充分利用CPU多核的處理能力 innodb_read_io_threads和innodb_write_io_threads

https://book.2cto.com/201402/40300.html

在MySQL5.1.X版本中，innodb_file_io_threads參數默認是4，該參數在Linux系統上是不可更改的，但Windows系統上能夠調整。這個參數的做用是：InnoDB使用後臺線程處理數據頁上讀寫I/O（輸入輸出）請求的數量。

在MySQL5.5.X版本中，或者說是在InnoDB Plugin1.0.4之後，就用兩個新的參數，即innodb_read_io_threads和innodb_write_io_threads，取代了innodb_file_io_threads如此調整後，在Linux平臺上就能夠根據CPU核數來更改相應的參數值了，默認是4。

假如CPU是2顆8核的，那麼能夠設置：
innodb_read_io_threads = 8
innodb_write_io_threads = 8

若是數據庫的讀操做比寫操做多，那麼能夠設置：
innodb_read_io_threads = 10
innodb_write_io_threads = 6

也就是說，你能夠根據狀況加以設置。

注意

這兩個參數不支持動態改變，須要把該參數加入my.cnf裏，修改完後重啓MySQL服務，容許值的範圍是1～64。

調整完成後，你能夠用命令「show engine innodb status\G;」來查看調整結果，以下所示：
show engine innodb status
--------
FILE I/O
--------
I/O thread 0 state: waiting for completed aio requests (insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log thread)
I/O thread 2 state: waiting for completed aio requests (read thread)
I/O thread 3 state: waiting for completed aio requests (read thread)
I/O thread 4 state: waiting for completed aio requests (read thread)
I/O thread 5 state: waiting for completed aio requests (read thread)
I/O thread 6 state: waiting for completed aio requests (write thread)
I/O thread 7 state: waiting for completed aio requests (write thread)
I/O thread 8 state: waiting for completed aio requests (write thread)
I/O thread 9 state: waiting for completed aio requests (write thread)

關於innodb_read_io_threads和innodb_write_io_threads參數的含義，請參見MySQL5.5 手冊：