RFR: JDK-8316691: Heap dump: separate stack traces for mounted virtual threads [v3]

[Serguei Spitsyn]

On Fri, 29 Sep 2023 02:20:10 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] jd...
>
> Alex Menkov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   misspell getRefererId for consistency

src/hotspot/share/services/heapDumper.cpp line 1559:

> 1557:   // Dumps a HPROF_GC_ROOT_JAVA_FRAME subrecord for each local
> 1558:   // Dumps a HPROF_GC_ROOT_JNI_LOCAL subrecord for each JNI local
> 1559:   // Returns the number of Java frames in this thread stack

Q: Is this line of comment just wrong and a leftover from an old version of the fix? Function does not return anything, right?

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PR Review Comment: https://git.openjdk.org/jdk/pull/15869#discussion_r1345032171