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

Oliver Neukum oneukum at suse.de
Mon Nov 26 10:10:43 EST 2012

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?

> 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.


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