[netperf-talk] global question concerning Netperf test and SMP support

[Hangbin Liu]

On Thu, 2012-03-29 at 10:01 +0200, Simon Duboue wrote:
> Hello everyone, 
> 
> I am quite new in the Netperf community but I follow actively this
> talk. 
> 
> I'm using netperf 2.4 to test a multi core platform with a 10G NIC. 
> I have a host which is based on a 8 cores SoC and with a Linux SMP 3.0
> and a client based on a dual core motherboard with a Suse 11. 
> 
> First, I have a question concerning the test of the loopback local
> interface (lo): 
> -how could we interpret the results provided by Netperf in term of
> throughput? is it limiting for the rest of the test concerning the
> network? 

I think lo test only affects the TCP/IP stack, no relation with NIC
drivers.
> 
> Then concerning the network test itself, I get a maximal throughput of
> 4 Gbits/s with a unidirectional UDP STREAM test from client to host. 
> I am waiting more than that (8-9 GBit/s) and I am asking what could be
> limiting. I am already performing Jumbo frames and I suppose that
> Linux kernel are auto tuned concerning buffer and socket. I try to
> tune Linux by increasing the max buffer size but the effects are quite
> limited. I also modify timestamps, arp filtering and once again the
> effects are limited. 
> 

Our TCP_STREAM and UDP_STREAM test could reach > 9.5G/s on local lab
with 10G switch and NICs. you can try to enable gro or something else.

And please paste your command lines and NIC drivers.

> In TCP STREAM test, I also run two tests: a standard TCP STREAM and a
> standard TCP MAERTS and the results are very different with a 10x
> ratio for the TCP MAERTS. How is it possible? 
> 
> The last question concerns the implementation of TCPIP stack in Linux
> kernel. Does it fully perform SMP or does TCPIP stack is reserved to a
> defined core. 
> 
> I hope being clear. If not, please consider these mistakes as beginner
> ones. 
> 
> Thank you in advance. 
> 
> Simon Duboué
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