RFR (M): 8014659: NPG: performance counters for compressed klass space

Mikael Gerdin mikael.gerdin at oracle.com
Thu Aug 15 13:54:33 UTC 2013


On 08/14/2013 04:49 PM, Erik Helin wrote:
> Hi all,
> this change adds performance counters for compressed class space.
> Webrev:
> http://cr.openjdk.java.net/~ehelin/8014659/webrev.00/
> Changes to hotspot:
> The main changes are in metaspaceCounters.hpp and metaspaceCounters.cpp,
> where the class MetaspaceCounters has been split up into
> MetaspaceCounters and MetaspacePerfCounters. MetaspaceCounters now owns
> an instance of MetaspacePerfCounters. The class
> CompressedClassSpaceCounters has been added which also has its own
> instance of MetaspacePerfCounters. MetaspacePerfCounters initializes and
> updates the actual performance counters.

I'm a bit concerned about the exception handling in the perf variable 
creation. But it appears to be similar to the other places where perf 
variables are created.

Creating a 0-reporting perf counter if -UseCompressedKlassPointers seems 
consistent with the rest of the code.

I'd say this is fine, but as Coleen mentioned you should verify this 
with Harold's change for CDS+CompressedOops.

> The changes in metaspace.hpp/cpp were needed to get some additional data
> from the metaspace data structures. The method
> free_chunks_in_total(mdtype) was made public and the method
> free_bytes(mdtype) was added. Some common functionality was extracted
> into get_space_list(mdtype) which got rid of some duplicated code.
> The changes in:
> - g1MonitorinSupport.cpp
> - parallelScavengeHeap.cpp
> - genCollectedHeap.cpp
> - universe.cpp
> are only "one-liners" that either update or initialize the new performance
> counters.
> Changes to the testlibrary:
> - Added Asserts.java for writing asserts like "assertTrue",
>    "assertEquals", etc.
> - Added PerfCounter.java and PerfCounters.java to make it easy to
>    inspect performance counters for the currently running VM.
> - Added InputArguments.java so a test can check the arguments it got
>    passed.
> - Added InMemoryJavaCompiler.java for compiling a string into bytecode.
>    Useful for loading classes generated at runtime without using files.
> - Added ByteCodeLoader.java for defining a new class when you already
>    have the bytecode.

The test code looks fine.

> Testing:
> - Added the new test TestMetaspacePerfCounters.java
> - JPRT
> Bug:
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8014659
> Thanks,
> Erik

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