Re: [PATCH] speed up SATA

From: Jens Axboe
Date: Sun Mar 28 2004 - 12:41:28 EST

On Sun, Mar 28 2004, Jeff Garzik wrote:
> Jens Axboe wrote:
> >On Sat, Mar 27 2004, Jeff Garzik wrote:
> >
> >>I also wouldn't want to lock out any users who wanted to use SATA at
> >>full speed ;-)
> >
> >
> >And full speed requires 32MB requests?
> Full speed is the SATA driver supporting the hardware maximum. The

Come on Jeff, don't be such a slave to the hardware specifications. Just
because it's possible to send down 32MB requests doesn't necessarily
mean it's a super thing to do, nor that it automagically makes 'things
go faster'. The claim is that back-to-back 1MB requests are every bit as
fast as a 32MB request (especially if you have a small queue depth, in
that case there truly should be zero benefit to doing the bigger ones).
The cut-off point is likely even lower than 1MB, I'm just using that
figure as a value that is 'pretty big' yet doesn't incur too large
latencies just because of its size.

Jens Axboe

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