There are two pairs of InnoDB
INFORMATION_SCHEMA tables about compression
that can provide insight into how well compression is working
overall:
INNODB_CMP and
INNODB_CMP_RESET
contain information about the number of compression operations
and the amount of time spent performing compression.
INNODB_CMPMEM and
INNODB_CMP_RESET
contain information about the way memory is allocated for
compression.