Reply to Weed,
I think so: during the performance of malloc is controlled by the OS. And it is so does the optimization of memory allocation for programs. And OS has more facilities to do this. GC there will be just extra layer.
malloc is not a system call. malloc make systems calls (IIRC mmap) once in a while to ask for more memory to be mapped in but I think that D's GC also works that way.
