Allow parallel access to data files.
------------------------------------
Key: DERBY-801
URL: http://issues.apache.org/jira/browse/DERBY-801
Project: Derby
Type: Improvement
Components: Performance, Store
Versions: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.1.1.1, 10.1.1.2, 10.1.2.0,
10.1.2.1
Environment: Any
Reporter: Øystein Grøvlen
Derby currently serializes accesses to a data file. For example, the
implementation of RAFContainer.readPage is as follows:
synchronized (this) { // 'this' is a FileContainer, i.e. a file object
fileData.seek(pageOffset); // fileData is a RandomAccessFile
fileData.readFully(pageData, 0, pageSize);
}
I have experiemented with a patch where I have introduced several file
descriptors (RandomAccessFile objects) per RAFContainer. These are
used for reading. The principle is that when all readers are busy, a
readPage request will create a new reader. (There is a maximum number
of readers.) With this patch, throughput was improved by 50% on
linux. For more discussion on this, see
http://www.nabble.com/Derby-I-O-issues-during-checkpointing-t473523.html
The challenge with the suggested approach is to make a mechanism to
limit the number of open file descpriptors. Mike Matrigali has
suggested to use the existing CacheManager infrastructure for this
purpose. For a discussion on that, see:
http://www.nabble.com/new-uses-for-basic-services-cache---looking-for-advice-t756863.html
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://issues.apache.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see:
http://www.atlassian.com/software/jira
