Android Memory Allocator - Does memory need to be contiguous?

Does free heap space have to be contiguous for gralloc() calls to succeed? Or can gralloc(开发者_JAVA百科) return sparse free heap segments to satisfy a request? i.e. heap fragmentation

I'd say that's up to the UMP device driver (which Gralloc merely interfaces with), but could be wrong. The driver/hardware may or may not have a way to map non contiguous UMP memory pages into a seemingly contiguous CPU address space. Does that make sense?