* If USE_MPROTECT_SNAPSHOT=2, then snapshot by tuned mmap() algorithm
* If USE_MPROTECT_SNAPSHOT=1, then snapshot by using mmap() and mprotect()
* If USE_MPROTECT_SNAPSHOT=0, then snapshot by using fork() */
* If USE_MPROTECT_SNAPSHOT=2, then snapshot by tuned mmap() algorithm
* If USE_MPROTECT_SNAPSHOT=1, then snapshot by using mmap() and mprotect()
* If USE_MPROTECT_SNAPSHOT=0, then snapshot by using fork() */