Hi~

I have a question about DPDK & QPI performance issue in Romley platform.
Recently, I use DPDK example, l2fwd, to test DPDK's performance in my Romley platform.
When I try to do the test, crossing used CPU, I find the performance dramatically decrease.
Is it true? Or any method can prove the phenomenon?

In my opinion, there should be no this kind of issue here due to QPI have enough bandwidth to deal the kinds of case.
Thus, I am so amaze in our results and can not explain it.
Could someone can help me to solve this problem.

Thank a lot!

My testing environment describe as below:

Platform:         Romley
CPU:                E5-2643 * 2
RAM:               Transcend 8GB PC3-1600 DDR3 * 8
OS:                 Fedora core 14
DPDK:            v1.3.1r2, example/l2fwd
Slot setting:
                      SlotA is controled by CPU1 directly.
                      SlotB is controled by CPU0 directly.

DPDK pre-setting:
a. BIOS setting:
    HT=disable
b. Kernel paramaters
    isolcpus=2,3,6,7
    default_hugepagesz=1024M
    hugepagesz=1024M
    hugepages=16
c. OS setting:
    service avahi-daemon stop
    service NetworkManager stop
    service iptables stop
    service acpid stop
    selinux disable

Example program Command:
a. SlotB(CPU0) -> CPU1
    #>./l2fwd -c 0xc -n 4 -- -q 1 -p 0xc

b. SlotA(CPU1) -> CPU0
    #>./l2fwd -c 0xc0 -n 4 -- -q 1 -p 0xc0

Results:
     use frame size 128 bytes

CPU Affinity	Slot A (CPU1)	Slot B (CPU0)
CPU0	15.9%	96.49%
CPU1	90.88%	24.78%

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