Subject: Re: Disk scheduling policy (Re: NEW_BUFQ_STRATEGY)
To: Matt Thomas <>
From: Thor Lancelot Simon <>
List: tech-kern
Date: 12/01/2003 18:57:18
On Mon, Dec 01, 2003 at 03:47:44PM -0800, Matt Thomas wrote:
> At 03:16 PM 12/1/2003, Jason Thorpe wrote:
> >Hash: SHA1
> >
> >
> >On Dec 1, 2003, at 3:11 PM, Thor Lancelot Simon wrote:
> >
> 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	                            
   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