how to fix mysql high memory usage?


I used mysqltuner to check the problem related to frequent crashes of my database. I received this warning

*** MySQL’s maximum memory usage is dangerously high ***

Here’s the result of mysqltuner:


`>> MySQLTuner 1.4.0 - Major Hayden

Bug reports, feature requests, and downloads at Run with ‘–help’ for additional options and output filtering Please enter your MySQL administrative login: Please enter your MySQL administrative password: [OK] Currently running supported MySQL version 5.5.42-log [OK] Operating on 64-bit architecture

-------- Storage Engine Statistics ------------------------------------------- [–] Status: +ARCHIVE +BLACKHOLE +CSV -FEDERATED +InnoDB +MRG_MYISAM [–] Data in MyISAM tables: 51M (Tables: 3) [–] Data in InnoDB tables: 653M (Tables: 233) [–] Data in PERFORMANCE_SCHEMA tables: 0B (Tables: 17) [–] Data in MEMORY tables: 372K (Tables: 5) [!!] Total fragmented tables: 34

-------- Security Recommendations ------------------------------------------- [OK] All database users have passwords assigned

-------- Performance Metrics ------------------------------------------------- [–] Up for: 34m 50s (46K q [22.025 qps], 3K conn, TX: 3B, RX: 18M) [–] Reads / Writes: 86% / 14% [–] Total buffers: 672.0M global + 2.8M per thread (500 max threads) [!!] Maximum possible memory usage: 2.0G (205% of installed RAM) [OK] Slow queries: 4% (1K/46K) [OK] Highest usage of available connections: 1% (6/500) [OK] Key buffer size / total MyISAM indexes: 32.0M/51.3M [OK] Key buffer hit rate: 98.8% (55K cached / 675 reads) [!!] Query cache is disabled [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 1K sorts) [!!] Joins performed without indexes: 8 [OK] Temporary tables created on disk: 22% (103 on disk / 455 total) [OK] Thread cache hit rate: 99% (6 created / 3K connections) [OK] Table cache hit rate: 33% (142 open / 420 opened) [OK] Open file limit used: 0% (56/65K) [OK] Table locks acquired immediately: 99% (70K immediate / 70K locks) [!!] InnoDB buffer pool / data size: 592.0M/653.4M [OK] InnoDB log waits: 0 -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance MySQL started within last 24 hours - recommendations may be inaccurate Reduce your overall MySQL memory footprint for system stability Adjust your join queries to always utilize indexes Variables to adjust: *** MySQL’s maximum memory usage is dangerously high *** *** Add RAM before increasing MySQL buffer variables *** query_cache_size (>= 8M) join_buffer_size (> 128.0K, or always use indexes with joins) innodb_buffer_pool_size (>= 653M)

And here's my my.cnf config.

Generated by Percona Configuration Wizard ( version REL5-20120208

Configuration name server generated for …



port = 3306 socket = /var/lib/mysql/mysql.sock



user = mysql default-storage-engine = InnoDB socket = /var/lib/mysql/mysql.sock pid-file = /var/lib/mysql/ performance_schema = off


key-buffer-size = 10M myisam-recover = FORCE,BACKUP


max-allowed-packet = 10M max-connect-errors = 1000000 skip-name-resolve sql-mode = STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_AUTO_VALUE_ON_ZERO,NO_ENGINE_SUBSTITUTION,NO_ZERO_DATE,NO_ZERO_IN_DATE,ONLY_FULL_GROUP_BY sysdate-is-now = 1 innodb = FORCE


datadir = /var/lib/mysql/


log-bin = /var/lib/mysql/mysql-bin expire-logs-days = 7 sync-binlog = 1


tmp-table-size = 20M max-heap-table-size = 32M query-cache-type = 1 query-cache-size = 32M max-connections = 50 thread-cache-size = 50 open-files-limit = 1500 table-definition-cache = 4096 table-open-cache = 4096


innodb-flush-method = O_DIRECT innodb-log-files-in-group = 2 innodb-log-file-size = 80M innodb-flush-log-at-trx-commit = 1 innodb-file-per-table = 1 innodb-buffer-pool-size = 700M


log-error = /var/lib/mysql/mysql-error.log log-queries-not-using-indexes = 1 slow-query-log = 1 slow-query-log-file = /var/lib/mysql/mysql-slow.log

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