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    SubjectRe: Machine's high load when HIGHMEM is enabled

    First of all - thanks to these people, who responded
    to my question.

    I have some news...

    I've tried kernels:
    2.4.19 - the same result
    2.5.44 - the same result
    2.5.45 - the same result

    If I take 1 Gb of memory away, then computer works
    much better, faster (something like without enabled
    HIGHMEM at all).
    The same effect takes place if I say mem=1024M while
    physically box has 2Gb of RAM - everything is fine!
    But if I start HIGHMEM enabled kernel on this box (2Gb
    RAM), then it works too slowly...

    The questions are:
    1. is there anyone on the list, who has the same or
    near configuration ? (main is that the box has >=2Gb
    of RAM)
    2. do you experience the same problems ?
    3. maybe it's not a problem at all?!? I mean maybe
    linux kernel works this way with such amount of memory
    and there is no problem with that?
    4. the case I've described =

    and finally, if this could be solved - please tell,
    how should I set up the kernel/kernel settings to get
    appropriate results in performance ?

    Thank you.

    --- Brian Gerst <> wrote:
    > 2.4 can only do I/O to and from lowmem. This means
    > highmem pages have
    > to use bounce buffers in lowmem, and th edata is
    > copied to/from highmem
    > which is causing the cpu load. This has been
    > corrected in 2.5, which
    > can do I/O to any page the device can DMA from.

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