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Date: Mon, 13 Nov 2006 11:54:39 -0800 (PST)
From: "Anders Morken (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Updated: (DERBY-801) Allow parallel access to data files.
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     [ http://issues.apache.org/jira/browse/DERBY-801?page=3Dall ]

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

    Attachment: DERBY-801-7.patch

This patch (DERBY-801-7.patch) turns the DEBUG_PRINT messages in RAFContain=
er4 into assertions guarding the method entry points. Dunno if they're of a=
ny use now, but if they catch a bug later, they could be worth the overhead=
 in debug builds. =3D)

M      java/engine/org/apache/derby/impl/store/raw/data/RAFContainer4.java

 RAFContainer4.java |   24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

Anything else I need to do before marking this one as resolved? =3D)

> 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, 10.1.2.1
>         Environment: Any
>            Reporter: =C3=98ystein Gr=C3=B8vlen
>         Assigned To: Anders Morken
>         Attachments: DERBY-801-6.patch, DERBY-801-7.patch, DERBY-801-v2.p=
atch, DERBY-801-v3.patch, DERBY-801-v4.patch, DERBY-801-v5.patch, NIO-RAFCo=
ntainer-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 obje=
ct
>         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-adv=
ice-t756863.html

--=20
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