Ben,
I am facing the performance issue when we try to bond the multiple
interfaces with virtual interface. It could be related to this thread. 
My questions are,
*) When we use mulitple NICs, will the performance of overall system  be
summation of all individual lines  XX bits/sec. ?
*) What are the factors improves the performance if we have multiple
interfaces?. [ kind of tuning the parameters in proc ]

Breno, 
I hope this thread will be helpful for performance issue which i have
with bonding driver.

Jeba
On Thu, 2008-01-10 at 16:36 +0000, Ben Hutchings wrote:

Breno Leitao wrote:

quoted

Hello, 

I've perceived that there is a performance issue when running netperf
against 4 e1000 links connected end-to-end to another machine with 4
e1000 interfaces. 

I have 2 4-port interfaces on my machine, but the test is just
considering 2 port for each interfaces card.

When I run netperf in just one interface, I get 940.95 * 10^6 bits/sec
of transfer rate. If I run 4 netperf against 4 different interfaces, I
get around 720 * 10^6 bits/sec.

<snip>

I take it that's the average for individual interfaces, not the
aggregate?  RX processing for multi-gigabits per second can be quite
expensive.  This can be mitigated by interrupt moderation and NAPI
polling, jumbo frames (MTU >1500) and/or Large Receive Offload (LRO).
I don't think e1000 hardware does LRO, but the driver could presumably
be changed use Linux's software LRO.

Even with these optimisations, if all RX processing is done on a
single CPU this can become a bottleneck.  Does the test system have
multiple CPUs?  Are IRQs for the multiple NICs balanced across
multiple CPUs?

Ben.