innodb_page_cleaners是MySQL中的刷脏线程个数，它的值等于innodb_buffer_pool_instances的值，如果innodb_page_cleaners的值大于innodb_buffer_pool_instances的值，那么自动的将innodb_page_cleaners调整为与innodb_buffer_pool_instances的值相同，其他情况不做调整。

默认值都是1，如下图：

[test]> select @@innodb_page_cleaners;
+------------------------+
| @@innodb_page_cleaners |
+------------------------+
|                      1 |
+------------------------+

[test]> select @@innodb_buffer_pool_instances;
+--------------------------------+
| @@innodb_buffer_pool_instances |
+--------------------------------+
|                              1 |
+--------------------------------+

innodb_page_cleaners是由一个协调线程+一个或多个task线程组成的。如果innodb_page_cleaners=1，那么它本身就是协调线程，又是工作线程。

innodb_buffer_pool_instances的值默认是1。innodb_buffer_pool_instances指的是将innodb buffer pool划分为多少个区域，区域的数量就是innodb_buffer_pool_instances的值。目的是为了便于管理减少锁的粒度，提高并发性。

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