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    SubjectRe: (disk/cpu) kernel performance problem
    On Mon, 26 Jul 1999, Gerald Aigner wrote:

    > While optimizing the program I discovered that disk I/O
    > performance in Linux could be improved substantially. In
    > particular, there are two main problems:
    >
    > 1) The kernel copies data many times before it ends up in user
    > space.


    I'm very sorry, but you seem to be too late. This problem is
    (at least partially) fixed in the newer 2.3 kernels...

    > 2) Using mmap doesn't help because it serializes I/O within a single
    > process (you can't read simultaneously from two disks).

    A single process uses a single thread of control, and yes,
    we do readahead over RAID0 sets...

    If you want to do true async I/O, you can just use the
    interface glibc gives you to do that.

    Rik -- Open Source: you deserve to be in control of your data.
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