that the computer should be able to send small bits of data
    to the disk for writing during the off cycles and not affect the rest of
    the system (which is what I imagine it is doing for reads).

    To test, I've got a 142Meg file. I copy it around, makeing sure to copy
    from one disk to another. Of course the copy goes fine, because it does
    a cache (as I've been reading here), but eventually it needs to write
    out to disk (or when I do a sync) and here is where the computer hangs
    for a bit. If an mp3 is playing, it halts for 5 seconds at a time, mouse
    movement on the screen is VERY jerky, Gkrellm will stop updating for
    seconds and even just in console I can't type in stuff for a bit.

    I've been using hdparm to try and tweak hard disk access, but I'm not so
    sure this is the problem, and it's making me more confused about the
    entire situation. hdparm doesn't allow me to set using_dma, which it
    seems ought to be a necessity for getting a decent speed out of your
    hard drives (not that speed is the problem here), but despite that I
    still get a 51MB/s cache read speed in testing. Confusing, is the hard
    drive using (u)dma or not? Also, unmaskirq masks things a bit slower.

    So, the questions: Is there a way for me to stop this, some configure
    option? Is it a bug/performance issue that needs to be addressed in the
    kernel? Should I just go back to the 2.2.x kernel series and shutup

    I'm running 3 hard drives (30G Maxtor, 20G Seagate, and 2.1G Quantum
    Fireball) on an AMD k6-2 3dnow with a Gigabyte GA-5AX MOBO and the ALI
    Aladin V chipset.

    Thanks for your time and let me know if you need any more info/ output
    from dmesg or something.

    MACINTOSH = Machine Always Crashes If Not The Operating System Hangs
    "Life would be so much easier if we could just look at the source code."
    - Dave Olson

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