RE: [lwip-users] Optimizations forapplications requiring limited functionality.

[Roger Cover]

Greetings All,

I have made a discovery about my problem. I upgraded to version 9.1 of the 
Xilinx EDK at the same time I upgraded to lwIP 1.2.0. This EDK upgrade changed 
the GNU compiler suite that I am using. The new version of the compiler is the 
source of my problem. It generates much less efficient code, even with 
optimizations turned up.

The time spent in the lwIP library (for my UDP transfer) is now only 4.2% of 
the total transfer time. The bulk of the transfer time is in the Xilinx driver 
code (82%). The suggestions I received (thanks to Frédéric Bernon) to remove 
unused options from lwIP did reduce the time used by the lwIP library. 
Unfortunately, that was not my problem.

I am not sure why the new version of the compiler is so much less efficient. 
The old compiler produced code that transferred my 33554432-byte dataset in 5.8 
seconds. The code produced with new compiler takes 8.8 seconds (62.5% of the 
throughput performance). I will be looking into that.

My mistake was in presuming that the same driver source code would produce the 
same executable code under EDK 8.1 and EDK 9.1. That led me to the incorrect 
conclusion that the difference in performance was in the new lwIP library. 
Thank you all for your help.

Regards,
Roger W. Cover