[meta-freescale] P4080 IP routing performance regression

[Björn Stenberg]

Hi all.

We have found a performance regression in the linux-qoriq kernel released for dora. IP routing performance for small packets has decreased by over 20% between kernels 3.0.51 (dylan) and 3.8.13 (dora).

The test uses two 10 Gbit interfaces on a p4080ds board. We feed UDP packets at full speed into the first interface and measure how many packets make it out of the second interface. Here are the results:

Frame  Kernel  Kernel  
Size   3.0.51  3.8.13  Change
----   ------  ------  ------
64     28.8    21.9    -24%
128    50.9    38.8    -24%
256    90.8    71.1    -22%
512    99.1    99.1   
1024   100     100     
1280   100     100     
1518   99.9    99.9    
2048   100     100     
4096   100     100     
8192   100     100     
8980   100     100     

The values are in percent, out of the theoretical maximum. These numbers are for IPv6, but IPv4 looks roughly the same.

These are the kernel configurations used:

3.0.51 kernel config: http://pastebin.com/L0c0fTuU
3.8.13 kernel config: http://pastebin.com/wbZcVGQM

-- 
Björn