From the document,I see the descriptions about the two status.
These global status variables Innodb_buffer_pool_read_ahead and Innodb_buffer_pool_read_ahead_evicted indicate the number of pages read in as part of read ahead and the number of such pages evicted without ever being accessed respectively.
But when I inspect the two status,I find Innodb_buffer_pool_read_ahead_evicted is big than Innodb_buffer_pool_read_ahead.
show global status like '%ahead%';
+---------------------------------------+-----------+
| Variable_name | Value |
+---------------------------------------+-----------+
| Innodb_buffer_pool_read_ahead | 520841 |
| Innodb_buffer_pool_read_ahead_evicted | 193493770 |
+---------------------------------------+-----------+
These global status variables Innodb_buffer_pool_read_ahead and Innodb_buffer_pool_read_ahead_evicted indicate the number of pages read in as part of read ahead and the number of such pages evicted without ever being accessed respectively.
But when I inspect the two status,I find Innodb_buffer_pool_read_ahead_evicted is big than Innodb_buffer_pool_read_ahead.
show global status like '%ahead%';
+---------------------------------------+-----------+
| Variable_name | Value |
+---------------------------------------+-----------+
| Innodb_buffer_pool_read_ahead | 520841 |
| Innodb_buffer_pool_read_ahead_evicted | 193493770 |
+---------------------------------------+-----------+