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SubjectRe: [PATCH 1/8] block: limit default readahead size for small devices
On Mon, Nov 21, 2011 at 06:00:04PM +0800, Christoph Hellwig wrote:
> On Mon, Nov 21, 2011 at 05:18:20PM +0800, Wu Fengguang wrote:
> > This looks reasonable: smaller device tend to be slower (USB sticks as
> > well as micro/mobile/old hard disks).
> >
> > Given that the non-rotational attribute is not always reported, we can
> > take disk size as a max readahead size hint. This patch uses a formula
> > that generates the following concrete limits:
>
> Given that you mentioned the rotational flag and device size in this
> mail, as well as benchmarking with an intel SSD - did you measure
> how useful large read ahead sizes still are with highend Flash device
> that have extremly high read IOP rates?

I don't know -- I don't have access to such highend devices.

However the patch changelog has the simple test script. It would be
high appreciated if someone can help collect the data :)

Thanks,
Fengguang


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