Bug #71328 Manual does not describe how to monitor InnoDB change buffer usage
Submitted: 9 Jan 2014 14:27 Modified: 26 May 2015 13:05
Reporter: Valeriy Kravchuk Email Updates:
Status: Closed Impact on me:
Category:MySQL Server: Documentation Severity:S3 (Non-critical)
Version:5.1, 5.5, 5.6 OS:Any
Assigned to: Daniel Price CPU Architecture:Any
Tags: change buffering, innodb, innodb_change_buffer_max_size, missing manual

[9 Jan 2014 14:27] Valeriy Kravchuk
Manual describes how change buffer works and what options are there to control it, at http://dev.mysql.com/doc/refman/5.6/en/innodb-performance.html#innodb-performance-change_b.... I see two problems in that section:

1. It does not say anything about new 5.6 option to control memory allocated for the change buffer, http://dev.mysql.com/doc/refman/5.6/en/innodb-parameters.html#sysvar_innodb_change_buffer_...

2. It does not explain how to monitor change buffer usage, for example it's current size. In 5.6 we have several rows in the INFORMATION_SCHEMA.INNODB_METRICS for this:

mysql> select name, `count` from information_schema.innodb_metrics where name like 'ibuf%';
| name                            | count  |
| ibuf_merges_insert              |      0 |
| ibuf_merges_delete_mark         | 519100 |
| ibuf_merges_delete              |      0 |
| ibuf_merges_discard_insert      |      0 |
| ibuf_merges_discard_delete_mark |      0 |
| ibuf_merges_discard_delete      |      0 |
| ibuf_merges                     |   3613 |
| ibuf_size                       |      1 |
8 rows in set (0.01 sec)

(maybe more). In all versions we have this section in INNODB STATUS:

Ibuf: size 1, free list len 174, seg size 176, 3613 merges
merged operations:
 insert 0, delete mark 519100, delete 0
discarded operations:
 insert 0, delete mark 0, delete 0

So, manual should explain these values and their use to monitor and set proper size of change buffer for the load.

If there are some other ways to control/monitor usage of change buffer, describe them.

How to repeat:
Try to find out, based on the manual, how large your InnoDB change buffer is and how it is used (if at all).

Suggested fix:
Describe all know ways to monitor and control InnoDB change buffer usage in all versions.
[10 Jan 2014 4:58] MySQL Verification Team
Hello Valeriy,

Thank you for the bug report.

[26 May 2015 13:05] Daniel Price
Posted by developer:
Information about change buffer monitoring has been added to the following pages:


Information about configuring change buffer maximum size has been added here:


The latest content should appear on-line within 24 hours.

Thank you for the bug report.