Messages in this thread | | | Date | Fri, 27 Nov 2009 09:23:16 +0100 | From | Jens Axboe <> | Subject | Re: [RFC,PATCH] cfq-iosched: improve async queue ramp up formula |
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On Thu, Nov 26 2009, Corrado Zoccolo wrote: > The introduction of ramp-up formula for async queue depths has > slowed down dirty page reclaim, by reducing async write performance. > This patch improves the formula by considering the remaining slice. > > The new formula will allow more dispatches at the beginning of the > slice, reducing them at the end. > This will ensure that we achieve good throughput, without the risk of > overrunning the allotted timeslice. > > The threshold is automatically increased when sync I/O is not > intermingled with async, in accordance with the previous incarnation of > the formula.
The slow ramp up is pretty much essential to being able to have low latency for the sync reads, so I'm afraid this will break that. I would prefer doing it through memory reclaim detection, like the other patch you and Motohiro suggested.
-- Jens Axboe
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