Messages in this thread | | | Date | Fri, 11 Nov 2005 14:21:34 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH] as-iosched: update alias handling |
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On Fri, Nov 11 2005, Nick Piggin wrote: > Jens Axboe wrote: > >On Thu, Nov 10 2005, Tejun Heo wrote: > > > >>Unlike other ioscheds, as-iosched handles alias by chaing them using > >>rq->queuelist. As aliased requests are very rare in the first place, > >>this complicates merge/dispatch handling without meaningful > >>performance improvement. This patch updates as-iosched to dump > >>aliased requests into dispatch queue as other ioscheds do. > >> > >>Signed-off-by: Tejun Heo <htejun@gmail.com> > > > > > >In theory the way 'as' handles the aliases is faster since we postpone > >pushing them to the dispatch list at the same point (and they have > >strong (if not identical) locality). But it is much simpler to just > >shove the offending requests onto the dispatch list. > > > >It's really up to Nick - what do you think? Leaving patch below. > > > > I thought this was pretty cool, but in reality it could be that the > cost / benefit actually goes the wrong way due to added complexity > and rarity of alised requests. > > Hmm... I can't bear to ack it ;) I'll close my eyes and let Jens > make the call!
Heh well, I am a sucker for simplicity especially when it's for corner cases where the more advanced solution will at most save you a full seek.
> >>Jens, I've tested this change for several hours, but it might be > >>better to postpone this change to next release. It's your call. > >> > > It could go into mm now, but probably leave it for 2.6.16 unless > you have some other reason to really need it.
Agree, I've shoved it into the 'post-2.6.15' branch.
-- Jens Axboe
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