Is 0.4.3 NNOM c backend slower than CMSIS-5.9.0?

[bfs18]

I test the mnist-simple model in rt-thread environment and run model predict for 1000 times.
using CMSIS 5.9.0 backend, it consumes 1423 ms
using NNOM 0.4.3 C backend, it consumes 1392 ms
The document says that replacing c backend with CMSIS would bring 5 times speed-up, however, the performance is similar according to my test. What's the reason? NNOM updated or I didn't set CMSIS macros correctly?

[majianjia]

Probably you havent enable CMSIS's NN acceleration, i.e. you are running CMSIS on their C backend instead of SIMD assemblys.
You may check CMSIS instruction or the note under HWC format

[bfs18]

UPDATE: When -Ofast is added, using CMSIS 5.9.0 backend, reduces to 369 ms.

Hi Jia, thanks for your advice. I add

ARM_MATH_DSP,ARM_MATH_CM7,__FPU_PRESENT=1 

using CMSIS 5.9.0 backend, reduces to 1055 ms.
I used the rt-thread qemu-vexpress-a9 bsp. Is this normal?

Probably you havent enable CMSIS's NN acceleration, i.e. you are running CMSIS on their C backend instead of SIMD assemblys. You may check CMSIS instruction or the note under HWC format