Re: [PATCH] AHCI prefetch

[Jeff Garzik <jeff@garzik.org>]

Tejun Heo wrote:
> On Sat, Mar 04, 2006 at 12:35:05PM -0500, Jeff Garzik wrote:
>
> > This patch has been sitting in my tmp directory for ages.
> >
> > We should probably turn this on, though the practical difference is
> > probably minimal.
>
>
> The patch works okay on my machine (ICH7R) although the patch didn't
> apply to #upstream.  I'm not very sure about this change though.
>
> 1. Why apply it only to ATAPI devices?  ATA devices can benefit to.
>    If it's because this bit shouldn't be turned on for NCQ, we can
>    turn it on conditionally.  We'll probably need similar condition
>    for ATAPI devices too if we support FIS-based PM switching.

Main reason is that it will largely only have benefits on ATAPI devices, 
and I've only tested it on ATAPI devices.


> 2. I'm a bit skeptical whether this change will bring any noticeable
>    performance improvement.  OTOH, this seems to be a good source for

Agreed.


>    obscure problems on some controllers which might not implement/test
>    this feature properly.  As more controllers implement AHCI spec,
>    the possibility grows.

Agreed.


> Anyways, here's the patch regenerated against #upstream.

Could I trouble you for a resend, with a proper signed-off-by and patch 
description?

	Jeff



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