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SubjectRe: disk head scheduling
Date
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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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