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MySQL 5.7 Reference Manual  /  ...  /  The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables

24.32.5 The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables

The INNODB_CMPMEM and INNODB_CMPMEM_RESET tables provide status information on compressed pages within the InnoDB buffer pool.

The INNODB_CMPMEM and INNODB_CMPMEM_RESET tables have these columns:

  • PAGE_SIZE

    The block size in bytes. Each record of this table describes blocks of this size.

  • BUFFER_POOL_INSTANCE

    A unique identifier for the buffer pool instance.

  • PAGES_USED

    The number of blocks of size PAGE_SIZE that are currently in use.

  • PAGES_FREE

    The number of blocks of size PAGE_SIZE that are currently available for allocation. This column shows the external fragmentation in the memory pool. Ideally, these numbers should be at most 1.

  • RELOCATION_OPS

    The number of times a block of size PAGE_SIZE has been relocated. The buddy system can relocate the allocated buddy neighbor of a freed block when it tries to form a bigger freed block. Reading from the INNODB_CMPMEM_RESET table resets this count.

  • RELOCATION_TIME

    The total time in microseconds used for relocating blocks of size PAGE_SIZE. Reading from the table INNODB_CMPMEM_RESET resets this count.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_CMPMEM\G
*************************** 1. row ***************************
           page_size: 1024
buffer_pool_instance: 0
          pages_used: 0
          pages_free: 0
      relocation_ops: 0
     relocation_time: 0
*************************** 2. row ***************************
           page_size: 2048
buffer_pool_instance: 0
          pages_used: 0
          pages_free: 0
      relocation_ops: 0
     relocation_time: 0
*************************** 3. row ***************************
           page_size: 4096
buffer_pool_instance: 0
          pages_used: 0
          pages_free: 0
      relocation_ops: 0
     relocation_time: 0
*************************** 4. row ***************************
           page_size: 8192
buffer_pool_instance: 0
          pages_used: 7673
          pages_free: 15
      relocation_ops: 4638
     relocation_time: 0
*************************** 5. row ***************************
           page_size: 16384
buffer_pool_instance: 0
          pages_used: 0
          pages_free: 0
      relocation_ops: 0
     relocation_time: 0

Notes