Messages in this thread | | | Date | Thu, 20 Oct 2005 19:07:06 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH linux-2.6-block:master 02/05] blk: update ioscheds to use generic dispatch queue |
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On Fri, Oct 21 2005, Tejun Heo wrote: > I think we're currently talking about two issues.
I think so too :)
> 1. Is @sort=0 case useful? > > Currently all ioscheds dispatch requests in sorted order. I was > afraid that sorting again might result in less efficient seek pattern > although I'm not quite sure whether or how that will happen. That's why > I added the @sort argument to elv_dispatch_insert(). If sorting cannot > hurt in any case, we might sort unconditionally and remove @sort > argument from elv_dispatch_insert().
That's what I ended up merging, elv_dispatch_sort() and it only takes q and rq as parameters.
> 2. Why @force is used to turn on @sort?
Yes, that was my question :-)
> The reasoning was that, when a iosched is forced dispatched, it > doesn't have control over many aspects of IO scheduling, so it cannot > produce good ordering of dumped requests, which actually is true for > cfq. That's why @sort is turned on while force-dispatching requests.
Well that's not quite my question, it is the opposite - why would you not want to sort?
> Maybe just removing @sort argument from elv_dispatch_insert() and > sorting always is the way to go?
See the merged stuff, I think so. I just don't see any reason at all to tie 'force' and 'sort' together.
-- Jens Axboe
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