RSS mode performance in ixgbe (82599) driver

RSS mode performance in ixgbe (82599) driver

[J.Hwan Kim]

Hi, everyone

I'm testing the RSS mode throughput of Intel ixgbe 82599 driver.
My server's specification is Xeon 3GHz (4cores) and PCIe speed is 
2.5Gx8lanes,
and DD2 memory is about 600~700MHz.

When I enable the RSS(receive side scaling) mode with 4 Rx queues,
the Rx performance is below than when I use a single queue.

I don't know how the cores operate, whether the cores run in sequence
or simultaneously at the same time.

I want to know the mechanism in general how the multi-cores run
and the reason why the performance of ixgbe driver in rss mode is below
non-rss mode.

Thanks in advance.

Best Regards,
J.Hwan Kim

Re: RSS mode performance in ixgbe (82599) driver

[Eric Dumazet]

Le mardi 09 août 2011 à 21:03 +0900, J.Hwan Kim a écrit :
> Hi, everyone
> 
> I'm testing the RSS mode throughput of Intel ixgbe 82599 driver.
> My server's specification is Xeon 3GHz (4cores) and PCIe speed is 
> 2.5Gx8lanes,
> and DD2 memory is about 600~700MHz.
> 
> When I enable the RSS(receive side scaling) mode with 4 Rx queues,
> the Rx performance is below than when I use a single queue.
> 
> I don't know how the cores operate, whether the cores run in sequence
> or simultaneously at the same time.
> 
> I want to know the mechanism in general how the multi-cores run
> and the reason why the performance of ixgbe driver in rss mode is below
> non-rss mode.

CC netdev, as these kind of stuff is better hosted on netdev

You should make sure your 4 rx queues are serviced by different cpus, or
else, one cpu could be the bottleneck.

cat /proc/interrupts