Maximum size of WASM module

[jiayihu]

The WASM standard defines memory pages of 64KB so at least 1 must be supported. At the same time it cannot support more than 1 in STM32F407 where at most 128KB of RAM is available.

Memory estimates are:

• 4KB reserved for the system runtime stack
• The rest is heap:
  • 64KB for the module memory
  • 4KB for the WASM value stack, also called operand stack
  • The remaining must be used to receive the WASM module from the UDP socket and for parsing the module

A possible solution is to move the stack to CCRAM, where additional 64KB are available. In that case UDP socket buffer can also be moved to the stack, allocating a static buffer with sufficient upper bound.

Resources:

• Make use of the 64k CCM