key_buffer_size指定索引缓冲区的大小，它决定索引处理的速度，尤其是索引读的速度。一般我们设为16M,实际上稍微大一点的站点 这个数字是远远不够的，通过检查状态值Key_read_requests和Key_reads,可以知道 key_buffer_size设置是否合理。比例key_reads / key_read_requests应该尽可能的低，至少是1:100，1:1000更好（上述状态值可以使用SHOW STATUS LIKE ‘key_read%'获得）。 或者如果你装了phpmyadmin 可以通过服务器运行状态看到,笔者推荐用phpmyadmin管理mysql，以下的状态值都是本人通过phpmyadmin获得的实例分析:
table_cache 指定表高速缓存的大小。每当MySQL访问一个表时，如果在表缓冲区中还有空间，该表就被打开并放入其中，这样可以更快地访问表内容。通过检查峰值时间的状态值Open_tables和Opened_tables，可以决定是否需要增加table_cache的值。如果你发现open_tables等于 table_cache，并且opened_tables在不断增长，那么你就需要增加table_cache的值了（上述状态值可以使用SHOW STATUS LIKE ‘Open%tables'获得）。注意，不能盲目地把table_cache设置成很大的值。如果设置得太高，可能会造成文件描述符不足，从而造成性能不稳定或者连接失败。
# Example MySQL config file for medium systems. # # 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) # # You can copy this file to # /etc/my.cnf to set global options, # mysql-data-dir/my.cnf to set server-specific options (in this # installation this directory is /var/lib/mysql) or # ~/.my.cnf to set user-specific options. # # 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 = /tmp/mysql.sock #socket = /var/lib/mysql/mysql.sock # Here follows entries for some specific programs
# The MySQL server [mysqld] port = 3306 socket = /tmp/mysql.sock #socket = /var/lib/mysql/mysql.sock skip-locking key_buffer = 128M max_allowed_packet = 1M table_cache = 256 sort_buffer_size = 1M net_buffer_length = 16K myisam_sort_buffer_size = 1M max_connections=120 #addnew config wait_timeout =120 back_log=100 read_buffer_size = 1M thread_cache=32 skip-innodb skip-bdb skip-name-resolve join_buffer_size=512k query_cache_size = 32M interactive_timeout=120 long_query_time=10 log_slow_queries= /usr/local/mysql4/logs/slow_query.log query_cache_type= 1 # Try number of CPU's*2 for thread_concurrency thread_concurrency = 4
#end new config # 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
# 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=, MASTER_PORT=, # MASTER_USER=, MASTER_PASSWORD= ; # # where you replace , , by quoted strings and # 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 = # # The username the slave will use for authentication when connecting # to the master - required #master-user = # # The password the slave will authenticate with when connecting to # the master - required #master-password = # # The port the master is listening on. # optional - defaults to 3306 #master-port = # # binary logging - not required for slaves, but recommended #log-bin
# Point the following paths to different dedicated disks #tmpdir = /tmp/ #log-update = /path-to-dedicated-directory/hostname
# Uncomment the following if you are using BDB tables #bdb_cache_size = 4M #bdb_max_lock = 10000
# 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/ #innodb_log_arch_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 = 16M #innodb_additional_mem_pool_size = 2M # Set .._log_file_size to 25 % of buffer pool size #innodb_log_file_size = 5M #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
优化table_cachetable_cache指定表高速缓存的大小。每当MySQL访问一个表时，如果在表缓冲区中还有空间，该表就被打开并放入其中，这样可以更快地访问表内容。通过检查峰值时间的状态值Open_tables和Opened_tables，可以决定是否需要增加 table_cache的值。如果你发现open_tables等于table_cache，并且opened_tables在不断增长，那么你就需要增加table_cache的值了（上述状态值可以使用SHOW STATUS LIKE ‘Open%tables'获得）。注意，不能盲目地把table_cache设置成很大的值。如果设置得太高，可能会造成文件描述符不足，从而造成性能不稳定或者连接失败。对于有1G内存的机器，推荐值是128－256。
