mysql无故重启网站缓慢

最近网站从discuz 2.0升级到3.1后，网站大约每隔12小时左右，会变慢，变得非常慢，然后mysql报错，1040 notconnection
问题是，后台的日志里没有留下错误信息，而且，大约10分钟内，它会自动重启。

下面是日志：

140411 20:50:09 [Warning] Statement may not be safe to log in statement format. Statement: UPDATE pre_common_plugin_luckypostlog SET badtimes = badtimes+1 WHERE uid = '43010' LIMIT 1
140411 20:51:29 [Warning] Statement may not be safe to log in statement format. Statement: UPDATE pre_common_plugin_luckypostlog SET badtimes = badtimes+1 WHERE uid = '43010' LIMIT 1
140411 20:52:02 [Warning] Statement may not be safe to log in statement format. Statement: UPDATE pre_common_plugin_luckypostlog SET badtimes = badtimes+1 WHERE uid = '43010' LIMIT 1
140411 20:58:06 [Warning] Statement may not be safe to log in statement format. Statement: UPDATE pre_common_plugin_luckypostlog SET goodtimes = goodtimes+1 WHERE uid = '21013' LIMIT 1
140411 21:00:29 [Warning] Statement may not be safe to log in statement format. Statement: UPDATE pre_common_plugin_luckypostlog SET badtimes = badtimes+1 WHERE uid = '43953' LIMIT 1
140411 21:02:05 [Warning] Statement may not be safe to log in statement format. Statement: UPDATE pre_common_plugin_luckypostlog SET goodtimes = goodtimes+1 WHERE uid = '43953' LIMIT 1
140411 21:02:30 [Warning] Statement may not be safe to log in statement format. Statement: UPDATE pre_common_plugin_luckypostlog SET goodtimes = goodtimes+1 WHERE uid = '43953' LIMIT 1
140411 21:04:49 [Warning] Statement may not be safe to log in statement format. Statement: UPDATE pre_common_plugin_luckypostlog SET badtimes = badtimes+1 WHERE uid = '43953' LIMIT 1
140411 21:16:12 [Warning] Statement may not be safe to log in statement format. Statement: UPDATE pre_common_plugin_luckypostlog SET goodtimes = goodtimes+1 WHERE uid = '26253' LIMIT 1
140411 21:36:42 [Note] /usr/local/mysql/libexec/mysqld: Normal shutdown

140411 21:36:42 [Note] Event Scheduler: Purging the queue. 0 events
140411 21:36:42 [Note] /usr/local/mysql/libexec/mysqld: Shutdown complete

140411 21:36:42 mysqld_safe mysqld from pid file /usr/local/mysql/var/k130811kd.pid ended
140411 21:36:44 mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/var
140411 21:36:44 [Warning] '--skip-locking' is deprecated and will be removed in a future release. Please use '--skip-external-locking' instead.
140411 21:36:44 [Note] Event Scheduler: Loaded 0 events
140411 21:36:44 [Note] /usr/local/mysql/libexec/mysqld: ready for connections.
Version: '5.1.60-log' socket: '/tmp/mysql.sock' port: 3306 Source distribution

请问如何处理是好。。