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| == MySQL == | | == MySQL == |
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| === Performance Tuning ===
| | [[MySQL#Performance_Tuning | MySQL Performance Tuning]] |
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| '''1. First, Check innodb and myisam settings'''
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| Run the below to get the size of data in INNODB and MYISAM tables:<br />
| | == OOM Killer == |
| <pre>mysql -e 'SELECT SQL_NO_CACHE Engine, count(*) "# of Tables", concat(round(sum(table_rows)/1000,2),"K") "Rows", concat(round(sum(data_length)/(1024*1024),2),"M") "Size of Data", concat(round(sum(index_length)/(1024*1024),2),"M") "Size of Indexes", concat(round(sum(data_length+index_length)/(1024*1024),2),"M") "Total Size", concat(round(sum(index_length)/sum(data_length)*(100),2), "%") "% Data in Indexes" FROM information_schema.TABLES GROUP BY engine ORDER BY sum(data_length+index_length) DESC LIMIT 10;'</pre>
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| In /etc/my.cnf, change:<br />
| | OOM Killer kills the process with the highest memory usage to prevent the system from running out of memory. It often triggers due to memory load. |
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| <code>innodb_buffer_pool_size</code> - set this to the value from the Total column, innodb row. (Note: if server has lots of RAM, and lots of data, set the innodb_buffer_pool_size = 1G, then set innodb_buffer_pool_instances = 4 (or smaller, or larger, depending on RAM))
| | === Prevent OOM Killer from killing MySQL === |
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| <code>key_buffer_size</code> - set this to the value from the Index column, myisam row. | | You can create a cron job to keep the PID for MySQL updated in the OOM Killer exclusion list: |
| | <code>*/1 * * * * root pgrep -f "/usr/bin/mysql" | while read PID; do echo -1000 > /proc/$PID/oom_score_adj; done</code> |
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| | == References == |
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| === MySQL Error log ===
| | <ul> |
| | | <li>[https://backdrift.org/oom-killer-how-to-create-oom-exclusions-in-linux Backdrift.org - OOM Killer exclusions]</li> |
| To check the MySQL error log, run:<br />
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| <code>mysql -e "show variables like '%log_error%';"</code> | |
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| This will show the location of the MySQL error log, which you can then grep, tail, etc. (You're looking for stuff like innodb errors, disk space issues, connection messages, etc)
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| === View MySQL Variables ===
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| You can view the variables that MySQL is using with:
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| <code>mysql -e "show variables like 'max_connections%';" </code> - This shows the max_connections variable. You can substitute any MySQL variable here.
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| This is helpful for database connection errors, or if a change to /etc/my.cnf isn't 'sticking' (In that case, look for other my.cnf files)
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| === View Currently Running Queries ===
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| <code>mysqladmin process stat</code> - This will show the queries that are running, how many threads, Open tables, slow queries, and a bunch of other helpful stuff. (Note that you can "tail -f" by running: <code>watch mysqladmin process stat</code> )
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MySQL
MySQL Performance Tuning
OOM Killer
OOM Killer kills the process with the highest memory usage to prevent the system from running out of memory. It often triggers due to memory load.
Prevent OOM Killer from killing MySQL
You can create a cron job to keep the PID for MySQL updated in the OOM Killer exclusion list:
*/1 * * * * root pgrep -f "/usr/bin/mysql" | while read PID; do echo -1000 > /proc/$PID/oom_score_adj; done
References