MySQL 占用大量资源，导致负载高达 65

双核 2G 内存， MySQL 经常占用 180%以上的 CPU 资源，导致系统负载奔 70 。站点直接 502 。
http://www.repaik.com/mysql.jpg
(imgur 上传老是出错，翻墙都不行）
以下是我的 My.conf 配置，求大神分析:

[client]
port = 3306
socket = /tmp/mysql.sock
[mysqld]
port = 3306
socket = /tmp/mysql.sock
skip-external-locking
skip-networking
loose-skip-innodb
key_buffer_size = 256M
max_allowed_packet = 1M
table_open_cache = 256
sort_buffer_size = 1M
read_buffer_size = 1M
read_rnd_buffer_size = 4M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size= 16M
thread_concurrency = 8
max_connections = 400
wait_timeout = 30
interactive_timeout = 30
max_connect_errors = 9
long_query_time = 1
tmp_table_size = 16M
#log-bin=mysql-bin
#binlog_format=mixed
#server-id = 1
[mysqldump]
quick
max_allowed_packet = 16M
[mysql]
no-auto-rehash
[myisamchk]
key_buffer_size = 128M
sort_buffer_size = 128M
read_buffer = 2M
write_buffer = 2M
[mysqlhotcopy]
interactive-timeout