Optimize MySQL performance with mysqltuner

Tuesday, December 22, 2009 posted by Till

The following tutorial describes the steps to optimize the performance of a MySQL database with the mysqltuner script.

Login to your server on the shell, then execute the following commands:

Download the mysqltuner script:

cd /usr/local/bin
wget http://mysqltuner.pl/mysqltuner.pl
chmod +x mysqltuner.pl

Run mysqltuner


Then enter root as username and the mysql root password.

You will get a output similar to this:

root@v221:/usr/local/bin# /usr/local/bin/mysqltuner.pl

>>  MySQLTuner 1.0.1 - Major Hayden <major@mhtx.net>
>>  Bug reports, feature requests, and downloads at http://mysqltuner.com/
>>  Run with '--help' for additional options and output filtering
Please enter your MySQL administrative login: root
Please enter your MySQL administrative password:

-------- General Statistics --------------------------------------------------
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.0.51a-24+lenny2
[!!] Switch to 64-bit OS - MySQL cannot currently use all of your RAM

-------- Storage Engine Statistics -------------------------------------------
[--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster
[--] Data in MyISAM tables: 26M (Tables: 215)
[!!] InnoDB is enabled but isn't being used
[!!] Total fragmented tables: 33

-------- Performance Metrics -------------------------------------------------
[--] Up for: 96d 23h 3m 41s (10M q [1.239 qps], 686K conn, TX: 701M, RX: 1B)
[--] Reads / Writes: 44% / 56%
[--] Total buffers: 58.0M global + 2.6M per thread (100 max threads)
[OK] Maximum possible memory usage: 320.5M (12% of installed RAM)
[OK] Slow queries: 0% (20/10M)
[OK] Highest usage of available connections: 33% (33/100)
[OK] Key buffer size / total MyISAM indexes: 16.0M/8.5M
[OK] Key buffer hit rate: 99.9% (57M cached / 30K reads)
[OK] Query cache efficiency: 78.6% (5M cached / 6M selects)
[!!] Query cache prunes per day: 483
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 408K sorts)
[!!] Temporary tables created on disk: 36% (269K on disk / 745K total)
[OK] Thread cache hit rate: 99% (427 created / 686K connections)
[!!] Table cache hit rate: 2% (64 open / 3K opened)
[OK] Open file limit used: 11% (120/1K)
[OK] Table locks acquired immediately: 99% (3M immediate / 3M locks)

-------- Recommendations -----------------------------------------------------
General recommendations:
Add skip-innodb to MySQL configuration to disable InnoDB
Run OPTIMIZE TABLE to defragment tables for better performance
Enable the slow query log to troubleshoot bad queries
When making adjustments, make tmp_table_size/max_heap_table_size equal
Reduce your SELECT DISTINCT queries without LIMIT clauses
Increase table_cache gradually to avoid file descriptor limits
Variables to adjust:
query_cache_size (> 16M)
tmp_table_size (> 32M)
max_heap_table_size (> 16M)
table_cache (> 64)

The script recommends to adjust or add the following variables in the mysql my.cnf file. The location of my.cnf is normally /etc/my.cnf or /etc/mysql/my.cnf depending on the Linux distribution that is installed on your server.

Open the my.cnf file:

vi /etc/mysql/my.cnf

and increase or set the variables in the [mysqld] section of the file. Mine looks now like this:

# * Basic Settings
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /var/lib/mysql
tmpdir          = /tmp
language        = /usr/share/mysql/english
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address            =
# * Fine Tuning
key_buffer              = 16M
max_allowed_packet      = 16M
thread_stack            = 128K
thread_cache_size       = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover          = BACKUP
#max_connections        = 100
table_cache            = 128
#thread_concurrency     = 10
# * Query Cache Configuration
query_cache_limit       = 1M

query_cache_size        = 32M
tmp_table_sizee        = 64M
max_heap_table_sizee        = 32M

Then save the file and restart mysql. After a few hours, rerun mysqltuner and check again if the values are fine now or if the have to be increased to a higher value.

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2 Responses to “Optimize MySQL performance with mysqltuner”

  1. Mauricio says:

    i did run this, and fixed the errors on the script, but the command service mysqld restart did not could start again the db, what could happen?

  2. Mauricio says:

    got it, i used, for example, 1.6gb on one line, changed it by mb
    I have 17gb of ram, which one can be my best config for high traffic? i would like to have an idea in case i change my amount of ram

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