MySQL Optimization - MySQL's maximum memory usage is dangerously high

johncarlopogix

• October 31, 2021 13:21

I have a cPanel/CentOS 7.9 (cloudlinux) VPS with 4 GB RAM. I ran the MySQLTuner script, and followed the recommendations that they gave, but it's still recommending increases, while telling me that MySQL's maximum memory usage is dangerously high. My current config in my my.cnf file is: [mysql] port = 3306 socket = /var/lib/mysql/mysql.sock [mysqld] performance_schema = on basedir = /usr bind_address = 127.0.0.1 datadir = /var/lib/mysql max_allowed_packet = 256M max_connect_errors = 1000000 pid_file = /var/lib/mysql/mysql.pid port = 3306 skip_external_locking socket = /var/lib/mysql/mysql.sock tmpdir = /tmp user = mysql default_storage_engine = InnoDB innodb_buffer_pool_instances = 4 innodb_buffer_pool_size = 4G innodb_file_per_table = 1 innodb_flush_log_at_trx_commit = 0 innodb_flush_method = O_DIRECT innodb_log_buffer_size = 16M innodb_log_file_size = 1G innodb_stats_on_metadata = 0 innodb_read_io_threads = 64 innodb_write_io_threads = 64 query_cache_limit = 2M query_cache_size = 0 query_cache_type = 0 key_buffer_size = 32M low_priority_updates = 1 concurrent_insert = 2 max_connections = 100 back_log = 512 thread_cache_size = 100 thread_stack = 192K interactive_timeout = 180 wait_timeout = 180 innodb_sort_buffer_size = 512M join_buffer_size = 4M read_buffer_size = 3M read_rnd_buffer_size = 4M sort_buffer_size = 4M max_heap_table_size = 128M tmp_table_size = 128M ft_min_word_len = 3 log_error = /var/lib/mysql/mysql_error.log log_queries_not_using_indexes = 1 long_query_time = 5 slow_query_log = 0 slow_query_log_file = /var/lib/mysql/mysql_slow.log [mysqldump] quick quote_names max_allowed_packet = 512M
I restarted MySQL a short while ago to apply my most recent changes. When I run the script, this is what I get: >> MySQLTuner 1.8.5 - Major Hayden >> Bug reports, feature requests, and downloads at http://mysqltuner.pl/ >> Run with '--help' for additional options and output filtering [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 10.3.31-MariaDB-cll-lve [OK] Operating on 64-bit architecture -------- Log file Recommendations ------------------------------------------------------------------ [OK] Log file /var/lib/mysql/mysql_error.log exists [--] Log file: /var/lib/mysql/mysql_error.log(151K) [OK] Log file /var/lib/mysql/mysql_error.log is not empty [OK] Log file /var/lib/mysql/mysql_error.log is smaller than 32 Mb [OK] Log file /var/lib/mysql/mysql_error.log is readable. [!!] /var/lib/mysql/mysql_error.log contains 911 warning(s). [!!] /var/lib/mysql/mysql_error.log contains 5 error(s). [--] 23 start(s) detected in /var/lib/mysql/mysql_error.log [--] 1) 2021-11-01 2:16:53 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 2) 2021-11-01 1:55:23 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 3) 2021-11-01 1:26:25 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 4) 2021-10-30 22:14:42 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 5) 2021-10-30 21:42:56 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 6) 2021-10-30 13:18:21 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 7) 2021-10-30 13:09:44 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 8) 2021-10-30 10:37:44 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 9) 2021-10-29 0:44:51 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 10) 2021-10-29 0:25:05 0 [Note] /usr/sbin/mysqld: ready for connections. [--] 22 shutdown(s) detected in /var/lib/mysql/mysql_error.log [--] 1) 2021-11-01 2:16:49 0 [Note] /usr/sbin/mysqld: Shutdown complete [--] 2) 2021-11-01 1:55:19 0 [Note] /usr/sbin/mysqld: Shutdown complete [--] 3) 2021-11-01 1:25:51 0 [Note] /usr/sbin/mysqld: Shutdown complete [--] 4) 2021-10-30 22:14:07 0 [Note] /usr/sbin/mysqld: Shutdown complete [--] 5) 2021-10-30 21:42:52 0 [Note] /usr/sbin/mysqld: Shutdown complete [--] 6) 2021-10-30 13:18:17 0 [Note] /usr/sbin/mysqld: Shutdown complete [--] 7) 2021-10-30 13:09:40 0 [Note] /usr/sbin/mysqld: Shutdown complete [--] 8) 2021-10-30 10:37:08 0 [Note] /usr/sbin/mysqld: Shutdown complete [--] 9) 2021-10-29 0:44:47 0 [Note] /usr/sbin/mysqld: Shutdown complete [--] 10) 2021-10-29 0:25:01 0 [Note] /usr/sbin/mysqld: Shutdown complete -------- Storage Engine Statistics ----------------------------------------------------------------- [--] Status: +Aria +CSV +InnoDB +MEMORY +MRG_MyISAM +MyISAM +PERFORMANCE_SCHEMA +SEQUENCE [--] Data in MyISAM tables: 28.7K (Tables: 10) [--] Data in InnoDB tables: 16.2M (Tables: 90) [OK] Total fragmented tables: 0 -------- Analysis Performance Metrics -------------------------------------------------------------- [--] innodb_stats_on_metadata: OFF [OK] No stat updates during querying INFORMATION_SCHEMA. -------- Security Recommendations ------------------------------------------------------------------ [OK] There are no anonymous accounts for any database users [OK] All database users have passwords assigned [!!] There is no basic password file list! -------- CVE Security Recommendations -------------------------------------------------------------- [--] Skipped due to --cvefile option undefined -------- Performance Metrics ----------------------------------------------------------------------- [--] Up for: 53s (52 q [0.981 qps], 25 conn, TX: 66K, RX: 4K) [--] Reads / Writes: 100% / 0% [--] Binary logging is disabled [--] Physical Memory : 3.6G [--] Max MySQL memory : 30.9G [--] Other process memory: 0B [--] Total buffers: 4.3G global + 271.2M per thread (100 max threads) [--] P_S Max memory usage: 95M [--] Galera GCache Max memory usage: 0B [!!] Maximum reached memory usage: 4.9G (136.42% of installed RAM) [!!] Maximum possible memory usage: 30.9G (856.04% of installed RAM) [!!] Overall possible memory usage with other process exceeded memory [OK] Slow queries: 0% (0/52) [OK] Highest usage of available connections: 2% (2/100) [!!] Aborted connections: 4.00% (1/25) [!!] name resolution is active : a reverse name resolution is made for each new connection and can reduce performance [OK] Query cache is disabled by default due to mutex contention on multiprocessor machines. [OK] No Sort requiring temporary tables [OK] No joins without indexes [OK] Temporary tables created on disk: 0% (0 on disk / 4 total) [OK] Thread cache hit rate: 92% (2 created / 25 connections) [!!] Table cache hit rate: 5% (1 hits / 19 requests) [OK] table_definition_cache(400) is upper than number of tables(367) [OK] Open file limit used: 0% (23/32K) [OK] Table locks acquired immediately: 100% (11 immediate / 11 locks) -------- Performance schema ------------------------------------------------------------------------ [--] Memory used by P_S: 95.7M [--] Sys schema is installed. -------- ThreadPool Metrics ------------------------------------------------------------------------ [--] ThreadPool stat is enabled. [--] Thread Pool Size: 4 thread(s). [--] Using default value is good enough for your version (10.3.31-MariaDB-cll-lve) -------- MyISAM Metrics ---------------------------------------------------------------------------- [!!] Key buffer used: 18.3% (6M used / 33M cache) [OK] Key buffer size / total MyISAM indexes: 32.0M/91.0K [!!] Read Key buffer hit rate: 50.0% (8 cached / 4 reads) -------- InnoDB Metrics ---------------------------------------------------------------------------- [--] InnoDB is enabled. [--] InnoDB Thread Concurrency: 0 [OK] InnoDB File per table is activated [OK] InnoDB buffer pool / data size: 4.0G/16.2M [!!] Ratio InnoDB log file size / InnoDB Buffer pool size (50 %): 1.0G * 2/4.0G should be equal to 25% [OK] InnoDB buffer pool instances: 4 [--] Number of InnoDB Buffer Pool Chunk : 32 for 4 Buffer Pool Instance(s) [OK] Innodb_buffer_pool_size aligned with Innodb_buffer_pool_chunk_size & Innodb_buffer_pool_instances [!!] InnoDB Read buffer efficiency: 39.35% (929 hits/ 2361 total) [!!] InnoDB Write Log efficiency: 0% (1 hits/ 0 total) [OK] InnoDB log waits: 0.00% (0 waits / 1 writes) -------- Aria Metrics ------------------------------------------------------------------------------ [--] Aria Storage Engine is enabled. [OK] Aria pagecache size / total Aria indexes: 128.0M/0B -------- TokuDB Metrics ---------------------------------------------------------------------------- [--] TokuDB is disabled. -------- XtraDB Metrics ---------------------------------------------------------------------------- [--] XtraDB is disabled. -------- Galera Metrics ---------------------------------------------------------------------------- [--] Galera is disabled. -------- Replication Metrics ----------------------------------------------------------------------- [--] Galera Synchronous replication: NO [--] No replication slave(s) for this server. [--] Binlog format: MIXED [--] XA support enabled: ON [--] Semi synchronous replication Master: OFF [--] Semi synchronous replication Slave: OFF [--] This is a standalone server -------- Recommendations --------------------------------------------------------------------------- General recommendations: Check warning line(s) in /var/lib/mysql/mysql_error.log file Check error line(s) in /var/lib/mysql/mysql_error.log file MySQL was started within the last 24 hours - recommendations may be inaccurate Reduce your overall MySQL memory footprint for system stability Dedicate this server to your database for highest performance. Reduce or eliminate unclosed connections and network issues Configure your accounts with ip or subnets only, then update your configuration with skip-name-resolve=1 Increase table_open_cache gradually to avoid file descriptor limits Read this before increasing table_open_cache over 64: https://bit.ly/2Fulv7r Read this before increasing for MariaDB https://mariadb.com/kb/en/library/optimizing-table_open_cache/ This is MyISAM only table_cache scalability problem, InnoDB not affected. See more details here: https://bugs.mysql.com/bug.php?id=49177 This bug already fixed in MySQL 5.7.9 and newer MySQL versions. Beware that open_files_limit (32135) variable should be greater than table_open_cache (2000) Before changing innodb_log_file_size and/or innodb_log_files_in_group read this: https://bit.ly/2TcGgtU Variables to adjust: *** MySQL's maximum memory usage is dangerously high *** *** Add RAM before increasing MySQL buffer variables *** table_open_cache (> 2000) innodb_log_file_size should be (=512M) if possible, so InnoDB total log files size equals to 25% of buffer pool size.
Does anyone have any recommendations with what to do now? Thanks a lot!

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  cPanelAnthony

  • October 31, 2021 19:15

  Hello! It's hard to say for sure how you should optimize MySQL. 4GB of RAM is not a whole lot; it could depend on how many databases you have, how active each database is, what kind of queries or work is being done with each database, how large the databases are, etc... It could simply be that your server doesn't have enough RAM for the amount of work the databases are performing. With that being said, I am not a systems administrator and cannot make any promises in regards to what you need to do in order to get MySQL running smoothly. Perhaps some of the other users here will be able to offer some guidance.

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  RoseHosting

  • November 01, 2021 00:25

  You can lower your innodb_buffer_pool_size value, because according to your MySQL Tuner script result, your InnoDB data size is only around 16MB.

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  devil2580

  • November 01, 2021 08:14

  Hi Hope you are doing well Please check the bellow link for this problem : Help with MySQL's maximum memory usage which is dangerously high. Feel free to contact us more support.

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