Re: Disk scheduling policy (Re: NEW_BUFQ_STRATEGY)

On Mon, Dec 01, 2003 at 03:47:44PM -0800, Matt Thomas wrote:
> At 03:16 PM 12/1/2003, Jason Thorpe wrote:
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> >On Dec 1, 2003, at 3:11 PM, Thor Lancelot Simon wrote:
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> My assumption was that you *always* drain the current queue before
> switching to other queue.  In that scenario, there is no starvation.

The way I read the SGI text, they do N requests from queue A, then
N requests from queue B, and so forth.  A simple implementation of
this seems like it might disrupt the elevator sort quite badly, so I
wonder if they actually did something more clever.

I can think of a reasonably simple way to tune "N" if we can 
characterize the seek time of the disk... but that seems dangerous.

-- 
 Thor Lancelot Simon	                                      [email protected]
   But as he knew no bad language, he had called him all the names of common
 objects that he could think of, and had screamed: "You lamp!  You towel!  You
 plate!" and so on.              --Sigmund Freud