[fedora-arm] Slow USB storage on A9 processors

[Jeffrey Bastian]

On 2011-09-13 11:18, Mark Salter wrote:
>> On 2011-09-13 10:18, Mark Salter wrote:
>>> The big write performance hits are worrisome, though. I'd be good to
>>> test on one kernel version with and without the patch just to make sure.
>>> Also comparing SD performance with and without nosmp passed on cmdline
>>> would be interesting.
>
> I already have a good idea what the results will look like for usb, so
> just the other four with sd-card.


I tested 2.6.40.3 with and without the DMA API patch set, and with and 
without the nosmp cmdline option.

The good news: the DMA API patch set does not seem to be responsible for 
the slow-down in SD card performance, it was equally slow with all 
2.6.40.3 variants.  The bad news: some other change between 2.6.35 and 
2.6.40 must be responsible, so there's a lot of bisecting to do.

See the bonnie++ results at:
http://jeffbastian.blogspot.com/2011/09/sd-card-speeds.html

Jeff