High CPU with high volume of INSERT DELAYED

[N An]

Hello

I have some perl code that is pushing custom csv format Apache access_logs from 90 heavily active webservers to a MySQL database server and inserting data into daily tables. I use prepare SQL and INSERT DELAYED, however, I have a consistent 100% CPU usage on the MySQL database server and all the cpu is used by MySQL. The server has 4TB of SAN Array disks attached where this data is stored, 16GB RAM and 8 CPUs running SuSE Linux 11 SP3 and MySQL 5.5.31. I would really appreciate any help in tuning this and reducing the 100% CPU usage. Following is what I have my.cnf:

[client]
port = 3306
socket = /var/lib/mysql/mysql.sock
[mysqld]
port = 3306
socket = /var/lib/mysql/mysql.sock
key_buffer = 3G
max_allowed_packet = 1M
table_cache = 4096
max_connections = 750
sort_buffer_size = 2M
read_buffer_size = 4M
read_rnd_buffer_size = 8M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size = 128M
thread_concurrency = 16
server-id = 1
ignore-builtin-innodb
default-storage-engine = myisam
[safe_mysqld]
log-error=/var/lib/mysql/mysqld.log
[mysqldump]
quick
max_allowed_packet = 16M
[mysql]
no-auto-rehash
[isamchk]
key_buffer = 256M
sort_buffer_size = 256M
read_buffer = 2M
write_buffer = 2M
[myisamchk]
key_buffer = 256M
sort_buffer_size = 256M
read_buffer = 2M
write_buffer = 2M
[mysqlhotcopy]
interactive-timeout


Thanks