The following test failed in the JDK16 CI:

runtime/cds/appcds/dynamicArchive/DynamicLotsOfClasses.java

Here's a snippet from the log file:

----------System.err:(72/4976)*----------
 stdout: [[0.005s][info][cds] optimized module handling: disabled due to incompatible property: jdk.module.addmods.0=ALL-SYSTEM
[0.006s][info][cds] optimized module handling: disabled because bootclasspath was appended
[0.071s][info][cds] trying to map c:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-16+24-1510\\windows-x64-debug.jdk\\jdk-16\\fastdebug\\bin\\server\\classes.jsa
[0.071s][info][cds] Opened archive c:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-16+24-1510\\windows-x64-debug.jdk\\jdk-16\\fastdebug\\bin\\server\\classes.jsa.
[0.071s][info][cds] Archive was created with UseCompressedOops = 1, UseCompressedClassPointers = 1
[0.071s][info][cds] full module graph: disabled because archive was created without full module graph
[0.071s][info][cds] Windows mmap workaround: releasing archive space.
[0.071s][info][cds] Mapped static  region #0 at base 0x0000000800000000 top 0x0000000800010000 (MiscCode)
[0.072s][info][cds] Mapped static  region #1 at base 0x0000000800010000 top 0x0000000800460000 (ReadWrite)
[0.072s][info][cds] Mapped static  region #2 at base 0x0000000800460000 top 0x0000000800bf0000 (ReadOnly)
[0.072s][info][cds] ArchiveRelocationMode == 1: always map archive(s) at an alternative address
[0.072s][info][cds] Unmapping region #0 at base 0x0000000800000000 (MiscCode)
[0.072s][info][cds] Unmapping region #1 at base 0x0000000800010000 (ReadWrite)
[0.072s][info][cds] Unmapping region #2 at base 0x0000000800460000 (ReadOnly)
[0.073s][info][cds] Try to map archive(s) at an alternative address
[0.073s][info][cds] Commit static  region #0 at base 0x00000199d9000000 top 0x00000199d9010000 (MiscCode) exec
[0.073s][info][cds] Mapped static  region #0 at base 0x00000199d9000000 top 0x00000199d9010000 (MiscCode)
[0.073s][info][cds] Commit static  region #1 at base 0x00000199d9010000 top 0x00000199d9460000 (ReadWrite)
[0.077s][info][cds] Mapped static  region #1 at base 0x00000199d9010000 top 0x00000199d9460000 (ReadWrite)
[0.078s][info][cds] Commit static  region #2 at base 0x00000199d9460000 top 0x00000199d9bf0000 (ReadOnly)
[0.085s][info][cds] Mapped static  region #2 at base 0x00000199d9460000 top 0x00000199d9bf0000 (ReadOnly)
[0.097s][info][cds] optimized module handling: disabled
[0.097s][info][cds] full module graph: disabled
[0.098s][info][cds] Unmapping region #3 at base 0x00000199bda70000 (Bitmap)
Loaded classes = 25854
[88.137s][info][cds] Verify Before CDS dynamic dump
#
# A fatal error has been detected by the Java Runtime Environment:
#
#  EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x00007ff89095e80e, pid=104000, tid=98328
#
# JRE version: Java(TM) SE Runtime Environment (16.0+24) (fastdebug build 16-ea+24-1510)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 16-ea+24-1510, mixed mode, sharing, tiered, compressed oops, g1 gc, windows-amd64)
# Problematic frame:
# V  [jvm.dll+0x3be80e]  oopDesc::size_given_klass+0x1e
#
# Core dump will be written. Default location: T:\\testoutput\\test-support\\jtreg_open_test_hotspot_jtreg_hotspot_cds_relocation\\scratch\\2\\hs_err_pid104000.mdmp
#
Unsupported internal testing APIs have been used.

# An error report file with more information is saved as:
# T:\\testoutput\\test-support\\jtreg_open_test_hotspot_jtreg_hotspot_cds_relocation\\scratch\\2\\hs_err_pid104000.log
#
# If you would like to submit a bug report, please visit:
#   https://bugreport.java.com/bugreport/crash.jsp
#

Here's the crashing thread's stack:

---------------  T H R E A D  ---------------

Current thread (0x0000019a22af4290):  GCTaskThread "GC Thread#7" [stack: 0x0000000b20400000,0x0000000b20500000] [id=98328]

Stack: [0x0000000b20400000,0x0000000b20500000],  sp=0x0000000b204ff5d0,  free space=1021k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V  [jvm.dll+0x3be80e]  oopDesc::size_given_klass+0x1e  (oop.inline.hpp:147)
V  [jvm.dll+0x65167d]  HeapRegion::verify+0x13d  (heapRegion.cpp:669)
V  [jvm.dll+0x5cb157]  VerifyRegionClosure::do_heap_region+0x367  (g1HeapVerifier.cpp:406)
V  [jvm.dll+0x654c06]  HeapRegionManager::par_iterate+0x156  (heapRegionManager.cpp:545)
V  [jvm.dll+0x5ccafc]  G1ParVerifyTask::work+0x4c  (g1HeapVerifier.cpp:455)
V  [jvm.dll+0xd51669]  GangWorker::loop+0x89  (workgroup.cpp:279)
V  [jvm.dll+0xc91d44]  Thread::call_run+0x1b4  (thread.cpp:402)
V  [jvm.dll+0xae2ade]  thread_native_entry+0x10e  (os_windows.cpp:476)
C  [ucrtbase.dll+0x1fb80]
C  [KERNEL32.DLL+0x84d4]
C  [ntdll.dll+0x6e871]


siginfo: EXCEPTION_ACCESS_VIOLATION (0xc0000005), reading address 0x0000019fae6dd600


The test task's JVM args are:

-XX:+UnlockDiagnosticVMOptions -XX:ArchiveRelocationMode=1 -Xlog:cds -XX:NativeMemoryTracking=detail

Starting this bug off in hotspot/runtime for initial triage.