Re: CSCAN I/O scheduler for 2.6.10 kernel

["Vishal Patil" <vishpat@gmail.com>]

In that case it would be a normal elevator algorithm and that has a
possiblity of starving the requests at one end of the disk.

- Vishal

On 4/4/06, Bill Davidsen <davidsen@tmr.com> wrote:
> Vishal Patil wrote:
> > Maintain two queues which will be sorted in ascending order using Red
> > Black Trees. When a disk request arrives and if the block number it
> > refers to is greater than the block number of the current request
> > being served add (merge) it to the first sorted queue or else add
> > (merge) it to the second sorted queue. Keep on servicing the requests
> > from the first request queue until it is empty after which switch over
> > to the second queue and now reverse the roles of the two queues.
> > Simple and Sweet. Many thanks for the awesome block I/O layer in the
> > 2.6 kernel.
> >
> Why both queues sorting in ascending order? I would think that one
> should be in descending order, which would reduce the seek distance
> between the last i/o on one queue and the first on the next.
>
> --
>     -bill davidsen (davidsen@tmr.com)
> "The secret to procrastination is to put things off until the
>   last possible moment - but no longer"  -me
>


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