[mysqld]
port = {blah}
socket = /var/lib/mysql/mysql.sock
skip-locking
key_buffer = 128M
max_allowed_packet = 1M
table_cache=1024
thread_cache_size=4
max_connections=256
max_user_connections=32
join_buffer_size=2M
sort_buffer_size = 2M
read_buffer_size = 2M
read_rnd_buffer_size = 4M
query_cache_size=512M
query_cache_type=1
tmp_table_size=128M
max_heap_table_size=128M
skip-bdb
# skip-innodb
[mysqldump]
quick
max_allowed_packet = 16M
[mysql]
no-auto-rehash
#safe-updates
[isamchk]
key_buffer = 8M
sort_buffer_size = 8M
[myisamchk]
key_buffer = 8M
sort_buffer_size = 8M
[mysqlhotcopy]
interactive-timeout
Don't use InnoDB engine, its shit. Use MyISAM engine :D
Also, if the problem still prevails then you no option other than move the site to a separate VPS.
are you pinging new topics to a huge list of sites? iv read through the thread and its the only thing i can think of. it makes sense since it only occurs when new topics are posted.
mybe this help
1. Use cache plugin (supercache, w3, etc) tried, no difference
2. define('WP_POST_REVISIONS', false ); Edited that already, when I started blog
3. Optimize my.cnf, calculate using this program https://launchpad.net/mysql-tuning-primer you can see my.cnf