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    SubjectRe: O_DIRECT question
    Date
    Denis Vlasenko wrote:
    > On Thursday 25 January 2007 21:45, Michael Tokarev wrote:
    >> Phillip Susi wrote:
    >>> Denis Vlasenko wrote:
    >>>> You mean "You can use aio_write" ?
    >>> Exactly. You generally don't use O_DIRECT without aio. Combining the
    >>> two is what gives the big win.
    >> Well, it's not only aio. Multithreaded I/O also helps alot -- all this,
    >> say, to utilize a raid array with many spindles.
    >>
    >> But even single-threaded I/O but in large quantities benefits from O_DIRECT
    >> significantly, and I pointed this out before.
    >
    > Which shouldn't be true. There is no fundamental reason why
    > ordinary writes should be slower than O_DIRECT.
    >
    Other than the copy to buffer taking CPU and memory resources.

    --
    Bill Davidsen <davidsen@tmr.com>
    "We have more to fear from the bungling of the incompetent than from
    the machinations of the wicked." - from Slashdot

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