發現一篇不錯的優化MySQL的文章http://blog.haohtml.com/archives/4248，看完記錄一下
黑色的表示查詢配置和狀態，綠色的表示優化原則
清除狀態 FLUSH STATUS;
慢查詢
show variables like '%slow%';
show global status like '%slow%';
連接數
show variables like 'max_connections';
show global status like'Max_used_connections';
Max_used_connections / max_connections * 100% ≈ 85%
Key_buffer_size--MyISAM
show variables like 'key_buffer_size';
show global status like 'key_read%';
key_cache_miss_rate＝ Key_reads / Key_read_requests * 100% <
show global status like'key_blocks_u%';
Key_blocks_used / (Key_blocks_unused +Key_blocks_used) * 100% ≈ 80%
臨時表
show variables where Variable_name in('tmp_table_size', 'max_heap_table_size');
show global status like 'created_tmp%';
Created_tmp_disk_tables / Created_tmp_tables * 100% <= 25%
Open Table情況
show variables like 'table_cache';à show variables like 'table_open_cache';
show global status like 'open%tables%';
Open_tables / Opened_tables * 100% >= 85%
Open_tables / table_cache * 100% <= 95%
進程使用情況
show variables like'thread_cache_size';
show global status like 'Thread%';
Threads_created值不應過大，否則應增加thread_cache_size
查詢緩存
show variables like 'query_cache%';
show global status like 'qcache%';
查詢緩存碎片率 = Qcache_free_blocks /Qcache_total_blocks * 100% < 20%
查詢緩存利用率 = (query_cache_size - Qcache_free_memory)/ query_cache_size * 100%à 25%-80%
查詢緩存命中率 = (Qcache_hits - Qcache_inserts) /Qcache_hits * 100% >
排序使用情況
show variables like 'Sort_buffer_size';
show global status like 'sort%';
Sort_merge_passes <
文件打開數
show variables like 'open_files_limit';
show global status like 'open_files';
Open_files / open_files_limit * 100% <=75％
表鎖情況
show global status like 'table_locks%';
Table_locks_immediate / Table_locks_waited> 5000，最好採用InnoDB引擎，小則MyIASM
表掃描情況
show global status like 'com_select';
show global status like'handler_read%';
表掃描率＝ Handler_read_rnd_next / Com_select <
如果表掃描率超過4000，說明進行了太多表掃描，很有可能索引沒有建好，增加read_buffer_size值會有一些好處，但最好不要超過 8MB。
最後優化後的my.cnf如下
# Example MySQL config file for large systems.
#
# This is for a large system with memory = 512M where the system runs mainly
# MySQL.
#
# MySQL programs look for option files in a set of
# locations which depend on the deployment platform.
# You can copy this option file to one of those
# locations. For information about these locations, see:
# http://dev.mysql.com/doc/mysql/en/option-files.html
#
# In this file, you can use all long options that a program supports.
# If you want to know which options a program supports, run the program
# with the "--help" option.
# The following options will be passed to all MySQL clients
[client]
#password = your_password
port = 3306
socket = /var/lib/mysql/mysql.sock
# Here follows entries for some specific programs
# The MySQL server
[mysqld]
port = 3306
socket = /var/lib/mysql/mysql.sock
skip-locking
key_buffer_size = 16M
max_allowed_packet = 1M
table_open_cache = 256
sort_buffer_size = 4M
read_buffer_size = 4M
read_rnd_buffer_size = 8M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size = 32M
lower_case_table_names = 1
# Try number of CPU's*2 for thread_concurrency
thread_concurrency = 8
# Don't listen on a TCP/IP port at all. This can be a security enhancement,
# if all processes that need to connect to mysqld run on the same host.
# All interaction with mysqld must be made via Unix sockets or named pipes.
# Note that using this option without enabling named pipes on Windows
# (via the "enable-named-pipe" option) will render mysqld useless!
#
#skip-networking
# Replication Master Server (default)
# binary logging is required for replication
log-bin=mysql-bin
# binary logging format - mixed recommended
binlog_format=mixed
# required unique id between 1 and 2^32 - 1
# defaults to 1 if master-host is not set
# but will not function as a master if omitted
server-id = 1
# Replication Slave (comment out master section to use this)
#
# To configure this host as a replication slave, you can choose between
# two methods :
#
# 1) Use the CHANGE MASTER TO command (fully described in our manual) -
# the syntax is:
#
# CHANGE MASTER TO MASTER_HOST=<host>, MASTER_PORT=<port>,
# MASTER_USER=<user>, MASTER_PASSWORD=<password> ;
#
# where you replace <host>, <user>, <password> by quoted strings and
# <port> by the master's port number (3306 by default).
#
# Example:
#
# CHANGE MASTER TO MASTER_HOST='125.564.12.1', MASTER_PORT=3306,
# MASTER_USER='joe', MASTER_PASSWORD='secret';
#
# OR
#
# 2) Set the variables below. However, in case you choose this method, then
# start replication for the first time (even unsuccessfully, for example
# if you mistyped the password in master-password and the slave fails to
# connect), the slave will create a master.info file, and any later
# change in this file to the variables' values below will be ignored and
# overridden by the content of the master.info file, unless you shutdown
# the slave server, delete master.info and restart the slaver server.
# For that reason, you may want to leave the lines below untouched
# (commented) and instead use CHANGE MASTER TO (see above)
#
# required unique id between 2 and 2^32 - 1
# (and different from the master)
# defaults to 2 if master-host is set
# but will not function as a slave if omitted
#server-id = 2
#
# The replication master for this slave - required
#master-host = <hostname>
#
# The username the slave will use for authentication when connecting
# to the master - required
#master-user = <username>
#
# The password the slave will authenticate with when connecting to
# the master - required
#master-password = <password>
#
# The port the master is listening on.
# optional - defaults to 3306
#master-port = <port>
#
# binary logging - not required for slaves, but recommended
#log-bin=mysql-bin
# Uncomment the following if you are using InnoDB tables
innodb_data_home_dir = /var/lib/mysql
innodb_data_file_path = ibdata1:10M:autoextend
innodb_log_group_home_dir = /var/lib/mysql
# You can set .._buffer_pool_size up to 50 - 80 %
# of RAM but beware of setting memory usage too high
innodb_buffer_pool_size = 256M
innodb_additional_mem_pool_size = 20M
# Set .._log_file_size to 25 % of buffer pool size
innodb_log_file_size = 64M
innodb_log_buffer_size = 8M
innodb_flush_log_at_trx_commit = 1
innodb_lock_wait_timeout = 50
[mysqldump]
quick
max_allowed_packet = 16M
[mysql]
no-auto-rehash
# Remove the next comment character if you are not familiar with SQL
#safe-updates
[myisamchk]
key_buffer_size = 128M
sort_buffer_size = 128M
read_buffer = 2M
write_buffer = 2M
[mysqlhotcopy]
interactive-timeout