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https://issues.apache.org/jira/browse/DERBY-5503?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13150641#comment-13150641
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Mike Matrigali commented on DERBY-5503:
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Derby pays the encryption cost either when a page comes off disk and goes into
the derby cache, or when a dirty page moves from cache
to disk. There is also an encryption cost for every log record written, which
would be a normal part of a benchmark. There is also a cost for
every log record read, but this cost is rarely measured in a benchmark as it
would only happen during abort transaction and/or database recovery at startup
after an abnormal exit.
So worst case for this comparison if you can come up with an experiment where
the No encryption case is running 100% cpu on
all available processors per thread, and the size of the experiment does not
get a lot of derby cache hits.
Update benchmarks are hard to get consistent reproducible results unless you
run for a long time as derby separates the I/O(and associated
encryption cost) from the transaction that does the update. Then your results
depend whether you happen to hit a checkpoint while you are
measuring or not.
A select benchmark that loads the data as part of the setup probably gives fair
results across each run. For worst case you should pick the
size of the data so it is likely to sit in the OS cache after creation, thus
making the derby cache faults from disk really not be I/O's thus making
the test cpu bound. On the other hand one could come up with a best case
scenario where all operations happen in cache and there should
be no degredation.
> Measure the performance degradation incurred by encrypting Derby databases
> --------------------------------------------------------------------------
>
> Key: DERBY-5503
> URL: https://issues.apache.org/jira/browse/DERBY-5503
> Project: Derby
> Issue Type: Task
> Components: Store
> Affects Versions: 10.9.0.0
> Reporter: Rick Hillegas
>
> It would be good to measure the performance degradation incurred by Derby's
> encryption.
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