Re: [Qemu-devel] [Bug 899140] Re: Problem with Linux Kernel Traffic Control

[Stefan Hajnoczi]

On Wed, Dec 14, 2011 at 02:42:12PM -0000, Vincent Autefage wrote:
> Ok so the *Intel e1000* seems the only card which is impacted by the
> bug.

Let me recap with a summary of your debugging:

QEMU 0.14.0, 0.15.0, and 1.0 built from source all have poor network
performance below a 20 Mbit/s limit set with tc inside the guest.

Ubuntu's 0.14.0 QEMU package does not have poor network performance.

This problem only occurs with the emulated e1000 device.  All other
emulated NICs operate correctly.

Now you could diff the e1000 emulation code to get the code changes
between vanilla and Ubuntu:

 $ diff -u qemu-0.14.0-vanilla/hw/e1000.c qemu-0.14.0-ubuntu/hw/e1000.c

(It's possible that there are no significant changes and this bug is
caused by something outside e1000.c but this is place to check first.)

Or you could even try copying Ubuntu's e1000.c into the vanilla QEMU
source tree and retesting to see if the behavior changes.

Stefan