mysql 5.6、5.7默认启动占用内存400多M，如果是vps等小内存应用，mysql内存占用率明显偏高,将会导致崩溃，mysql会自动停止。
编辑/etc/my.cnf文件在[mysqld]下增加或修改如下参数

performance_schema_max_table_instances = 200

table_definition_cache = 100

table_open_cache = 100。

这个三个参数，调低值后内存能明显减小，现在mysql使用内存约60MB左右，就大大降低默认使用的内存。

进一步调整参数

innodb_buffer_pool_size=2M

这个三个参数可以调小。 再进一步调整： mysql 5.6默认启用performance_schema，占用很多内存，可以禁用。

完整配置文件如下，内存占用到22M

我的mysql配置如下，如果你使用的centos6 64位，并且是yum安装的（一键脚本)可以自己按照如下照抄，我的是centos6 64位系统

先ssh登录服务器或VPS，在vi /etc/my.cnf

# For advice on how to change settings please see

# http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html

[mysqld]

#

# Remove leading # and set to the amount of RAM for the most important data

# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.

# innodb_buffer_pool_size = 128M

#

# Remove leading # to turn on a very important data integrity option: logging

# changes to the binary log between backups.

# log_bin

#

# Remove leading # to set options mainly useful for reporting servers.

# The server defaults are faster for transactions and fast SELECTs.

# Adjust sizes as needed, experiment to find the optimal values.

# join_buffer_size = 128M

# sort_buffer_size = 2M

# read_rnd_buffer_size = 2M

datadir=/var/lib/mysql

socket=/var/lib/mysql/mysql.sock

#symbolic-links=0

skip-external-locking

key_buffer_size = 8M

max_allowed_packet = 1M

table_open_cache = 4

sort_buffer_size = 64K

read_buffer_size = 256K

read_rnd_buffer_size = 256K

net_buffer_length = 2K

thread_stack = 240K

#innodb_use_native_aio = 0

innodb_buffer_pool_size=2M

performance_schema_max_table_instances=50

table_definition_cache=50

table_open_cache=32

max_connections=50

max_user_connections=35

wait_timeout=10

interactive_timeout=15

long_query_time=5

# Disabling symbolic-links is recommended to prevent assorted security risks

symbolic-links=0

# Recommended in standard MySQL setup

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

[mysqld_safe]

log-error=/var/log/mysqld.log

pid-file=/var/run/mysqld/mysqld.pid

默认值如下：

performance_schema_max_table_instances 12500

table_definition_cache 1400

table_open_cache 2000