Performance Schema Summary Tables •If a memory allocation operation was instrumented, the corresponding free operation is instrumented, regardless of the current instrument or thread enabled status. •If a memory allocation operation was not instrumented, the corresponding free operation is not instrumented, regardless of the current instrument or thread enabled status. • COUNT_ALLOC : Increased by 1 • CURRENT_COUNT_USED : Increased by 1 • HIGH_COUNT_USED : Increased if  CURRENT_COUNT_USED  is a new maximum • SUM_NUMBER_OF_BYTES_ALLOC : Increased by  N • CURRENT_NUMBER_OF_BYTES_USED : Increased by  N • HIGH_NUMBER_OF_BYTES_USED : Increased if  CURRENT_NUMBER_OF_BYTES_USED  is a new maximum • COUNT_FREE : Increased by 1 • CURRENT_COUNT_USED : Decreased by 1 • LOW_COUNT_USED : Decreased if  CURRENT_COUNT_USED  is a new minimum • SUM_NUMBER_OF_BYTES_FREE : Increased by  N • CURRENT_NUMBER_OF_BYTES_USED : Decreased by  N • LOW_NUMBER_OF_BYTES_USED : Decreased if  CURRENT_NUMBER_OF_BYTES_USED  is a new minimum • LOW_COUNT_USED  and  LOW_NUMBER_OF_BYTES_USED  are lower estimates. The value reported by the Performance Schema is guaranteed to be less than or equal to the lowest count or size of memory effectively used at runtime. • HIGH_COUNT_USED  and  HIGH_NUMBER_OF_BYTES_USED  are higher estimates. The value reported by the Performance Schema is guaranteed to be greater than or equal to the highest count or size of memory effectively used at runtime. Thread 2 uses memory in the range from 10MB to 12MB during execution, as reported likewise. Thread 1 uses memory in the range from 1MB to 2MB during execution, as reported by the  LOW_NUMBER_OF_BYTES_USED  and  HIGH_NUMBER_OF_BYTES_USED  columns of the memory_summary_by_thread_by_event_name  table. Here is an example of estimate computation; but note that estimate implementation is subject to change: For lower estimates in summary tables other than  memory_summary_global_by_event_name , it is possible for values to go negative if memory ownership is transferred between threads. For higher-level aggregates (global, by account, by user, by host), the same rules apply as expected for low and high water marks. When an instrumented memory block is deallocated, the Performance Schema makes these updates to memory summary table columns: When an instrumented memory block of size  N  is allocated, the Performance Schema makes these updates to memory summary table columns: For the per-thread statistics, the following rules apply. 5073