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Always create global BufferPool at startup using 80% of memory and limit reservations to 80% of query memory (same as BufferedBlockMgr). The query's initial reservation is computed in the planner, claimed centrally (managed by the InitialReservations class) and distributed to query operators from there. min_spillable_buffer_size and default_spillable_buffer_size query options control the buffer size that the planner selects for spilling operators. Port ExecNodes to use BufferPool: * Each ExecNode has to claim its reservation during Open() * Port Sorter to use BufferPool. * Switch from BufferedTupleStream to BufferedTupleStreamV2 * Port HashTable to use BufferPool via a Suballocator. This also makes PAGG memory consumption more efficient (avoid wasting buffers) and improve the spilling algorithm: * Allow preaggs to execute with 0 reservation - if streams and hash tables cannot be allocated, it will pass through rows. * Halve the buffer requirement for spilling aggs - avoid allocating buffers for aggregated and unaggregated streams simultaneously. * Rebuild spilled partitions instead of repartitioning (IMPALA-2708) TODO in follow-up patches: * Rename BufferedTupleStreamV2 to BufferedTupleStream * Implement max_row_size query option. Testing: * Updated tests to reflect new memory requirements Change-Id: I7fc7fe1c04e9dfb1a0c749fb56a5e0f2bf9c6c3e Reviewed-on: http://gerrit.cloudera.org:8080/5801 Reviewed-by: Tim Armstrong <tarmstrong@cloudera.com> Tested-by: Impala Public Jenkins