A detailed introduction to how to optimize MySQL in Linux

This article mainly introduces the relevant information about MySQL optimization examples in Linux. Friends who need it can refer to

Linux. Detailed explanation of MySQL optimization examples

vim /etc/my.cnf The following only lists the contents of the [mysqld] paragraph in the my.cnf file. The contents of other paragraphs have little impact on the running performance of MySQL, so for the time being neglect.

[mysqld]
port = 3306
serverid = 1
socket = /tmp/mysql.sock
skip-locking

Avoid MySQL's external locking, reduce the chance of errors and enhance stability.

skip-name-resolve

Prohibit MySQL from performing DNS resolution on external connections. Using this option can eliminate the time MySQL spends on DNS resolution. However, it should be noted that if this option is turned on, all remote host connection authorizations must use IP addresses, otherwise MySQL will not be able to process connection requests normally!

back_log = 384

The value of the back_log parameter indicates how many requests can be stored in the stack in a short period of time before MySQL temporarily stops responding to new requests. If the system has many connections in a short period of time, you need to increase the value of this parameter, which specifies the size of the listening queue for incoming TCP/IP connections. Different operating systems have their own limits on this queue size. Attempting to set back_log higher than your operating system's limit will have no effect. The default value is 50. For Linux systems, it is recommended to set it to an integer less than 512.

key_buffer_size = 256M

key_buffer_size specifies the buffer size used for indexing, increase it for better index processing performance. For servers with memory around 4GB, this parameter can be set to 256M or 384M. Note: Setting this parameter value too large will reduce the overall efficiency of the server!

max_allowed_packet = 4M
thread_stack = 256K
table_cache = 128K
sort_buffer_size = 6M

QueryThe buffer size that can be used during sorting. Note: The allocated memory corresponding to this parameter is exclusive to each connection. If there are 100 connections, then the total allocated sort buffer size is 100 × 6 = 600MB. Therefore, it is recommended to set it to 6-8M for a server with a memory of about 4GB.

read_buffer_size = 4M

The buffer size that can be used by read query operations. Like sort_buffer_size, the allocated memory corresponding to this parameter is also exclusive to each connection.

join_buffer_size = 8M

Union queryThe buffer size that can be used for the operation is the same as sort_buffer_size. The allocated memory corresponding to this parameter is also exclusive to each connection.

myisam_sort_buffer_size = 64M
table_cache = 512
thread_cache_size = 64
query_cache_size = 64M

Specify the size of the MySQL query buffer. It can be observed in the MySQL console. If the value of Qcache_lowmem_prunes is very large, it indicates that there is often insufficient buffering. If the value of Qcache_hits is very large, it indicates that the query buffer is used very frequently. If the value is small, it will affect the efficiency. Then You can consider not querying the cache; Qcache_free_blocks, if the value is very large, it indicates that there are many fragments in the buffer.

tmp_table_size = 256M
max_connections = 768

Specify the maximum number of connection processes allowed by MySQL. If Too ManyConnections error messages often appear when accessing the forum, you need to increase the value of this parameter.

max_connect_errors = 10000000
wait_timeout = 10

Specify the maximum connection time for a request. For servers with about 4GB of memory, it can be set to 5-10.

thread_concurrency = 8

The value of this parameter is the number of server logical CPUs*2. In this example, the server has 2 physical CPUs, and each physical CPU supports H.T hyper-threading, so the actual value is 4*2 =8

skip-networking

Turning on this option can completely turn off MySQL's TCP/IP connection. If the WEB server accesses the MySQL database server through a remote connection, do not turn on this option! Otherwise, the normal connection will not be possible!

table_cache=1024

The larger the physical memory, the larger the setting. The default is 2402, adjust to 512-1024 for the best

innodb_additional_mem_pool_size=4M

The default is 2M

innodb_flush_log_at_trx_commit=1

Set to 0 is to wait until innodb_log_buffer_size will be stored uniformly after the queue is full. The default is 1

innodb_log_buffer_size=2M

The default is 1M

innodb_thread_concurrency=8

Set it to how many CPUs your server has. It is recommended that the default is generally 8

key_buffer_size=256M
#默认为218，调到128最佳
tmp_table_size=64M         
#默认为16M，调到64-256最挂
read_buffer_size=4M        
#默认为64K
read_rnd_buffer_size=16M    
#默认为256K
sort_buffer_size=32M       
#默认为256K
thread_cache_size=120     
#默认为60
query_cache_size=32M

It is worth noting:

Many situations require specific analysis

1. If Key_reads is too large, my should be Increase the Key_buffer_size in .cnf and keep Key_reads/Key_read_requests at least 1/100. The smaller the better.

2. If Qcache_lowmem_prunes is very large, increase the value of Query_cache_size.

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