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From "Anders Morken (JIRA)" <derby-...@db.apache.org>
Subject [jira] Updated: (DERBY-801) Allow parallel access to data files.
Date Mon, 31 Jul 2006 21:14:16 GMT
     [ http://issues.apache.org/jira/browse/DERBY-801?page=all ]

Anders Morken updated DERBY-801:
--------------------------------

    Attachment: DERBY-801-v2.patch

DERBY-801-v2.patch is what I've got now. It's not anything very new since the previous patch,
but it's a bit cleaner - and I've spent a lot of time pondering if what I've done here is
safe. I think it mostly is. I'm sorry this has taken such an awful lot of time - I've been
very busy with my day job this summer, and I haven't really had the time to sit down and do
any proper work on this. Anyway, except for number 2. in my comment above, I think I've mostly
addressed what I worried most about in the last patch. I'd appreciate any comments and suggestions
for further improvement on this one. It passes storeall except for store/TransactionTable.sql
which also fails in a clean trunk checkout. Thanks! =)

> 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, 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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