Messages in this thread |  | | | Date | Wed, 8 Dec 2004 08:26:16 +0100 | | From | Jens Axboe <> | | Subject | Re: Time sliced CFQ io scheduler |
On Wed, Dec 08 2004, Nick Piggin wrote: > 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).
You are only thinking in terms of single process characteristics like will it exit and think times, the inter-process characteristics are very hap hazard. You might find the applied code easier to read, I think.
> > 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.
The patch scripts case is interesting, last night (when committing other patches) I was thinking I should try and bench that today. It has a good mix of reads and writes.
There's still lots of tuning in the pipe line. As I wrote originally, this was basically just a quick hack that I was surprised did so well :-) It has grown a little since then and I think the concept is really sound, so I'll continue to work on it.
> 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.
Ok
-- Jens Axboe
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