MySQL 8.0 的 innodb_dedicated_server

Percona 介紹了 MySQL 8.0 將會推出的 innodb_dedicated_server 參數:「New MySQL 8.0 innodb_dedicated_server Variable Optimizes InnoDB from the Get-Go」,Oracle 官方的文件在「15.6.13 Enabling Automatic Configuration for a Dedicated MySQL Server」這邊可以翻到。

這是針對整台機器完全給 MySQL 用的情況所設計的參數。在這種情況下,可以透過 RAM 的大小以及一些簡單的公式,得到還算堪用的系統參數...

依照說明,可以看到系統會依照記憶體的大小自動計算出 innodb_buffer_pool_sizeinnodb_log_file_size 這兩個參數,並且把 innodb_flush_method 設為 O_DIRECT_NO_FSYNC (如果所在平台有支援這個值)。

不過看了一下公式,依照經驗可以設的更積極一點... 像是 Percona 文章裡提到的,當記憶體夠大時,其實可以考慮從 80% 開始調整大小 (innodb_buffer_pool_size):

For InnoDB buffer pool size (based on this article), consider allocating 80% of physical RAM for starters. You can increase it to as large as needed and possible, as long as the system doesn’t swap on the production workload.

innodb_log_file_size 則應該要分析寫入的 pattern 而不是直接看 RAM 大小。有些機器雖然很大台但幾乎沒有寫入的量,照著公式的值就偏大很多:

For InnoDB log file size, it should be able to handle one hour of writes to allow InnoDB to optimize writing the redo log to disk. You can calculate an estimate by following the steps here, which samples one minute worth of writes to the redo log. You could also get a better estimate from hourly log file usage with Percona Monitoring and Management (PMM) graphs.

不過基本上 tune 出來的值還算堪用,對於剛入手的人頗有幫助。

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