后台线程
- Master Thread
刷脏页(1.2之后有专门线程负责 PageCleanerThread)、合并插入缓冲(INSERT BUFFER)、回收undo页(1.1之后有专门线程负责 PurgeThread) - IO Thread
AIO
innodb_file_io_threads
innodb_read_io_threads
innodb_write_io_threads - Purge Thread
事物提交后其所有的undolog可能不再需要,使用PurgeThread来回收已经使用并分配的undo页
[mysqld]
innodb_purge_thread=1 - Page Cleaner Thread