This is both a feature and an optimization.
Feature:
Adjustable size of the internal storage in esp_event queue, currently
used by ISR posting, as they wont be able to make a malloc.
Optimization:
When non-isr is posting an event, use the inernal storage in the struct
instead of always allocating a new heap for the data. Most events in
esp-idf only contains a few bytes event information, and we have that
allocation payed for anyway.
This solved in a big part our memory fragmentation issue, as events
happens freqvently and used to create small memory allocations for just
4 bytes, and then in the event handler we usually allocated a bigger
chunk of heap for our feature. When returning from the event handler,
the 4 byte allocation was freed, leaving a hole in the heap.
Merges: https://github.com/espressif/esp-idf/pull/17797
Guillaume Souchere
Jimmy Wennlund
Roland Dobai
Renz Christian Bagaporo