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25.39.6 The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables

Contents

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

  1. mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_CMPMEM\G
  2. *************************** 1. row ***************************
  3.            page_size: 1024
  4. buffer_pool_instance: 0
  5.           pages_used: 0
  6.           pages_free: 0
  7.       relocation_ops: 0
  8.      relocation_time: 0
  9. *************************** 2. row ***************************
  10.            page_size: 2048
  11. buffer_pool_instance: 0
  12.           pages_used: 0
  13.           pages_free: 0
  14.       relocation_ops: 0
  15.      relocation_time: 0
  16. *************************** 3. row ***************************
  17.            page_size: 4096
  18. buffer_pool_instance: 0
  19.           pages_used: 0
  20.           pages_free: 0
  21.       relocation_ops: 0
  22.      relocation_time: 0
  23. *************************** 4. row ***************************
  24.            page_size: 8192
  25. buffer_pool_instance: 0
  26.           pages_used: 7673
  27.           pages_free: 15
  28.       relocation_ops: 4638
  29.      relocation_time: 0
  30. *************************** 5. row ***************************
  31.            page_size: 16384
  32. buffer_pool_instance: 0
  33.           pages_used: 0
  34.           pages_free: 0
  35.       relocation_ops: 0
  36.      relocation_time: 0

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Document created the 26/06/2006, last modified the 26/10/2018
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References

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