Re: Time sliced CFQ io scheduler

Nick Piggin
2004-12-08T07:20:00Z

On Wed, 2004-12-08 at 08:11 +0100, Jens Axboe wrote:
> On Wed, Dec 08 2004, Nick Piggin wrote:
> > On Wed, 2004-12-08 at 07:55 +0100, Jens Axboe wrote:

> > > Currently I think the time sliced cfq is the best all around. There's
> > > still a few kinks to be shaken out, but generally I think the concept is
> > > sounder than AS.
> > >
> >
> > But aren't you basically unconditionally allowing a 4ms idle time after
> > reads? The complexity of AS (other than all the work we had to do to get
> > the block layer to cope with it), is getting it to turn off at (mostly)
> > the right times. Other than that, it is basically the deadline
> > scheduler.
>
> Yes, the concept is similar and there will be time wasting currently.
> I've got some cases covered that AS doesn't, and there are definitely
> some the other way around as well.
>

Oh? What have you got covered that AS doesn't? (I'm only reading the
patch itself, which isn't trivial to follow).

> If you have any test cases/programs, I'd like to see them.
>

Hmm, damn. Lots of stuff. I guess some of the notable ones that I've
had trouble with are OraSim (Oracle might give you a copy), Andrew's
patch scripts when applying a stack of patches, pgbench... can't
really remember any others off the top of my head.

I've got a small set of basic test programs that are similar to the
sort of tests you've been running in this thread as well.