Have the kernel give the leftover memory to the IP stack

[zephyrbot]

Reported by Benjamin Walsh:

The memory left after the kernel image is currently wasted, and the IP stack could make use of it for its buffers. Give that memory to the IP stack if available.

(Imported from Jira ZEP-1065)

[zephyrbot]

by Andy Ross:

Must it be the IP stack? There's recently been a bunch of work commited that reworks the net_buf allocation to make it less generic (i.e. each net_context can have its own pool) and not more, precisely because big users like TCP were stepping on other parts of the subsystem and causing exhaustion.

Maybe what we really want is to put the k_malloc() _HEAP_MEM_POOL memory in "all remaining RAM" instead of making it a fixed size?

[zephyrbot]

by Sharron LIU:

"what we really want" need to be finalized before label "Testable". Thanks.

[zephyrbot]

by Andy Ross:

Whoops, this got caught in a bunch of updated and marked "Code Review" when it wasn't. Move back to in-progress. The way this is working out is that it will use the new "arbitrary block size" feature of the allocator and a little linker work to mark all RAM between the end of the existing segment and the end of physical memory as a single pool to be used by k_malloc/k_free. So, not "IP stack" at all, but because it avoids the fixed size kernel pool it allows apps to choose their own pool sizes freely.

[nashif]

This is too custom and specific, we do need a better approach to deal with left-over memory.