Re: Odd IDE performance drop 2.4 vs 2.6?

[Ondrej Zary]

Alan Cox wrote:
> On Llu, 2005-06-13 at 15:06, Nick Piggin wrote:
>
> > > Make sure you have pre-empt disabled and the antcipatory I/O scheduler
> > > disabled. 
> >
> > I don't think that those could explain it.
>
>
> Try it and see. The anticipatory I/O scheduler does horrible things to
> my IDE streaming performance numbers and to swap performance. It tries
> to merge I/O by delaying it which is deeply ungood when it comes to IDE
> streaming even if its good for general I/O.

Now I've tested it with preempt disabled and nothing has changed. When 
fiddling around with hdparm, I got about 16MB/s max. with 2.6.12-rc5. 
With 2.4.31, I got about 21MB/s when just the DMA was enabled 
(read-ahead and multcount set to 0 - changing them does not make almost 
any difference).

--
Ondrej Zary
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