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These two tables have identical contents, but reading from INNODB_CMP_RESET  resets the statistics on compression and uncompression operations. For example, if you archive the output of INNODB_CMP_RESET  every 60 minutes, you see the statistics for each hourly period. If you monitor the output of INNODB_CMP  (making sure never to read INNODB_CMP_RESET ), you see the cumulative statistics since InnoDB was started. 

For the table definition, see Section 26.4.6, “The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables” . 

## 15.15.1.2 INNODB_CMPMEM and INNODB_CMPMEM_RESET 

The INNODB_CMPMEM  and INNODB_CMPMEM_RESET  tables provide status information about compressed pages that reside in the buffer pool. Please consult Section 15.9, “InnoDB Table and Page Compression” for further information on compressed tables and the use of the buffer pool. The INNODB_CMP  and INNODB_CMP_RESET  tables should provide more useful statistics on compression. 

## Internal Details 

InnoDB  uses a buddy allocator system to manage memory allocated to pages of various sizes, from 1KB to 16KB. Each row of the two tables described here corresponds to a single page size. 

The INNODB_CMPMEM  and INNODB_CMPMEM_RESET  tables have identical contents, but reading from INNODB_CMPMEM_RESET  resets the statistics on relocation operations. For example, if every 60 minutes you archived the output of INNODB_CMPMEM_RESET , it would show the hourly statistics. If you never read INNODB_CMPMEM_RESET  and monitored the output of INNODB_CMPMEM  instead, it would show the cumulative statistics since InnoDB  was started. 

For the table definition, see Section 26.4.7, “The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables” . 

## 15.15.1.3 Using the Compression Information Schema Tables 

## Example 15.1 Using the Compression Information Schema Tables 

The following is sample output from a database that contains compressed tables (see Section 15.9, “InnoDB Table and Page Compression” , INNODB_CMP , INNODB_CMP_PER_INDEX , and INNODB_CMPMEM ). 

The following table shows the contents of INFORMATION_SCHEMA.INNODB_CMP  under a light workload. The only compressed page size that the buffer pool contains is 8K. Compressing or uncompressing pages has consumed less than a second since the time the statistics were reset, because the columns COMPRESS_TIME  and UNCOMPRESS_TIME  are zero. 

<img src='content_image/864059.jpg'>

According to INNODB_CMPMEM , there are 6169 compressed 8KB pages in the buffer pool. The only other allocated block size is 64 bytes. The smallest PAGE_SIZE  in INNODB_CMPMEM  is used for block 

