Comment 39 for bug 709245

Hi warmcat,

On Sun, Aug 28, 2011 at 4:32 PM, warmcat <email address hidden> wrote:
> Ming-Lei it sounds like a really good explanation.  But when I test it,
> I don't see any real difference on USB memory stick before and after.
> Maybe my test is broken somehow?

Could you check if you have applied patch, built kernel and update correctly?
What is your board and version? and could you post out your kernel config?

>
> 8GB no-name USB stick
>
> Before the patch -->
>
> root@linaro:~# dd if=/dev/urandom of=/media/dump bs=40960 count=1000
> 1000+0 records in
> 1000+0 records out
> 40960000 bytes (41 MB) copied, 21.9735 s, 1.9 MB/s
>
> root@linaro:~# dd if=/dev/urandom of=/media/dump bs=40960 count=1000
> 1000+0 records in
> 1000+0 records out
> 40960000 bytes (41 MB) copied, 21.3798 s, 1.9 MB/s
>
> root@linaro:~# dd if=/dev/urandom of=/media/dump bs=40960 count=1000
> 1000+0 records in
> 1000+0 records out
> 40960000 bytes (41 MB) copied, 21.3694 s, 1.9 MB/s
>
>
> After the patch -->
>
> root@linaro:~# mount /dev/sda1 /media/
> root@linaro:~# dd if=/dev/urandom of=/media/dump bs=40960 count=1000
> 1000+0 records in
> 1000+0 records out
> 40960000 bytes (41 MB) copied, 21.6143 s, 1.9 MB/s
> root@linaro:~# dd if=/dev/urandom of=/media/dump bs=40960 count=1000
> 1000+0 records in
> 1000+0 records out
> 40960000 bytes (41 MB) copied, 21.6175 s, 1.9 MB/s
> root@linaro:~# dd if=/dev/urandom of=/media/dump bs=40960 count=1000
> 1000+0 records in
> 1000+0 records out
> 40960000 bytes (41 MB) copied, 21.5983 s, 1.9 MB/s

I think the patch should have some changes on the test result.

>
> I like the idea the delay is coming from L2 cache not being evicted
> until something else forces it a lot though.

The delay is coming from the delayed ehci irq or lost ehci irq, and which
is coming from the not up-to-date qtd descriptor.

thanks,
--
Ming Lei