Memory hooks

UCX includes the libucm library, which provides methods to intercept events which map and unmap memory to/from the current process. These may be used by transports to optimize their handling of user-allocated memory, for example:

• Maintain memory registration cache (and get notification when cached memory is unmapped)
• Modify the way memory is allocated (e.g hugepages, MAP_PRIVATE vs MAP_SHARED)

libucm API allows registering for the following events:

UCM_EVENT_MMAP	mmap() is called
UCM_EVENT_MUNMAP	munmap() is called
UCM_EVENT_MREMAP	mremap() is called
UCM_EVENT_SHMAT	shmat() is called
UCM_EVENT_SHMDT	shmdt() is called
UCM_EVENT_SBRK	sbrk() is called
UCM_EVENT_VM_MAPPED	memory is mapped to the process
UCM_EVENT_VM_UNMAPPED	memory is unmapped from the process