Hi,

I don't know if this topic is appropriate here, please direct me to a
better place if not.

I've been spending considerable time trying to measure the performance
of our 10G fabric that uses Intel X520 cards.  The primary test machine
has dual Intel(R) Xeon(R) CPU E5-2650 0 @ 2.00GHz chip 8-core chips and
96GB RAM.

The test machine is now running Ubuntu 12.04.4 server with kernel 3.11.0
with latest ixgbe driver 3.19.1.

Using iperf (2.0.5) I see about 9.39Gbs steady inbound transfers (there
are a few glitches where I've seen drop to 7Gbs but it recovers).  My
outbound transfers, however, are about 8.83Gbs steady and tend to be
more variable.

This is the best performance I can get on the server.

Interestingly when I boot the machine off the live CDROM image for
Ubuntu 12.04.4 desktop, I see nice steady 9.39Gbs in both directions.
This is the best performance i have seen with this card to-date.

I've spent a lot of time with these cards and in general they have be
very finicky, delivering inconsistent results from test to test, being
very sensitive to driver and kernel versions.

I've taken them from extremely erratic performance on Ubuntu 12.04.1
with the stock ixgbe 3.6.7 driver to much higher, more stable
performance simply by updating to ixgbe 3.11.33.  It would be nice to
see a stable flatline performance at line speeds on kernel 3.11 with the
3.19.1 driver.

I'm wondering if there is a known configuration profile that allows
these cards to perform at line speeds or if there are known issues or
hardware incompatibilities.

I know there are a lot of subtleties to performance tuning but
performance on other cards in our fabric (btw from Brocade) deliver very
consistent, stable, high performance line speed results over many tests.

I've been scratching my head for a while and am looking for a fresh
perspective or deeper understanding.

Thanks for any insight or pointers you can provide,

~jpr



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