Re: Disk scheduling policy (Re: NEW_BUFQ_STRATEGY)

On Dec 1, 2003, at 12:07 PM, Thor Lancelot Simon wrote:

> | In 6.5.8, the queues are split. Doing this permits queuing delayed 
> writes
> | into one queue, while synchronous writes and reads are entered into 
> another
> | queue. In 6.5.8 the disk driver will alternate between queues. This 
> ensures
> | that a large queue of delayed write requests will not adversely 
> impact
> | interactive response. If both delayed writes and other requests are 
> pending,
> | the driver will alternate between them, issuing several delayed 
> writes,
> | then several of the other requests. Selecting several from each 
> queue each
> | time, rather than just one from each queue each time, makes 
> sequential
> | I/O faster and disk performance is maximized.

This is a pretty cool, and fairly simple, algorithm.  I bet it could be 
implemented as a back-end to the new bufq code pretty easily.

         -- Jason R. Thorpe <[email protected]>