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MySQL 5.5 Reference Manual  /  ...  /  The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables

21.28.5 The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables

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

Table 21.5 Columns of INNODB_CMPMEM and INNODB_CMPMEM_RESET

Column name Description
PAGE_SIZE 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 Number of blocks of the size PAGE_SIZE that are currently in use.
PAGES_FREE Number of blocks of the 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 Number of times a block of the 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 table INNODB_CMPMEM_RESET resets this count.
RELOCATION_TIME Total time in microseconds spent in relocating blocks of the 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: 9043
          pages_free: 1
      relocation_ops: 2457
     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:


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