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    SubjectRe: How can we make page replacement smarter (was: swap-prefetch)
    Al Boldi wrote:
    > Chris Snook wrote:

    >> At best, reads can be read-ahead and cached, which is why
    >> sequential swap-in sucks less. On-demand reads are as expensive as I/O
    >> can get.
    >
    > Which means that it should be at least as fast as swap-out, even faster
    > because write to disk is usually slower than read on modern disks. But
    > linux currently shows a distinct 2x slowdown for sequential swap-in wrt
    > swap-out.

    That's because writes are faster than reads in moderate
    quantities.

    The disk caches writes, allowing the OS to write a whole
    bunch of data into the disk cache and the disk can optimize
    the IO a bit internally.

    The same optimization is not possible for reads.

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