[Cerowrt-devel] debloating the Pi, maybe not.

Dave Taht dave.taht at gmail.com
Mon Nov 26 10:29:36 EST 2012

On Mon, Nov 26, 2012 at 4:10 PM, Oliver Neukum <oneukum at suse.de> wrote:
> On Friday 23 November 2012 17:43:24 Dave Taht wrote:
>> I was donated a raspberry pi in cambridge and got it booted today.
>> It's a very cool
>> box, an arm6, running debian, with hard floating point, and getting a complete
>> development environment running, getting it to do mesh networking,
>> graphics, apache, etc, on a 16GB SD card, was a breeze.
>> But as for network performance:
>> It only comes up at 100Mbit, and as noted elsewhere the ethernet chip
>> is hooked up over USB.
>> dmesg
>> [3.078644] smsc95xx 1-1.1:1.0: eth0: register 'smsc95xx' at
>> usb-bcm2708_usb-1.1, smsc95xx USB 2.0 Ethernet, b8:27:eb:18:fc:ac
>> The best the 3.2 kernel based networking can do is about 75Mbit/sec.
>> This eats 68% of cpu in the "system" (sy in top) and 30% in si (system
>> interrupt)
> Wow. What did you do to saturate the system like this? Blow empty
> UDP packages into the net?

A single TCP stream.

I built netperf 2.6 with --enable-demo, ran netserver on it, and hit it
with single

netperf -l60 -H pi

I don't remember if the performance I got from it was with -t
TCP_STREAM or -t TCP_MAERTS (probably the latter).

I will re-run the test with iperf, also, the next time I boot it.

Other than this it's a pretty darn cool board, and if I had time I'd
dream up a zillion projects for it... It does look rather easy to
compile or cross compile kernels for it, too...

>> I had had some hope of this being a good box to put some test tools on,
>> but with performance like this, I am back to leveraging the mips stuff.
>> That said, I do intend to poke at the driver and update to 3.6 when
>> I get a chance, since we have patches lying around for both this
>> chip and the usbnet code.
> Nothing for performance in the mean time. Note that we don't try to
> do interrupt mitigation in usbnet.


>         Regards
>                 Oliver

Dave Täht

Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html

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