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Microblaze + Lwip: compile with -O2 problem ...

Posted by debugasm on November 25, 2013


I have one system with Xilinx Spartan-6 that use Microblaze processor (8.50.c). In this system I have used Ethernet Lite. As a starting point I used the demo that I found in FreeRTOs.

Everything works fine if I use the system in "Debug" mode (compiling with -O0 optimization), but if I switch to "Release" mode (compiling with -O2 optimization) the transfer performance is much degraded.

Some advice on what I can check ?

Thanks very much.


Microblaze + Lwip: compile with -O2 problem ...

Posted by rtel on November 25, 2013

Is it just the Ethernet throughput that is degraded? Does everything else run at the specified rate (RTOS tick, etc.)?

I regularly test FreeRTOS at all optimisation levels so the problem is probably not in FreeRTOS - although I can't say for certain if I have run at high optimisation on a Microblaze. I would however think the driver code is the most likely source of potential issues. Is there anything in the driver code that is creating delays out of null loops by just incrementing up a variable? If so, is the variable declared volatile? Can you replace any such loops with a vTaskDelay() [as long as it is called from a task, not an interrupt, and the scheduler is running].


Microblaze + Lwip: compile with -O2 problem ...

Posted by debugasm on November 26, 2013


the problem is not FreeRTOs the problem is on Lwip TCP section. I have decrease the buffer (send and receive) on option of Lwip and the problem is resolved.

Now all working with -O2 optimization.

Thanks very much.


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