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    SubjectRe: 2.1.99 is less rusty
    Date
    According to linker@nightshade.ml.org:
    >
    > Well.. Depending on your test new kernels might always be 'slower' after
    > the find.. This is still 'too slow' but the 2.0 performance might no have
    > been as ideal as you think.

    Did I say 2.0 performance was ideal? If so, I didn't mean to and I
    didn't mean to imply that I thought so.

    > 2.0 performed better becase some disk blocks got cached.
    > 2.1 performes worse because the dcache gets plumped but not slimmed.

    Maybe, I don't claim to understand why the rusting effect occurs...

    > Your benchmark might not benifit from the dcache because it might not
    > touch enough files for it to matter.
    >
    > So even if the dcache was clearing out right you'd still lose a little
    > time for the 'clearing'.. and your benchmark might not benifit from the
    > dcache leading to a net slowdown.. :)

    Hmm, I think that I'd like to avoid the use of the term "benchmark"
    here... Perhaps I should re-iterate what the problem is: in later
    kernels on a "low" memory (all relative.. my first personal computer
    had 4 kbyte of RAM) machine there is an effect where more and more
    swapping occurs as one uses the system. Thus after a while the system
    is very sluggish. I haven't discovered any way to reverse this
    process apart from re-booting. My little test script is claimed to do
    nothing more than accelerate this process (relative to "normal" use)
    and to provide a rough metric.

    I don't know what causes the effect. People have suggested it is due
    to either memory fragmentation or cache memory not being freed. I
    have looked at the stuff available via /proc and SysRq but it didn't
    appear to particularly support either hypothesis.

    Linus has announced that the 2.1.xx series will end soon and this is
    one problem which I think really should not be knowingly allowed to be
    a feature of 2.2.

    I don't have the time at the moment to get stuck into solving the
    problem myself so I have to hope that the people who have designed the
    stuff will fix it (if they feel so inclined and can find the time...).


    Cheers,
    Bill

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