Re: [patch for 2.6.33? 1/1] ata: call flush_dcache_page() around PIO data transfers in libata-aff.c

[Jeff Garzik <jgarzik@pobox.com>]

On 02/03/2010 01:00 PM, Alan Cox wrote:
> On Wed, 03 Feb 2010 12:52:34 -0500
> Jeff Garzik<jgarzik@pobox.com>  wrote:
>
>> On 02/03/2010 12:46 PM, Alan Cox wrote:
>>> And indeed there was a patch I proposed in 2008 for this bounce
>>> buffer latency: See the archive
>>>
>>> Date: Fri, 29 Feb 2008 13:51:06 +0000
>>> From: Alan Cox<alan@lxorguk.ukuu.org.uk>
>>> To: linux-ide@vger.kernel.org, jeff@garzik.org
>>> Subject: [RFC PATCH] libata: PIO via bounce buffer
>>>
>>> although it doesn't deal with the dcache coherency issue and seems to
>>> need a little tweaking to apply due to other changes
>>
>> Yeah, I definitely liked the idea.  I wonder if we could do the
>> allocation during port_start rather than at the time of bounce?
>
> I actually got better numbers using kmalloc - no idea why - perhaps we
> get a hot page ?

Seems logical.  It surprises me, though, that being lockless and 
completely avoiding the kmalloc infrastructure wasn't a bigger win.  Was 
this measured on UP?

If your approach has the lowest cost, let's get it in...  I like 
decisions informed by hard data.  :)

	Jeff