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https://issues.apache.org/jira/browse/DERBY-4963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12980027#action_12980027
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Knut Anders Hatlen commented on DERBY-4963:
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I ran the single-record update performance test in derbyTesting.jar on
Solaris/JDK6 with the write-cache disabled, and I didn't see any performance
loss with the patch. Solaris is one of the platforms on which rws vs rwd, or
sync(true) vs sync(false), does make a difference, so it seems you're right
that the code path in question is not executed on recent JVMs. If there had
been a change from one write operation to two write operations per log flush,
the single-record update performance test should have detected it.
> Revert to FileDescriptor#sync from FileChannel#force to improve interrupt
> resilience
> ------------------------------------------------------------------------------------
>
> Key: DERBY-4963
> URL: https://issues.apache.org/jira/browse/DERBY-4963
> Project: Derby
> Issue Type: Improvement
> Components: Store
> Reporter: Dag H. Wanvik
> Assignee: Dag H. Wanvik
> Fix For: 10.8.0.0
>
> Attachments: derby-4963-1.diff, derby-4963-1.stat
>
>
> FileChannel.force is interruptable, and we really don't want to be
> interrupted when we flush the log file. Happily, on most platforms, we use
> the "rws"/"rwd" file open mask which makes the writes thjemselves
> synchronized, so no subsequent explicit file level sync is needed anyway.
> DirFile4#getRandowmAccessFile should use plain DirRandomAccessFile instead of
> the current DirRandomAccessFile4. This will make StorageRandomAccessFile#sync
> map to FileDescriptor#sync instead of FileChannel#force (also for NIO
> supporting platforms).
> Since FileDescriptor#sync does not allow synching file data only (it also
> synchronizes metadata), those platforms which do not support write
> synchronization will experience a performance drop, but this is the price we
> have to pay to survive interrupts without shutting down the database on those
> platforms.
> Users which experience this as a problem, should update to a newer JVM which
> does support "rws"/"rwd" in the mode argument to java.io.RandomAccessFile
> (http://download.oracle.com/javase/6/docs/api/java/io/RandomAccessFile.html#RandomAccessFile(java.io.File,%20java.lang.String).
> Cf. also discussion on
> https://issues.apache.org/jira/browse/DERBY-4741?focusedCommentId=12977862&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12977862
> .
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