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    SubjectRe: O_DIRECT question
    Michael Tokarev wrote:
    > After all the explanations, I still don't see anything wrong with the
    > interface itself. O_DIRECT isn't "different semantics" - we're still
    > writing and reading some data. Yes, O_DIRECT and non-O_DIRECT usages
    > somewhat contradicts with each other, but there are other ways to make
    > the two happy, instead of introducing alot of stupid, complex, and racy
    > code all over.

    By the way. I just ran - for fun - a read test of a raid array.

    Reading blocks of size 512kbytes, starting at random places on a 400Gb
    array, doing 64threads.

    O_DIRECT: 336.73 MB/sec.
    !O_DIRECT: 146.00 MB/sec.

    Quite a... difference here.

    Using posix_fadvice() does not improve it.

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      Last update: 2007-01-12 22:23    [W:0.028 / U:5.848 seconds]
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