[popcornmix]

I'm not sure how low we want to go with MALLOC_MMAP_THRESHOLD_ - a value of 8192 might be a usable value. I feel that going as low as 1024 might result in an excessive number of chunks for no real advantage. But that's all a bit finger-in-the-air.

  
Be aware that mallocs above the threshold are much more expensive (in arm CPU time), so a high threshold is beneficial for performance.
When John's back I'll check what ram gets dynamically allocated and whether any large allocations can be "pooled".

Feel free to add MALLOC_MMAP_THRESHOLD_ to subsequent builds for further testing, but personally I'd favour a slightly larger value (32K/64K) for performance.
But I guess having the smaller value for testing purposes may be interesting (if no one notices the difference then maybe it's not important).