Bug #56646 Add option to disable readahead in innodb
Submitted: 8 Sep 2010 13:15 Modified: 20 Dec 2013 15:52
Reporter: Inaam Rana Email Updates:
Status: Closed Impact on me:
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
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:


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:alexander.nozdrin@oracle.com-20101113155825-czmva9kg4n31anmu) (version source revid:alexander.nozdrin@oracle.com-20101113152450-2zzcm50e7i4j35v7) (merge vers: 5.6.1-m4) (pib:21)
[13 Nov 2010 16:41] Bugs System
Pushed into mysql-next-mr (revid:alexander.nozdrin@oracle.com-20101113160336-atmtmfb3mzm4pz4i) (version source revid:vasil.dimov@oracle.com-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."