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Posted to derby-dev@db.apache.org by "Knut Anders Hatlen (JIRA)" <de...@db.apache.org> on 2006/09/13 14:13:23 UTC
[jira] Commented: (DERBY-801) Allow parallel access to data files.
[ http://issues.apache.org/jira/browse/DERBY-801?page=comments#action_12434420 ]
Knut Anders Hatlen commented on DERBY-801:
------------------------------------------
Thank you, Anders! I think the patch looks very good, and unless someone objects within a couple of days, I will commit it. Since the patch touches such a critical part of the system, I don't think we should port it to 10.2 this late in the release process.
Derbyall ran cleanly on Solaris 10 x86, Sun JVM 1.5.0.
> Allow parallel access to data files.
> ------------------------------------
>
> Key: DERBY-801
> URL: http://issues.apache.org/jira/browse/DERBY-801
> Project: Derby
> Issue Type: Improvement
> Components: Performance, Store
> Affects 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
> Assigned To: Anders Morken
> Attachments: DERBY-801-v2.patch, DERBY-801-v3.patch, DERBY-801-v4.patch, NIO-RAFContainer-v1.patch
>
>
> 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
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