一般都是my.cnf配置文件的问题
/etc/my.cnf来自以下文件：
如果你的内存≤64M，则复制/usr/local/share/mysql/my-small.cnf为/etc/my.cnf
# This is for a system with little memory (<= 64M) where MySQL is only used
# from time to time and it’s important that the mysqld daemon
# doesn’t use much resources.
如果内存是128M，则复制/usr/local/share/mysql/my-medium.cnf为/etc/my.cnf
# This is for a system with little memory (32M - 64M) where MySQL plays
# an important part, or systems up to 128M where MySQL is used together with
# other programs (such as a web server)
如果内存是512M，则复制/usr/local/share/mysql/my-large.cnf为/etc/my.cnf
# This is for a large system with memory = 512M where the system runs mainly
# MySQL.
如果内存是1-2G，则复制/usr/local/share/mysql/my-huge.cnf为/etc/my.cnf
# This is for a large system with memory of 1G-2G where the system runs mainly
# MySQL.
