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    SubjectRe: QUEUE_FLAG_NONROT and merges
    On Tue, 14 Oct 2008 09:54:08 +0200
    Jens Axboe <jens.axboe@oracle.com> wrote:

    > On Tue, Oct 14 2008, Pierre Ossman wrote:
    > > Hi Jeff,
    > >
    > > I noticed you've added a new flag to indicate that the drive has no
    > > seek costs and I figured it would be a good idea to use that on the
    > > MMC/SD cards.
    >
    > That was me, actually...
    >

    Sorry, this was meant for you of course. I don't know how I got things
    mixed up there. I guess I'll have to blame lack of coffee this
    morning. :)

    > > Since the name isn't entirely clear in what is implied, I just wanted
    > > to check that there are no plans to assume that there is negligable
    > > request overhead for queues with this flag. I.e. the flag should
    > > indicate that the elevator doesn't have to care about seeks, but it
    > > should still try to merge requests to reduce the transaction overhead.
    >
    > Sounds about right. The flag is just meant to indicate zero-seek cost,
    > as devices will still have per-command overheads, merging is still
    > applicable.
    >
    > So yes, you want to set that flag for mmc/sd cards, definitely.
    >

    Great. I'll get a patch out ASAP.

    Rgds
    --
    -- Pierre Ossman

    Linux kernel, MMC maintainer http://www.kernel.org
    rdesktop, core developer http://www.rdesktop.org

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