InnoDB CPU Spikes

[Sabari girish Viswanathan]

We are facing CPU utilization to increase when a select query is fired against a table having approximately 100million records (on average). This table has InnoDB as its engine. The select query is executed to generate MIS reports.

The cpu utilization of mysqld increases from 1.5% to about 50% till the completion of the query. Being a audit log table the transactions are written to continuously to this table at a rate of 200TPS.

The load average on this machine is 0.3 - 0.6 but when the reports are generated it peaks to 2 - 3.

The reports are generated everyday and have the date in the where clause. Even with an index on the table the cpu utilization does not seem to have major changes.


Hardware
# uname -a
SunOS GATEWAY-SUN2 5.10 Generic_127127-11 sun4u sparc SUNW,Sun-Fire-V490

8GB RAM



My.cnf
# cat my.cnf
[mysqld]
innodb_flush_log_at_trx_commit=2
innodb_doublewrite=0
innodb_buffer_pool_size=1G
innodb_max_dirty_pages_pct=90
datadir=/gateway/mysql/data_dir


Table Defn
mysql> desc tblAuditLog;
+--------------------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------------------+-------------+------+-----+---------+----------------+
| pkAuditLogId | bigint(20) | NO | PRI | NULL | auto_increment |
| fldInvokeId | varchar(6) | YES | | NULL | |
| fldCreatedDate | datetime | YES | | NULL | |
| fldDialogId | varchar(6) | YES | | NULL | |
| fldExternalSystemInfo | varchar(80) | YES | | NULL | |
| fldShortCode | varchar(10) | YES | | NULL | |
| fldRequestTimestamp | datetime | YES | | NULL | |
| fldResponseTimestamp | datetime | YES | | NULL | |
| fldMsisdnnumber | varchar(14) | YES | | NULL | |
| fldESRequesttimestamp | datetime | YES | | NULL | |
| fldESResponsetimestamp | datetime | YES | | NULL | |
| fldEngineName | varchar(10) | YES | | NULL | |
| fldExternalSystem | varchar(50) | YES | | NULL | |
| fldRegionName | varchar(10) | YES | | NULL | |
| fldResponsetype | tinyint(1) | YES | | NULL | |
+--------------------------+-------------+------+-----+---------+----------------+
15 rows in set (0.01 sec)


Any guidance / pointers will be very helpful for me to get out of this problem.

Thanks in advance!