Re: [PATCH][CFT] new IO scheduler for 2.4.20

[Neil Schemenauer <nas@python.ca>]

Con Kolivas wrote:
> How does this compare to akpm's read-latency2 patch that he posed some
> time ago? That seems to make a massive difference but was knocked back
> for style or approach.

It looks like they do fairly similar things.  Andrew's patch puts
unmergable read requests at a fixed distance from the front of the
queue.  My patch lets unmerged reads skip max((reads - writes), 0)
requests.  That's probably more fair when lots of reads and writes are
in queue.

Andrew's idea of always allowing a merge is probably a good idea and
could be adopted.

My patch uses a fixed deadline for requests (similar to Jen's deadline
scheduler).  I'm not sure if that's an advantage or not.  Note that the
deadline of writes are ignored when inserting a read.

I didn't change the size of the request queue.  I can't find where that
gets set in 2.4.20. :-(

Sorry for the hand-waving.  I didn't know about Andrew's patch and I
obviously didn't do enough testing yet.

  Neil