Regression in Ubuntu 3.2.0.61 w/ Intel 3.8 driver

[George]

We saw a regression of flow setup rate with Open vSwitch. For a single VM and one netperf session, previously we got ~4000 connection per second. Now we can only get ~2500. We saw this is only for Intel NICs. Broadcom NIC shows the same performance as before.

The regression seems associated with the kernel. We are using Linux 3.2.0-61-generic. For default Intel NIC driver is 3.6.7-k, if we want to upgrade the intel driver to support UDP rx-flow-hash, we need to install: linux-backports-modules-net-3.2.0-61-generic
After updating the Intel driver to 3.8.21-NAPI, we got ~2500 cps for flow setup rate with one session in one vm. So I purged "linux-backports-modules-net-3.2.0-61-generic" and used the default Intel driver. Then the flow setup rate gets back to ~4000 tps.

With the linux-backports-module-net-3.2.0-58-generic, we saw no such regression with either Intel driver.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

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[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the Trusty HWE stack[0] in Precise and see if it also exhibits this bug? The Trusty HWE stack can be install with:

sudo apt-get install --install-recommends linux-generic-lts-trusty

If the bug does not exist in the Trusty HWE stack, one option would be to potentially just ride that Trusty stack in Precise. The other option would be for us to perform a reverse bisect to identify the fix and then backport it.

Thanks in advance

[0] https://wiki.ubuntu.com/Kernel/LTSEnablementStack#A12.04.4_.2B_13.10_Hardware_Enablement_Stack_Policies_and_Procedures

[Joseph Salisbury (jsalisbury)]

Also, we would like to collect some additional information about your system. From a terminal, please run the following:

apport-collect 1321035

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1321035

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Launchpad Janitor (janitor)]

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