[11u] RFR: 8214542: JFR: Old Object Sample event slow on a deep heap in debug builds

[Langer, Christoph]

Hi,

please help reviewing the backport of this JFR related bugfix to JDK11.

Bug: https://bugs.openjdk.java.net/browse/JDK-8214542
Original Change: http://hg.openjdk.java.net/jdk/jdk13/rev/49102ba8cf14
Webrev: http://cr.openjdk.java.net/~clanger/webrevs/8214542.11u-dev.0/

The original patch did not apply cleanly. There were some rejects: http://cr.openjdk.java.net/~clanger/webrevs/8214542.11u-dev.0/8214542.rejects.patch

I had to resolve the following files:
src/hotspot/share/jfr/leakprofiler/chains/rootSetClosure.cpp

src/hotspot/share/jfr/leakprofiler/emitEventOperation.hpp

src/hotspot/share/jfr/leakprofiler/leakProfiler.hpp

src/hotspot/share/jfr/leakprofiler/startOperation.hpp

src/hotspot/share/jfr/leakprofiler/stopOperation.hpp

src/hotspot/share/jfr/recorder/service/jfrRecorderService.cpp

src/hotspot/share/runtime/vmOperations.hpp

Resolving was quite straightforward. In jdk11u-dev, the file src/hotspot/share/runtime/vmOperations.hpp is still called src/hotspot/share/runtime/vm_operations.hpp.

With this patch applied, no regressions were observed in SAP's test infrastructure. So I tend to say it works. But it would be good to get this verified by somebody else who has some more knowledge in the JFR area.

I'll also request the backport of JDK-8228834 and push it together with this patch because it is linked to bug JDK-8214542 as regression. It was also included in my testing.

Thanks
Christoph