Hello, all.

I play the dpdk-1.2.3r1 with examples.

But I can not achieve the line-rate packet receive performance,
and the performance is not scale with multiple ports.

For example, in example l2fwd, I have tested two cases with 2 ports, and 4
ports,
using belowed command line each

./build/l2fwd -cf -n3 -- -p3
./build/l2fwd -cf -n3 -- -pf

But both cases, the aggregated performance are not scale.

== experiments environments ==
- Two Intel 82599 NICs (total 4 ports)
- Intel Xeon X5690  @ 3.47GHz * 2 (total 12 cores)
- 1024 * 2MB hugepages
- Linux 2.6.38-15-server
- Each ports receiving 10Gbps of traffic of 64 bytes packets, 14.88Mpps.

*1. Packet forwarding performance*

In 2 ports case,  receive performance is 13Mpps,
In 4 ports case,  not 26Mbps, only 16.8Mpps.

Port statistics ====================================
Statistics for port 0 ------------------------------
Packets sent:                  4292256
Packets received:              6517396
Packets dropped:               2224776
Statistics for port 1 ------------------------------
Packets sent:                  4291840
Packets received:              6517044
Packets dropped:               2225556
Aggregate statistics ===============================
Total packets sent:            8584128
Total packets received:       13034472
Total packets dropped:         4450332
====================================================

Port statistics ====================================
Statistics for port 0 ------------------------------
Packets sent:                  1784064
Packets received:              2632700
Packets dropped:                848128
Statistics for port 1 ------------------------------
Packets sent:                  1784104
Packets received:              2632196
Packets dropped:                848596
Statistics for port 2 ------------------------------
Packets sent:                  3587616
Packets received:              5816344
Packets dropped:               2200176
Statistics for port 3 ------------------------------
Packets sent:                  3587712
Packets received:              5787848
Packets dropped:               2228684
Aggregate statistics ===============================
Total packets sent:           10743560
Total packets received:       16869152
Total packets dropped:         6125608
====================================================

*2. Packet receiving performance*
I fix the codes for only receiving packets (not forwarding),
the performance is still not scalable as each 13.3Mpps, 18Mpps.

Port statistics ====================================
Statistics for port 0 ------------------------------
Packets sent:                        0
Packets received:              6678860
Packets dropped:                     0
Statistics for port 1 ------------------------------
Packets sent:                        0
Packets received:              6646120
Packets dropped:                     0
Aggregate statistics ===============================
Total packets sent:                  0
Total packets received:       13325012
Total packets dropped:               0
====================================================

Port statistics ====================================
Statistics for port 0 ------------------------------
Packets sent:                        0
Packets received:              3129624
Packets dropped:                     0
Statistics for port 1 ------------------------------
Packets sent:                        0
Packets received:              3131292
Packets dropped:                     0
Statistics for port 2 ------------------------------
Packets sent:                        0
Packets received:              6260908
Packets dropped:                     0
Statistics for port 3 ------------------------------
Packets sent:                        0
Packets received:              6238764
Packets dropped:                     0
Aggregate statistics ===============================
Total packets sent:                  0
Total packets received:       18760640
Total packets dropped:               0
====================================================

The question is that
1. How I can achieve each port receiving full 14.88Mpps ?
    What might be the bottleneck in current environment?
2. Why the performance using multiple ports is not scale?
    I guess doubling ports shows the doubling the receiving performance,
    but it shows not. I am curious about what is limiting the packet
receivng performance.

Thanks,
Shinae