RFR: JDK-8316691: Heap dump: separate stack traces for mounted virtual threads

[David Holmes]

On Thu, 21 Sep 2023 20:06:13 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

> This is subtask of JDK-8299426: Heap dump does not contain virtual Thread stack references
> The change:
> - reorganize thread-related code/prepare it to use for unmounted vthreads:
>   - new ThreadDumper class caches stack frames, thread serial num, frame serial number (trace serial number is calculated from thread serial);
>     ThreadDumper objects for all platform/carrier and mounted virtual threads are cached instead of ThreadStackTrace objects (they are created during HPROF_FRAME/HPROF_TRACE dumping, used lated for writing HPROF_GC_ROOT_THREAD_OBJ/HPROF_GC_ROOT_JAVA_FRAME/HPROF_GC_ROOT_JNI_LOCAL subrecords);
>   - new helper class JavaStackRefDumper to dump references from threadf stack;
> - separate track traces for mounted virtual threads:
>   - separate HPROF_FRAME/HPROF_TRACE records for mounted vthreads and carrier threads;
>   - separate HPROF_GC_ROOT_THREAD_OBJ/HPROF_GC_ROOT_JAVA_FRAME/HPROF_GC_ROOT_JNI_LOCAL subrecords;
> - updated hprof parser test lib to collect data about threads (HPROF_GC_ROOT_THREAD_OBJ subrecords) and corresponding stack traces and stack references.
> 
> Testing - tier1-tier3, new test
> 
> Output of the test for VtreadInHeapDumpTarg$VthreadMounted thread
> without the fix:
> `thread 0x8101be90, 16 frames
>   - [0] VtreadInHeapDumpTarg$VthreadMounted.run()V (VtreadInHeapDump.java:127)
>       Java Local Reference: VtreadInHeapDumpTarg$VthreadMounted
>       Java Local Reference: VtreadInHeapDumpTarg$VThreadMountedReferenced
>   - [1] java.lang.Thread.runWith(Ljava/lang/Object;Ljava/lang/Runnable;)V (Thread.java:1583)
>       Java Local Reference: java.lang.VirtualThread
>       Java Local Reference: java.lang.Class
>       Java Local Reference: VtreadInHeapDumpTarg$VthreadMounted
>   - [2] java.lang.VirtualThread.run(Ljava/lang/Runnable;)V (VirtualThread.java:309)
>       Java Local Reference: java.lang.VirtualThread
>       Java Local Reference: VtreadInHeapDumpTarg$VthreadMounted
>       Java Local Reference: java.lang.Class
>   - [3] java.lang.VirtualThread$VThreadContinuation$1.run()V (VirtualThread.java:190)
>       Java Local Reference: java.lang.VirtualThread$VThreadContinuation$1
>   - [4] jdk.internal.vm.Continuation.enter0()V (Continuation.java:320)
>       Java Local Reference: java.lang.VirtualThread$VThreadContinuation
>   - [5] jdk.internal.vm.Continuation.enter(Ljdk/internal/vm/Continuation;Z)V (Continuation.java:312)
>       Java Local Reference: java.lang.VirtualThread$VThreadContinuation
>   - [6] jdk.internal.vm.Continuation.enterSpecial(Ljdk/internal/vm/Continuatio...

test/hotspot/jtreg/serviceability/jvmti/vthread/HeapDump/VtreadInHeapDump.java line 1:

> 1: /*

The file/class name is wrong Vtread instead of VThread

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PR Review Comment: https://git.openjdk.org/jdk/pull/15869#discussion_r1338145621