Bug #56646 Add option to disable readahead in innodb

• Submitted: 8 Sep 2010 13:15
• Modified: 20 Dec 2013 15:52
• Reporter: Inaam Rana
• Status: Closed
• Category: MySQL Server: InnoDB storage engine
• Severity: S3 (Non-critical)
• Version: 5.6
• OS: Any
• Assigned to: Assigned Account
• CPU Architecture: Any

[8 Sep 2010 13:15] Inaam Rana

Description:
Currently we have innodb_read_ahead_threshold with valid values from 0 - 64. As the value is increased from 0 to 64 the access pattern condition becomes more and more strict progressively.
There may be cases where readahead needs to be disabled completely (particularly where we are using SSD).

How to repeat:
see above.

Suggested fix:
Mark 0 as a special value for readahead which completely disables the functionality.

[9 Sep 2010 12:24] Bugs System

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/117856

3238 Inaam Rana	2010-09-09
      bug#56646 Add option to disable readahead in innodb
      
      With this fix the value '0' will mean that no readahead will take place.

[13 Nov 2010 16:15] Bugs System

Pushed into mysql-trunk 5.6.99-m5 (revid:[e-mail]-20101113155825-czmva9kg4n31anmu) (version source revid:[e-mail]-20101113152450-2zzcm50e7i4j35v7) (merge vers: 5.6.1-m4) (pib:21)

[13 Nov 2010 16:41] Bugs System

Pushed into mysql-next-mr (revid:[e-mail]-20101113160336-atmtmfb3mzm4pz4i) (version source revid:[e-mail]-20100629074804-359l9m9gniauxr94) (pib:21)

[20 Dec 2013 15:52] Daniel Price

Noted in 5.6.1 changelog:

"Setting "innodb_read_ahead_threshold" to "0" disables read-ahead. Prior
to 5.6.1, a value of "0" would trigger a read-ahead upon reading the
boundary page of a 64 page extent."