[ http://issues.apache.org/jira/browse/DERBY-2118?page=all ]
Dyre Tjeldvoll updated DERBY-2118:
----------------------------------
Attachment: cleanup_flat_profile.txt
I have attached the flat profile listing from my profiler (Sun Studio11
collect/analyzer) from a run with Dan's clearLimit-patch. Maybe if others also
see the numbers they can propose other performance improvements.
> Change some boundary checks in ArrayInputStream to ASSERTs to improve
> performance
> ---------------------------------------------------------------------------------
>
> Key: DERBY-2118
> URL: http://issues.apache.org/jira/browse/DERBY-2118
> Project: Derby
> Issue Type: Improvement
> Components: Performance
> Affects Versions: 10.2.1.6
> Reporter: Dyre Tjeldvoll
> Priority: Trivial
> Fix For: 10.3.0.0
>
> Attachments: cleanup_flat_profile.txt,
> d2018_clearlimit_cleanup_diff.txt, derby-2118.diff, derby-2118.stat,
> derby-2118.v2.diff
>
>
> Profiling shows that a significant amount of CPU is spent doing boundary
> checking in ArrayInputStream.setPosition() and ArrayInputStream.setLimit().
> These checks appear to be there to detect error conditions, so it seems more
> appropriate to make them ASSERTs. Especially since they are so expensive.
> DTrace analysis seems to confirm that these methods get called very
> frequently:
> Knut Anders Hatlen wrote the following in a message on derby-dev:
> FYI, I just ran the DERBY-1961 test clients and traced them with a
> DTrace script that printed how often each method was called. For the
> join client, ArrayInputStream.setPosition() was the most frequently
> called method (43837.7 calls/tx). For the single-record select client,
> it was third (58.4 calls/tx), only beaten by Object.<init>() and
> DDMWriter.ensureLength(). I think this means that setPosition() is the
> engine method that is most frequently called, at least in read-mostly
> transactions. ArrayInputStream.setLimit() also appeared near the top
> of the list. See http://wiki.apache.org/db-derby/Derby1961MethodCalls
> for the details.
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