Slow/broken USB and Ethernet on Snowballs/Origen boards?
jannis.pohlmann at codethink.co.uk
Wed Mar 14 20:04:17 UTC 2012
I am currently playing with a couple of the development boards for which
there are Linaro hwpacks and LEBs. Since what I am trying to do requires
a lot of disk and network I/O, I've been paying special attention to the
data transfer rates I can get out of these boards.
Below is a brief summary of my findings.
1) i.MX 53
* disk I/O using an external SSD drive is very good; good enough to
not require further measurements
* network I/O is approximately 9-10 MByte/s (perhaps more) which
seems ok given the 100 MBit/s Ethernet interface
2) Snowball (PDK, version 8)
* it seems to be impossible to get the USB OTG host mode to work,
therefore I could not test disk I/O with a USB drive; it appears
the OTG port on the version 8 board does not even have enough power
for a powered USB to actually go online (I am unaware of the
details of how this works unfortunately)
* performing network I/O with netcat casues netcat, ksoftirqd and
kworker to use ~33% of the CPU each, resulting in 100% CPU usage
only to handle the network data transfer
* the resulting network transfer rate is about 5.5 MByte/s, which
is significantly less than what the 100 MBit/s Ethernet interface
should be able to produce
* the internal USB hub runs at Full Speed (12 MBit/s), resulting in a
maximum USB disk I/O of 1.5 MByte/s
* since the board does not feature Ethernet itself, I tried to attach
a USB Ethernet controller to it, but of course the transfer rate
through that is by the I/O upper limit of the USB hub
* I did not test wireless but it is not feasible for what I am trying
to do anyway
I guess not all of this is surprising. The i.MX performs quite well but
unfortunately the CPU is quite slow compared to the others. However, I
wonder whether the USB OTG host mode issue on the Snowball is a known
problem? Also, network I/O occupying all of the CPU seems to be a bug or
at least a dodgy driver. About the Origen: I assume there is nothing
that can be done to have High Speed USB on it?
Thanks in advance! If anyone needs me to provide more information, I'll
gladly try to do that.
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