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    SubjectRe: 2.6.0-test9 - poor swap performance on low end machines
    On Tue, 09 Dec 2003 11:04:49 -0500, Rik van Riel wrote:
    > > The classic strategies based on these criteria work for transaction and
    > > batch systems. They are all but useless, though, for a workstation and
    > > even most modern servers, due to assumptions that are incorrect today
    > > (remember all the degrees of freedom a scheduler had 30 years ago)
    > > and additional factors that only became crucial in the past few decades
    > > (latency again).
    >
    > Don't forget that computers have gotten a lot slower
    > over the years ;)
    >
    > Swapping out a 64kB process to a disk that does 180kB/s
    > is a lot faster than swapping out a 100MB process to a
    > disk that does 50MB/s ...
    >
    > Once you figure in seek times, the picture looks even
    > worse.

    Exactly -- I did mention the growing access time gap between RAM and
    disks in an earlier message. Yes, there are quite a few developments in
    hardware and in the way we use computers (interactive, Client/Server,
    dedicated machines, etc.) that made thrashing pretty much unsolvable
    at an OS level. Fortunately, fixing it in hardware by adding RAM works
    for most.

    What we _can_ do in software, though, is prevent thrashing as long as
    possible. Comparing 2.4 and 2.6 shows that a kernel can still make a
    significant difference with smart pageout algorithms, I/O scheduling etc.
    But you won't get much help with that from ancient papers.

    Roger
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