Mysql use High CPU

[L0gRuS]

Good day!

After installed new cacti in x64 centos 6.0 i have problem with CPU. (6G RAM 4 CPU) All time mysql use CPU from 300% to 390%

top - 14:32:30 up 3 days, 21:03, 3 users, load average: 30.17, 28.02, 27.80
Tasks: 156 total, 2 running, 154 sleeping, 0 stopped, 0 zombie
Cpu(s): 62.4%us, 37.1%sy, 0.0%ni, 0.4%id, 0.0%wa, 0.0%hi, 0.1%si, 0.0%st
Mem: 6126156k total, 4193012k used, 1933144k free, 107616k buffers
Swap: 1023992k total, 4724k used, 1019268k free, 2821808k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1132 mysql 20 0 3098m 309m 4368 S 388.2 5.2 20132:46 mysqld

I think is not good.

techinfo from cacti in file.

mysql conf

[root@cacti ~]# cat /etc/my.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
max_heap_table_size = 4G
#max_allowed_packet=32MB
#key_buffer=1024MB
#set-variable = max_connections=500
#set-variable = max_user_connections = 300

max_allowed_packet = 128M
sort_buffer_size = 512M
max_connections=500
#query_cache_size = 512M
#query_cache_limit = 512M
query-cache-type = 2
table_cache = 80
thread_cache_size=8
key_buffer_size = 512M
read_buffer_size=128M
read_rnd_buffer_size=128M
myisam_sort_buffer_size=128M


[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
set-varialbe = max_allowed_packet=16M

[isamchk]
set-varialbe = key_buffer = 512M
set-varialbe = sort_buffer = 512M
set-varialbe = read_buffer = 4M
set-variale - write_buffer = 4M

mysql info from phpmyadmin in file

How i can reduce CPU usage?