Sometimes php applications are not tuned up properly. In that case we can track the mysql queries running at very slow speed.
To do this
Edit /etc/init.d/mysql
$bindir/mysqld_safe –datadir=$datadir –pid-file=$pid_file >/dev/null 2>&1 &
Add –log-slow-queries=/var/log/slow-queries.log to above line as below.
$bindir/mysqld_safe –datadir=$datadir –pid-file=$pid_file –log-slow-queries=/var/log/slow-queries.log
>/dev/null 2>&1 &
