RFR: 8275729: Qualified method names in CodeHeap Analytics

[Volker Simonis]

On Mon, 1 Nov 2021 20:51:39 GMT, Evgeny Astigeevich <duke at openjdk.java.net> wrote:

> This PR changes nmethods names in `METHOD NAMES for CodeHeap` section to be  qualified.
> Testing:
> - `make test TEST="gtest"`:  Passed
> - `make run-test TEST="tier1"`: Passed
> - `make run-test TEST="tier2"`: Passed
> - `make run-test TEST=serviceability/dcmd/compiler/CodeHeapAnalyticsMethodNames.java`: Passed

src/hotspot/share/code/codeHeapState.cpp line 2340:

> 2338: 
> 2339:             Klass* klass = method->method_holder();
> 2340:             assert(klass->is_loader_alive(), "must be alive");

Are you sure `klass` is always valid here and that its class loader has to be alive (i.e. the corresponding class hasn't been unloaded in the meantime)?

In [https://bugs.openjdk.java.net/browse/JDK-8275729](JDK-8275729) you say that the Top50 list already has qualified names but as far as I know, that information is already collected in the aggregation step where it is safe. You now query this information in the reporting step.

I know we had problems due to access to dead methods before (see [JDK-8219586: CodeHeap State Analytics processes dead nmethods](https://bugs.openjdk.java.net/browse/JDK-8219586) and I just want to make sure we don't re-introduce such problems.

Maybe @RealLucy or @fisk can have an additional look?

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PR: https://git.openjdk.java.net/jdk/pull/6200