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    SubjectRe: [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter
    On 03/17/2010 10:49 AM, Christoph Hellwig wrote:
    > On Tue, Mar 16, 2010 at 01:08:28PM +0200, Avi Kivity wrote:
    >
    >> If the batch size is larger than the virtio queue size, or if there are
    >> no flushes at all, then yes the huge write cache gives more opportunity
    >> for reordering. But we're already talking hundreds of requests here.
    >>
    > Yes. And rememember those don't have to come from the same host. Also
    > remember that we rather limit execssive reodering of O_DIRECT requests
    > in the I/O scheduler because they are "synchronous" type I/O while
    > we don't do that for pagecache writeback.
    >

    Maybe we should relax that for kvm. Perhaps some of the problem comes
    from the fact that we call io_submit() once per request.

    > And we don't have unlimited virtio queue size, in fact it's quite
    > limited.
    >

    That can be extended easily if it fixes the problem.

    --
    error compiling committee.c: too many arguments to function



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