Messages in this thread | | | Date | Wed, 31 May 2006 08:11:10 +0200 | From | Jens Axboe <> | Subject | Re: [rfc][patch] remove racy sync_page? |
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On Tue, May 30 2006, Mark Lord wrote: > Linus wrote: > >(Yes, tagged queueing makes it less of an issue, of course. I know, > > My observations with (S)ATA tagged/native queuing, is that it doesn't make > nearly the difference under Linux that it does under other OSs. > Probably because our block layer is so good at ordering requests, > either from plugging or simply from clever disk scheduling.
Hmm well, I have seen 30% performance increase for a random read work load with NCQ, I'd say that is pretty nice. And of course there's the whole write cache issue, with NCQ you _could_ get away with playing more safe and disabling write back caching.
NCQ helps us with something we can never fix in software - the rotational latency. Ordering is only a small part of the picture.
Plus I think that more recent drives have a better NCQ implementation, the first models I tried were pure and utter crap. Lets just say it didn't instill a lot of confidence in firmware engineers at various unnamed drive companies.
-- Jens Axboe
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