Re: [PATCH] speed up SATA

[Jeff Garzik]

Jens Axboe wrote:
> Here's a quickly done patch that attempts to adjust the value based on a
> previous range of completed requests. It changes ->max_sectors to be a
> hardware limit, adding ->optimal_sectors to be our max issued io target.
> It is split on READ and WRITE. The target is to keep request execution
> time under BLK_IORATE_TARGET, which is 50ms in this patch. read-ahead
> max window is kept within a single request in size.
>
> So this is pretty half-assed, but it gets the point across. Things that
> should be looked at (meaning - should be done, but I didn't want to
> waste time on them now):
>
> - I added the hook to see how many in-drive queued requests you have, so
>   there's the possibility to add tcq knowledge as well.
>
> - The optimal_sectors calculation is just an average of previous maximum
>   with current maximum. The scheme has a number of break down points,
>   for instance writes starving reads will give you a bad read execution
>   time, further limiting ->optimal_sectors[READ]


Makes me pretty happy... :)

	Jeff



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