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Date: Wed, 23 Jul 2008 05:47:32 -0700 (PDT)
From: "Kristian Waagan (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-3731) Improve calculation of refSize in
 ClassSize.java
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    [ https://issues.apache.org/jira/browse/DERBY-3731?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12615999#action_12615999 ] 

Kristian Waagan commented on DERBY-3731:
----------------------------------------

Thanks for looking at the patch, Knut Anders.
Your comments are all valid, I'll incorporate them in the next revision.

I investigated a little more regarding the permissions. Seems Derby isn't allowed to read sun.arch.data.model with the current policy file, but it is allowed to read os.arch for some reason.
Adding code to print the current permissions shows that reading the property os.arch is indeed granted, but it is not in our default policy file. Since I don't know if this is specific for the Sun JVM or not, maybe we should document and add both permissions to the default policy file?

> Improve calculation of refSize in ClassSize.java 
> -------------------------------------------------
>
>                 Key: DERBY-3731
>                 URL: https://issues.apache.org/jira/browse/DERBY-3731
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>            Reporter: Kathey Marsden
>            Priority: Minor
>         Attachments: derby-3731-1a-refsize_from_properties.diff, DERBY-3731_diff.txt
>
>
> java/engine/org/apache/derby/iapi/services/cache/ClassSize.java has a static code block which calculates the size of a reference for the architecture.  This code could be improved by adding garbage collection before measuring memory, to give a consistent  reading.     Also there have been suggestions that we use os.arch or sun.arch.data.model to make the measurement more reliable, especially on 64bit machines.

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