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    SubjectRe: disk head scheduling
    On Wed, 24 Mar 1999, Gerard Roudier wrote:

    > You only thought IDE and it what I pointed out, btw.
    > For SCSI with 1 queue per device, if we are globally plugged we lose
    > time (think of SMP, and interruptions), and if we discard the plug, we
    > may break the coalescencing and sorting, and then just provide devices
    > with bunches small IOs.

    I admit that not implementing per-queue plugs at that time was a mistake.
    The time in which the plug is being held should be very short relative to
    actual I/O times, though, just enough to let the higher layers complete
    putting all those small requests and colaescencing them, which is a
    CPU <--> memory operation.

    Cheers,

    Gadi


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