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    SubjectRe: disk head scheduling
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    Linus Torvalds wrote:
    > Note that it really shouldn't be all that much work to change the actual
    > ll_rw_block.c layer - all the work is really in the devices themselves
    > (adding the mapping function, and making sure the SCSI layer in particular
    > can live with multiple queues).

    To save on the (indirect) function call, I would like to suggest:

    unsigned char **queue_numbers;

    queue_number = queue_numbers[major][minor];

    That would require 256 bytes of storage for every major that is in use
    in the system. That's two kilobytes for 8 majors in use. Acceptable
    I'd say.

    Adding just a teeny bit of "policy" in a central place:

    queue_number = queue_numbers[major][minor>>3];

    reduces the amount of memory used by a factor of 8, but forces devices
    to have the same queue for every 8 minor numbers (e.g. partitions on a
    disk).

    Roger.

    --
    ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 **
    *-- BitWizard writes Linux device drivers for any device you may have! --*
    * Never blow in a cat's ear because if you do, usually after three or *
    * four times, they will bite your lips! And they don't let go for at *
    * least a minute. -- Lisa Coburn, age 9

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