Performance Schema Summary Tables • LOW_COUNT_USED  and  HIGH_COUNT_USED  are reset to  CURRENT_COUNT_USED . • LOW_NUMBER_OF_BYTES_USED  and  HIGH_NUMBER_OF_BYTES_USED  are reset to CURRENT_NUMBER_OF_BYTES_USED . In addition, each memory summary table that is aggregated by account, host, user, or thread is implicitly truncated by truncation of the connection table on which it depends, or truncation of memory_summary_global_by_event_name . For details, see Section 27.12.8, “Performance Schema Connection Tables” . Memory instruments are listed in the  setup_instruments  table and have names of the form memory/ code_area / instrument_name . Memory instrumentation is enabled by default. Instruments named with the prefix  memory/performance_schema/  expose how much memory is allocated for internal buffers in the Performance Schema itself. The  memory/performance_schema/ instruments are built in, always enabled, and cannot be disabled at startup or runtime. Built-in memory instruments are displayed only in the  memory_summary_global_by_event_name  table. To control memory instrumentation state at server startup, use lines like these in your  my.cnf  file: Memory Instrumentation Behavior •Enable: •Disable: •Enable: •Disable: [mysqld] performance-schema-instrument=’memory/%=ON’ [mysqld] performance-schema-instrument=’memory/%=OFF’ To control memory instrumentation state at runtime, update the  ENABLED  column of the relevant instruments in the  setup_instruments  table: For memory instruments, the  TIMED  column in  setup_instruments  is ignored because memory operations are not timed. When a thread in the server executes a memory allocation that has been instrumented, these rules apply: •If the thread is not instrumented or the memory instrument is not enabled, the memory block allocated is not instrumented. •Otherwise (that is, both the thread and the instrument are enabled), the memory block allocated is instrumented. For deallocation, these rules apply: 5072 UPDATE performance_schema.setup_instruments SET ENABLED = ’YES’ WHERE NAME LIKE ’memory/%’; UPDATE performance_schema.setup_instruments SET ENABLED = ’NO’ WHERE NAME LIKE ’memory/%’;