512 MB 記憶體 VPS，安裝 Nginx + PHP-FPM 後剩餘約 150 MB。MySQL 5.6 預設配置啟動即佔用 ~400 MB，導致 OOM Killer 強制終止進程。需精簡配置釋放記憶體。
performance_schema_max_table_instances = 200 table_definition_cache = 200 table_open_cache = 128
這三個參數直接控制 Performance Schema 與表緩存的記憶體上限，預設值過大是 5.6 版本在小記憶體機器上的首殺因素。
[client] port = 3306 socket = /tmp/mysql.sock [mysqld] port = 3306 socket = /tmp/mysql.sock basedir = /usr/local/mysql datadir = /data/mysql pid-file = /data/mysql/mysql.pid user = mysql bind-address = 0.0.0.0 server-id = 1 skip-name-resolve # skip-networking back_log = 600 max_connections = 1000 max_connect_errors = 6000 open_files_limit = 65535 # === 關鍵精簡參數 === table_open_cache = 128 performance_schema = 0 # 完全關閉 P_S，省 ~50-80 MB performance_schema_max_table_instances = 200 table_definition_cache = 200 max_allowed_packet = 4M binlog_cache_size = 1M max_heap_table_size = 8M tmp_table_size = 16M read_buffer_size = 2M read_rnd_buffer_size = 8M sort_buffer_size = 8M join_buffer_size = 8M thread_cache_size = 8 query_cache_size = 8M query_cache_limit = 2M key_buffer_size = 4M ft_min_word_len = 4 transaction_isolation = REPEATABLE-READ log_bin = mysql-bin binlog_format = mixed expire_logs_days = 30 log_error = /data/mysql/mysql-error.log slow_query_log = 1 long_query_time = 1 slow_query_log_file = /data/mysql/mysql-slow.log explicit_defaults_for_timestamp = true skip-external-locking default-storage-engine = InnoDB innodb_file_per_table = 1 innodb_open_files = 500 # === InnoDB 核心記憶體 === innodb_buffer_pool_size = 64M # 物理記憶體 10-15%，512 MB 機器建議 64-96M innodb_write_io_threads = 4 innodb_read_io_threads = 4 innodb_thread_concurrency = 0 innodb_purge_threads = 1 innodb_flush_log_at_trx_commit = 2 # 性能優先，允許 1 秒丟失 innodb_log_buffer_size = 2M innodb_log_file_size = 32M innodb_log_files_in_group = 3 innodb_max_dirty_pages_pct = 90 innodb_lock_wait_timeout = 120 bulk_insert_buffer_size = 8M myisam_sort_buffer_size = 8M myisam_max_sort_file_size = 10G myisam_repair_threads = 1 interactive_timeout = 28800 wait_timeout = 28800 [mysqldump] quick max_allowed_packet = 16M [myisamchk] key_buffer_size = 8M sort_buffer_size = 8M read_buffer = 4M write_buffer = 4M
| 參數 | 作用 | 調整建議 |
|---|---|---|
| performance_schema | 啟用效能監控框架 | 小記憶體建議 0 關閉 |
| table_open_cache | 表緩存數量 | 併發連接數 × 每連接表數，小機器 128-256 |
| innodb_buffer_pool_size | InnoDB 數據+索引緩存 | 獨佔 DB 服務器可設 60-80% 物理記憶體；共用機器設 10-15% |
| innodb_flush_log_at_trx_commit | 事務提交刷盤策略 | 2：每秒刷盤，效能大增，極端崩潰丟 1 秒 |
| query_cache_size | 查詢緩存 | 高併發寫入場景建議關閉（0），讀多寫少可保留 8-16M |
# 啟動後觀察 RSS ps aux | grep mysqld # 預期：RES ~80-120 MB，不再觸發 OOM
小記憶體 VPS 跑 MySQL 5.6 核心策略：關閉 Performance Schema、縮減表緩存、壓縮 Buffer Pool、放寬刷盤策略。上線前務必做壓測，確認無 Table cache full、Out of memory 錯誤。
