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    SubjectRe: dd PATCH: add conv=direct
    philip copeland did a whole set of patches for coreutils to allow
    directio for both read write and mixed sizes even
    the rpm is at
    http://oss.oracle.com/projects/ocfs/files/source/RHAT/RHAS3/coreutils-4.5.3-33.src.rpm,
    I think he took it up with the maintainers but so far had no luck

    it makes sense to have this stuff, we use it a lot.

    Wim

    On Fri, Apr 09, 2004 at 10:37:37AM +1000, Anton Blanchard wrote:
    >
    > Hi,
    >
    > > OK, I can see that one. But it seems like a pretty small benefit to me
    > > -- CPU utilization is already really low.
    >
    > Maybe not to you but it does make a big difference on our 500 disk setup.
    > At the moment we use dd to do an initial sniff, then ext3 utils to do
    > O_DIRECT reads/writes. With O_DIRECT read/write in dd we could use it
    > instead. (We are basically interested in IO performance that a database
    > would see).
    >
    > > Um, that sounds like a bad idea to me. It seems to me it's the kernel's
    > > responsibility to figure out "hey, looks like a streaming read - let's
    > > not blow out the buffer cache trying to hold 20GB on a 512M system." If
    > > you're saying that the kernel guys have given up and the established
    > > wisdom is now "you gotta use O_DIRECT if you don't want to throw
    > > everything else out due to streaming data", well... I'm disappointed.
    >
    > When you start hitting memory bandwidth limits, O_DIRECT will help you.
    > Sure it wont be an issue for your dd copy scenario, but I wanted to point
    > out there are other valid uses for it.
    >
    > Anton
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