Re: [rfc][patch] remove racy sync_page?

Jens Axboe
2006-05-31T06:11:10Z

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