The INNODB_CMPMEM and
INNODB_CMPMEM_RESET tables contain status
information on compressed pages within the
InnoDB buffer pool.
Table 20.2. 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. |
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. |
Notes:
Use these tables to measure the effectiveness of
InnoDBtable compression in your database. For usage information, see Section 13.7.6.1.3, “Using the Compression Information Schema Tables”.