High CPU usage from mysql process

cyrilarnaud

• April 13, 2022 06:19

Hi, I'm trying to understand what is not working in my configuration. I have high CPU usage and the site becomes really sluggish when I have a lot of connections. [root@server ~]# wget mysqltuner.pl [root@server ~]# ./ >> Run with '--help' for additional options and output filtering [--] Skipped version check for MySQLTuner script [!!] Your MySQL version 10.2.43-MariaDB-log is EOL software! Upgrade soon! [OK] Operating on 64-bit architecture -------- Log file Recommendations ------------------------------------------------------------------ [OK] Log file /var/log/mysqld.log exists [--] Log file: /var/log/mysqld.log(1M) [OK] Log file /var/log/mysqld.log is not empty [OK] Log file /var/log/mysqld.log is smaller than 32 Mb [OK] Log file /var/log/mysqld.log is readable. [!!] /var/log/mysqld.log contains 7269 warning(s). [!!] /var/log/mysqld.log contains 2370 error(s). [--] 65 start(s) detected in /var/log/mysqld.log [--] 1) 2022-04-11 15:13:19 140028901791936 [Note] /usr/sbin/mysqld: ready for connections. [--] 2) 2022-03-29 2:44:09 140256877758656 [Note] /usr/sbin/mysqld: ready for connections. [--] 3) 2022-03-22 2:42:21 140486199806144 [Note] /usr/sbin/mysqld: ready for connections. [--] 4) 2022-02-14 2:42:44 139938060060864 [Note] /usr/sbin/mysqld: ready for connections. [--] 5) 2022-02-14 2:42:41 139960106510528 [Note] /usr/sbin/mysqld: ready for connections. [--] 6) 2022-02-09 2:45:31 140350442416320 [Note] /usr/sbin/mysqld: ready for connections. [--] 7) 2022-02-09 2:45:28 139988696365248 [Note] /usr/sbin/mysqld: ready for connections. [--] 8) 2022-02-03 10:44:37 140367947258048 [Note] /usr/sbin/mysqld: ready for connections. [--] 9) 2022-01-19 2:42:35 139626621569216 [Note] /usr/sbin/mysqld: ready for connections. [--] 10) 2022-01-15 2:42:36 140408995231936 [Note] /usr/sbin/mysqld: ready for connections. [--] 46 shutdown(s) detected in /var/log/mysqld.log [--] 1) 2022-04-11 15:12:31 140255785293568 [Note] /usr/sbin/mysqld: Shutdown complete [--] 2) 2022-03-29 2:44:09 140485092288256 [Note] /usr/sbin/mysqld: Shutdown complete [--] 3) 2022-03-22 2:42:20 139937820497664 [Note] /usr/sbin/mysqld: Shutdown complete [--] 4) 2022-02-14 2:42:44 139959094945536 [Note] /usr/sbin/mysqld: Shutdown complete [--] 5) 2022-02-14 2:42:40 140349468514048 [Note] /usr/sbin/mysqld: Shutdown complete [--] 6) 2022-02-09 2:45:31 139987684747008 [Note] /usr/sbin/mysqld: Shutdown complete [--] 7) 2022-02-09 2:45:27 140367091803904 [Note] /usr/sbin/mysqld: Shutdown complete [--] 8) 2022-02-03 10:44:04 139625362011904 [Note] /usr/sbin/mysqld: Shutdown complete [--] 9) 2022-01-19 2:42:34 140408137303808 [Note] /usr/sbin/mysqld: Shutdown complete [--] 10) 2022-01-15 2:42:36 140653404616448 [Note] /usr/sbin/mysqld: Shutdown complete -------- Storage Engine Statistics ----------------------------------------------------------------- [--] Status: +Aria +CSV +InnoDB +MEMORY +MRG_MyISAM +MyISAM +PERFORMANCE_SCHEMA +SEQUENCE [--] Data in InnoDB tables: 3.9G (Tables: 718) [OK] Total fragmented tables: 0 -------- Analysis Performance Metrics -------------------------------------------------------------- [--] innodb_stats_on_metadata: OFF [OK] No stat updates during querying INFORMATION_SCHEMA. -------- Views Metrics ----------------------------------------------------------------------------- -------- Triggers Metrics -------------------------------------------------------------------------- -------- Routines Metrics -------------------------------------------------------------------------- -------- 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: 1d 19h 9m 26s (15M q [100.575 qps], 99K conn, TX: 140G, RX: 3G) [--] Reads / Writes: 94% / 6% [--] Binary logging is disabled [--] Physical Memory : 7.6G [--] Max MySQL memory : 38.9G [--] Other process memory: 0B [--] Total buffers: 672.0M global + 258.9M per thread (151 max threads) [--] P_S Max memory usage: 93M [--] Galera GCache Max memory usage: 0B [OK] Maximum reached memory usage: 5.8G (76.00% of installed RAM) [!!] Maximum possible memory usage: 38.9G (509.71% of installed RAM) [!!] Overall possible memory usage with other process exceeded memory [OK] Slow queries: 0% (2K/15M) [OK] Highest usage of available connections: 13% (20/151) [OK] Aborted connections: 0.05% (48/99272) [!!] CPanel and Flex system skip-name-resolve should be on [OK] Query cache is disabled by default due to mutex contention on multiprocessor machines. [OK] Sorts requiring temporary tables: 0% (143 temp sorts / 2M sorts) [!!] Joins performed without indexes: 28007 [!!] Temporary tables created on disk: 89% (1M on disk / 2M total) [OK] Thread cache hit rate: 99% (20 created / 99K connections) [OK] Table cache hit rate: 61% (985 hits / 1K requests) [OK] table_definition_cache(2097152) is upper than number of tables(984) [OK] Open file limit used: 0% (39/40K) [OK] Table locks acquired immediately: 100% (671 immediate / 671 locks) -------- Performance schema ------------------------------------------------------------------------ [--] Performance_schema is activated. [--] Memory used by P_S: 93.6M [--] Sys schema is installed. -------- ThreadPool Metrics ------------------------------------------------------------------------ [--] ThreadPool stat is disabled. -------- MyISAM Metrics ---------------------------------------------------------------------------- [!!] Key buffer used: 18.3% (23.4M used / 128.0M cache) [OK] Key buffer size / total MyISAM indexes: 128.0M/137.0K [OK] Read Key buffer hit rate: 99.7% (29K cached / 93 reads) -------- InnoDB Metrics ---------------------------------------------------------------------------- [--] InnoDB is enabled. [--] InnoDB Thread Concurrency: 0 [OK] InnoDB File per table is activated [!!] InnoDB buffer pool / data size: 384.0M/3.9G [!!] Ratio InnoDB log file size / InnoDB Buffer pool size (7.29166666666667 %): 14.0M * 2/384.0M should be equal to 25% [OK] InnoDB buffer pool instances: 1 [--] Number of InnoDB Buffer Pool Chunk : 3 for 1 Buffer Pool Instance(s) [OK] Innodb_buffer_pool_size aligned with Innodb_buffer_pool_chunk_size & Innodb_buffer_pool_instances [OK] InnoDB Read buffer efficiency: 99.73% (12234434681 hits/ 12268060005 total) [!!] InnoDB Write Log efficiency: 85.47% (4526473 hits/ 5296273 total) [OK] InnoDB log waits: 0.00% (0 waits / 769800 writes) -------- Aria Metrics ------------------------------------------------------------------------------ [--] Aria Storage Engine is enabled. [OK] Aria pagecache size / total Aria indexes: 128.0M/0B [OK] Aria pagecache hit rate: 98.8% (127M cached / 1M reads) -------- 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: Not Activated [--] Semi synchronous replication Slave: Not Activated [--] This is a standalone server -------- Recommendations --------------------------------------------------------------------------- General recommendations: You are using n unsupported version for production environments Upgrade as soon as possible to a supported version ! Check warning line(s) in /var/log/mysqld.log file Check error line(s) in /var/log/mysqld.log file Reduce your overall MySQL memory footprint for system stability Dedicate this server to your database for highest performance. name resolution is enabled due to cPanel doesn't support this disabled. We will suggest raising the 'join_buffer_size' until JOINs not using indexes are found. See Variables to adjust: *** MySQL's maximum memory usage is dangerously high *** *** Add RAM before increasing MySQL buffer variables *** skip-name-resolve=0 join_buffer_size (> 256.0K, or always use indexes with JOINs) tmp_table_size (> 16M) max_heap_table_size (> 16M) key_buffer_size (~ 24M) innodb_buffer_pool_size (>= 3.9G) if possible. innodb_log_file_size should be (=48M) if possible, so InnoDB total log files size equals to 25% of buffer pool size.
Here is my /etc/my.cnf [root@server ~]# cat /etc/my.cnf # For advice on how to change settings please see # http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html [mysqld] performance-schema=0 # # Remove leading # and set to the amount of RAM for the most important data # cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%. # innodb_buffer_pool_size = 128M # # Remove leading # to turn on a very important data integrity option: logging # changes to the binary log between backups. # log_bin # # Remove leading # to set options mainly useful for reporting servers. # The server defaults are faster for transactions and fast SELECTs. # Adjust sizes as needed, experiment to find the optimal values. # join_buffer_size = 128M # sort_buffer_size = 2M # read_rnd_buffer_size = 2M datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock # Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links=0 log-error=/var/log/mysqld.log # pid-file=/var/run/mysqld/mysqld.pid innodb_buffer_pool_size=122683392 max_allowed_packet=268435456 open_files_limit=40000 innodb_file_per_table=1 query_cache_size=0 query_cache_type=0 query_cache_limit=1M tmp_table_size=16M max_heap_table_size=16M performance_schema=ON innodb_buffer_pool_size=260M innodb_log_file_size=14M table_definition_cache=-1 slow_query_log = 1 slow-query_log_file = /var/log/mysql-slow.log long_query_time = 2
I would like to resolve the "MySQL's maximum memory usage is dangerously high" and improve the performance. I have 8G of RAM on this server and I don't seem to have memory problems, only CPU ones (I have 6 CPUs on this VM). Any help would be greatly appreciated. Thanks

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  cPRex Jurassic Moderator

  • April 13, 2022 14:46

  Hey there! During one of the times you see the slowness with MySQL, run the following command: mysqladmin proc status
  and that will show you in real-time what is happening with the server. Once we have that data we may be able to make a recommendation.

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  cyrilarnaud

  • April 14, 2022 16:03

  Of course since I posted this there are less problems the point that concerns me the most is the message "MySQL's maximum memory usage is dangerously high" in the mysqltuner.pl. I would like to understand how it's that high, and how I can optimize the usage of the memory and CPU I have available.

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  cyrilarnaud

  • April 14, 2022 16:14

  I don't understand why, I can't paste here the result of mysqladmin

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  cPRex Jurassic Moderator

  • April 14, 2022 16:27

  MySQL itself doesn't have a hard memory limit value. It takes several of the configuration options together, such as caching and open files, and that determines how much memory in total it can use. There are more details from the MySQL team on how that is calculated here:

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