[SPARK-11389][CORE] Add support for off-heap memory to MemoryManager
In order to lay the groundwork for proper off-heap memory support in SQL /
Tungsten, we need to extend our MemoryManager to perform bookkeeping for
off-heap memory.
## User-facing changes
This PR introduces a new
[SPARK-11389][CORE] Add support for off-heap memory to MemoryManager
In order to lay the groundwork for proper off-heap memory support in SQL /
Tungsten, we need to extend our MemoryManager to perform bookkeeping for
off-heap memory.
## User-facing changes
This PR introduces a new
