Add profiler counters for time spent in stack unwinding

[bric3]

What does this PR do?:

Use TSC time counters for unwinding.

How to test the change?:

For Datadog employees:

• If this PR touches code that signs or publishes builds or packages, or handles
  credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.
• JIRA: PROF-11368

Unsure? Have a question? Request a review!

[github-actions]

🔧 Report generated by pr-comment-scanbuild

Scan-Build Report

User:	runner@fv-az788-802
Working Directory:	/home/runner/work/java-profiler/java-profiler/ddprof-lib/src/test/make
Command Line:	make -j4 clean all
Clang Version:	Ubuntu clang version 18.1.3 (1ubuntu1)
Date:	Fri Mar 21 12:53:47 2025

Bug Summary

Bug Type	Quantity	Display?
All Bugs	7
Logic error
Dereference of null pointer	3
Suspicious operation
Bitwise shift	1
Unused code
Dead initialization	2
Dead nested assignment	1

Reports

Bug Group	Bug Type ▾	File	Function/Method	Line	Path Length
Suspicious operation	Bitwise shift	vmStructs.cpp	find	902	16
Unused code	Dead initialization	javaApi.cpp	Java_com_datadoghq_profiler_JavaProfiler_getStatus0	116	1
Unused code	Dead initialization	stackWalker.cpp	walkDwarf	160	1
Unused code	Dead nested assignment	vmStructs.cpp	checkNativeBinding	1007	1
Logic error	Dereference of null pointer	safeAccess.h	load	33	18
Logic error	Dereference of null pointer	symbols_linux.h	ElfParser	144	28
Logic error	Dereference of null pointer	flightRecorder.cpp	flush	1504	8

[github-actions]

🔧 Report generated by pr-comment-cppcheck

CppCheck Report

Warnings (7)

• The class 'RecordingBuffer' defines member function with name 'flushIfNeeded' also defined in its parent class 'Buffer'.
• Obsolete function 'alloca' called.
• Member variable 'ScopeDesc::_stream' is not initialized in the constructor.
• Member variable 'ScopeDesc::_method_offset' is not initialized in the constructor.
• Member variable 'ScopeDesc::_bci' is not initialized in the constructor.
• Member variable 'ElfParser::_vaddr_diff' is not initialized in the constructor.
• Either the condition 'vm_thread' is redundant or there is possible null pointer dereference: vm_thread.

Style Violations (398)

• The class 'NativeFunc' does not declare a constructor although it has private member variables which likely require initialization.
• Class 'Arguments' has a constructor with 1 argument that is not explicit.
• Local variable 'count' shadows outer function
• Local variable 'jni' shadows outer function
• Variable 'cb1' can be declared as pointer to const
• Variable 'cb2' can be declared as pointer to const
• struct member 'Multiplier::symbol' is never used.
• struct member 'Multiplier::multiplier' is never used.
• class member 'Error::OK' is never used.
• Class 'AsyncSampleMutex' has a constructor with 1 argument that is not explicit.
• Class 'SpinLock' has a constructor with 1 argument that is not explicit.
• Local variable 'size' shadows outer function
• Local variable 'prev' shadows outer function
• Variable 'keys' can be declared as pointer to const
• Parameter 'frames' can be declared as pointer to const
• Parameter 'frames' can be declared as pointer to const
• Variable 'keys' can be declared as pointer to const
• struct member 'CallTrace::truncated' is never used.
• struct member 'CallTrace::num_frames' is never used.
• class member 'CallTraceStorage::_current_table' is never used.
• class member 'CallTraceStorage::_overflow' is never used.
• class member 'CallTraceStorage::_lock' is never used.
• Local variable 'i' shadows outer variable
• Parameter 'prefixes' can be declared as reference to const
• Variable 'fd1' can be declared as pointer to const
• Variable 'fd2' can be declared as pointer to const
• Parameter 'name' can be declared as pointer to const
• Consider using std::transform algorithm instead of a raw loop.
• struct member 'Tag::value' is never used.
• class member 'Context::spanId' is never used.
• class member 'Context::rootSpanId' is never used.
• class member 'Context::checksum' is never used.
• struct member 'ContextPage::capacity' is never used.
• struct member 'ContextPage::storage' is never used.
• class member 'Contexts::_max_pages' is never used.
• class member 'Contexts::_pages' is never used.
• The function 'check' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'start' overrides a function in a base class but is not marked with a 'override' specifier.
• class member 'Shims::_tid_setter_ref' is never used.
• Class 'Dictionary' has a constructor with 1 argument that is not explicit.
• struct member 'DictRow::keys' is never used.
• struct member 'DictRow::next' is never used.
• Operator '|' with one operand equal to zero is redundant.
• Local variable 'table' shadows outer function
• Local variable 'pc_off' shadows outer variable
• Variable 'table' can be declared as pointer to const
• Operator '|' with one operand equal to zero is redundant.
• struct member 'FrameDesc::cfa' is never used.
• struct member 'FrameDesc::fp_off' is never used.
• struct member 'FrameDesc::pc_off' is never used.
• struct member 'FrameDesc::empty_frame' is never used.
• struct member 'FrameDesc::default_frame' is never used.
• class member 'DwarfParser::_name' is never used.
• class member 'DwarfParser::_image_base' is never used.
• class member 'DwarfParser::_capacity' is never used.
• class member 'DwarfParser::_prev' is never used.
• class member 'DwarfParser::_code_align' is never used.
• class member 'DwarfParser::_data_align' is never used.
• Class 'WallClockEpochEvent' has a constructor with 1 argument that is not explicit.
• class member 'LockEvent::_start_time' is never used.
• class member 'LockEvent::_end_time' is never used.
• class member 'LockEvent::_address' is never used.
• class member 'LockEvent::_timeout' is never used.
• class member 'ObjectLivenessEvent::_alloc' is never used.
• class member 'ObjectLivenessEvent::_skipped' is never used.
• class member 'ObjectLivenessEvent::_start_time' is never used.
• class member 'ObjectLivenessEvent::_age' is never used.
• class member 'ObjectLivenessEvent::_ctx' is never used.
• struct member 'QueueTimeEvent::_start' is never used.
• struct member 'QueueTimeEvent::_end' is never used.
• struct member 'QueueTimeEvent::_task' is never used.
• struct member 'QueueTimeEvent::_scheduler' is never used.
• struct member 'QueueTimeEvent::_origin' is never used.
• struct member 'QueueTimeEvent::_queueType' is never used.
• struct member 'QueueTimeEvent::_queueLength' is never used.
• The class 'VirtualSpaceSummary' does not declare a constructor although it has private member variables which likely require initialization.
• The class 'GCHeapSummary' does not declare a constructor although it has private member variables which likely require initialization.
• The class 'CollectedHeap' does not declare a constructor although it has private member variables which likely require initialization.
• Class 'Element' has a constructor with 1 argument that is not explicit.
• Class 'NoField' has a constructor with 1 argument that is not explicit.
• Class 'MutexLocker' has a constructor with 1 argument that is not explicit.
• Class 'MethodList' has a constructor with 1 argument that is not explicit.
• Class 'ScopeDesc' has a constructor with 1 argument that is not explicit.
• The function 'is_nofield' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'check' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'start' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'stop' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'interval' overrides a function in a base class but is not marked with a 'override' specifier.
• Condition 'enabled()' is always false
• Condition 'usage._maxSize==-1' is always false
• Condition 'counters' is always false
• Condition 'i<names.size()' is always false
• Condition '!TSC::initialized()' is always false
• The scope of the variable 'class_name_id' can be reduced.
• The scope of the variable 'method_name_id' can be reduced.
• The scope of the variable 'method_sig_id' can be reduced.
• Local variable 'start' shadows outer function
• Parameter 'frame' can be declared as reference to const
• Variable 'strings' can be declared as reference to const
• Parameter 'args' can be declared as reference to const
• Parameter 'constants' can be declared as reference to const
• Parameter 'ptr' can be declared as pointer to const. However it seems that 'load32' is a callback function, if 'ptr' is declared with const you might also need to cast function pointer(s).
• Variable 'methods' can be declared as pointer to const
• Parameter 'func' can be declared as pointer to const
• Variable 'counters' can be declared as pointer to const
• Parameter 'event' can be declared as pointer to const
• Parameter 'event' can be declared as pointer to const
• Parameter 'event' can be declared as pointer to const
• Parameter 'event' can be declared as pointer to const
• Parameter 'event' can be declared as pointer to const
• Parameter 'event' can be declared as pointer to const
• Parameter 'event' can be declared as pointer to const
• Parameter 'event' can be declared as pointer to const
• Variable 'class_name_id' is assigned a value that is never used.
• Variable 'method_name_id' is assigned a value that is never used.
• Variable 'method_sig_id' is assigned a value that is never used.
• Parameter 'ptr' can be declared as pointer to const
• struct member 'CpuTime::real' is never used.
• struct member 'CpuTime::user' is never used.
• struct member 'CpuTime::system' is never used.
• struct member 'CpuTimes::proc' is never used.
• struct member 'CpuTimes::total' is never used.
• class member 'Recording::_agent_properties' is never used.
• class member 'Recording::_jvm_args' is never used.
• class member 'Recording::_jvm_flags' is never used.
• class member 'Recording::_java_command' is never used.
• class member 'Recording::_fd' is never used.
• class member 'Recording::_start_time' is never used.
• class member 'Recording::_recording_start_time' is never used.
• class member 'Recording::_start_ticks' is never used.
• class member 'Recording::_recording_start_ticks' is never used.
• class member 'Recording::_stop_time' is never used.
• class member 'Recording::_stop_ticks' is never used.
• class member 'Recording::_base_id' is never used.
• class member 'Recording::_bytes_written' is never used.
• class member 'Recording::_tid' is never used.
• class member 'Recording::_available_processors' is never used.
• class member 'Recording::_recorded_lib_count' is never used.
• class member 'Recording::_cpu_monitor_enabled' is never used.
• class member 'Recording::_last_times' is never used.
• class member 'FlightRecorder::_filename' is never used.
• The function 'name' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'interval' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'check' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'start' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'stop' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'enableEvents' overrides a function in a base class but is not marked with a 'override' specifier.
• class member 'ITimer::_cstack' is never used.
• struct member 'jvmtiFrameInfoExtended::native_frame_address' is never used.
• struct member 'jvmtiStackInfoExtended::frame_buffer' is never used.
• class member 'J9Ext::InstrumentableObjectAlloc_id' is never used.
• The class 'J9WallClock' does not declare a constructor although it has private member variables which likely require initialization.
• The function 'name' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'interval' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'start' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'stop' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'enableEvents' overrides a function in a base class but is not marked with a 'override' specifier.
• class member 'J9WallClock::_max_stack_depth' is never used.
• class member 'J9WallClock::_running' is never used.
• Class 'ReservoirSampler' has a constructor with 1 argument that is not explicit.
• The function 'name' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'interval' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'enableEvents' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'start' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'stop' overrides a function in a base class but is not marked with a 'override' specifier.
• Variable 'value' can be declared as pointer to const
• Variable 'ret' is assigned a value that is never used.
• class member 'JfrMetadata::_initialized' is never used.
• class member 'JVM::_is_readable_pointer_resolved' is never used.
• class member 'JVM::_is_readable_pointer' is never used.
• class member 'VirtualSpaceSummary::_committed_end' is never used.
• class member 'GCHeapSummary::vptr' is never used.
• class member 'CollectedHeap::vptr' is never used.
• class member 'CollectedHeap::_gc_heap_log' is never used.
• class member 'CollectedHeap::_capacity_at_last_gc' is never used.
• class member 'CollectedHeap::_used_at_last_gc' is never used.
• struct member 'Chunk::prev' is never used.
• struct member 'Chunk::offs' is never used.
• struct member 'Chunk::_padding' is never used.
• class member 'LinearAllocator::_chunk_size' is never used.
• class member 'LinearAllocator::_tail' is never used.
• class member 'LinearAllocator::_reserve' is never used.
• Local variable 'start' shadows outer function
• Local variable 'start' shadows outer function
• Parameter 'args' can be declared as reference to const
• Parameter 'event' can be declared as reference to const
• Unused variable: kept_classes
• struct member 'TrackingEntry::alloc' is never used.
• struct member 'TrackingEntry::skipped' is never used.
• struct member 'TrackingEntry::call_trace_id' is never used.
• struct member 'TrackingEntry::ctx' is never used.
• class member 'LivenessTracker::MAX_TRACKING_TABLE_SIZE' is never used.
• class member 'LivenessTracker::MIN_SAMPLING_INTERVAL' is never used.
• class member 'LivenessTracker::_table_lock' is never used.
• Condition 'level>=_level' is always true
• Parameter 'args' can be declared as reference to const
• class member 'Log::_file' is never used.
• class member 'Log::LEVEL_NAME' is never used.
• class member 'ObjectSampler::CONFIG_UPDATE_CHECK_PERIOD_SECS' is never used.
• class member 'JitWriteProtection::_prev' is never used.
• class member 'JitWriteProtection::_restore' is never used.
• class member 'OS::page_size' is never used.
• class member 'OS::page_mask' is never used.
• The function 'rewind' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'next' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'size' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'check' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'start' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'enableEvents' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'registerThread' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'unregisterThread' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'interval' overrides a function in a base class but is not marked with a 'override' specifier.
• The function 'enableEvents' overrides a function in a base class but is identical to the overridden function
• The function 'registerThread' overrides a function in a base class but is identical to the overridden function
• The function 'unregisterThread' overrides a function in a base class but is identical to the overridden function
• Condition 'i<PROBE_SP_LIMIT' is always false
• Condition 'event_name==NULL' is always true
• Parameter 'args' can be declared as reference to const
• Parameter 'java_ctx' can be declared as pointer to const
• Variable 'error' is assigned a value that is never used.
• Variable 'error' is assigned a value that is never used.
• Variable 'error' is assigned a value that is never used.
• Variable 'error' is assigned a value that is never used.
• Condition 'length>0' is always false
• class member 'Profiler::_signals_initialized' is never used.
• class member 'Profiler::_class_map_lock' is never used.
• class member 'Profiler::_locks' is never used.
• Condition 'strcmp(name,"forward_copy_longs")==0' is always false
• Condition 'strcmp(name,"backward_copy_longs")==0' is always false
• Variable 'ip' can be declared as pointer to const
• Parameter 'ip' can be declared as pointer to const
• Variable 'ip' can be declared as pointer to const
• Parameter 'pc' can be declared as pointer to const
• Unused private function: 'StackFrame::withinCurrentStack'
• Variable 'ip' can be declared as pointer to const
• Parameter 'entry' can be declared as pointer to const
• Variable 'ip' can be declared as pointer to const
• Parameter 'pc' can be declared as pointer to const
• Variable 'ip' can be declared as pointer to const
• Variable 'ip' can be declared as pointer to const
• Variable 'entry' can be declared as pointer to const
• Parameter 'pc' can be declared as pointer to const
• Parameter 'sp' can be declared as reference to const
• Variable 'inst' can be declared as pointer to const
• Variable 'inst' can be declared as pointer to const
• Parameter 'pc' can be declared as pointer to const
• Variable 'ip' can be declared as pointer to const
• Parameter 'pc' can be declared as pointer to const
• Local variable 'pc' shadows outer function
• Return value 'ptr>(const void*)-DEAD_ZONE' is always true
• Condition '!inDeadZone(method)' is always false
• Condition '!inDeadZone(method_id)' is always false
• Condition 'inDeadZone(pc)' is always true
• Condition 'inDeadZone(pc)' is always true
• Condition 'is_plausible_interpreter_frame' is always false
• Condition 'inDeadZone(pc)' is always true
• The comparison 'EMPTY_FRAME_SIZE > 0' is always false.
• The comparison 'EMPTY_FRAME_SIZE > 0' is always false.
• The scope of the variable 'prev_sp' can be reduced.
• Local variable 'frame' shadows outer variable
• Variable 'page_start' is assigned a value that is never used.
• The comparison 'EMPTY_FRAME_SIZE > 0' is always false.
• The comparison 'EMPTY_FRAME_SIZE > 0' is always false.
• Class 'SymbolDesc' has a constructor with 1 argument that is not explicit.
• Class 'MemoryMapDesc' has a constructor with 1 argument that is not explicit.
• Local variable 'section' shadows outer function
• Local variable 'section' shadows outer function
• Local variable 'section' shadows outer function
• Variable 'ident' can be declared as pointer to const
• Parameter 'section' can be declared as pointer to const
• Variable 'checked' can be declared as pointer to const
• Variable 'pheader' can be declared as pointer to const
• Variable 'sym' can be declared as pointer to const
• Variable 'sym' can be declared as pointer to const
• Variable 'chain' can be declared as pointer to const
• Variable 'plt' can be declared as pointer to const
• Variable 'note' can be declared as pointer to const
• Variable 'sym' can be declared as pointer to const
• Variable 'sym' can be declared as pointer to const
• Local variable 'tid' shadows outer function
• Local variable 'tid' shadows outer function
• class member 'ProfiledThread::_buffer_size' is never used.
• class member 'ProfiledThread::_buffer' is never used.
• Local variable 'word' shadows outer function
• class member 'ThreadFilter::_max_bitmaps' is never used.
• class member 'ThreadInfo::_thread_names' is never used.
• class member 'ThreadInfo::_thread_ids' is never used.
• class member 'Trap::_page_start' is never used.
• Local variable 'frequency' shadows outer function
• Variable 'idx' can be declared as pointer to const
• Parameter 'prop_value' can be declared as pointer to const
• Variable 'flag_addr' can be declared as pointer to const
• Parameter 'options' can be declared as pointer to const
• struct member 'ASGCT_CallTrace::env' is never used.
• struct member 'ASGCT_CallTrace::frames' is never used.
• struct member 'VMManagement::unused' is never used.
• struct member 'JVMTIFunctions::unused1' is never used.
• struct member 'JVMTIFunctions::unused2' is never used.
• struct member 'JavaFullVersion::major' is never used.
• struct member 'JavaFullVersion::update' is never used.
• class member 'VM::_can_intercept_binding' is never used.
• class member 'VM::_libjvm' is never used.
• class member 'VM::_libjava' is never used.
• class member 'VM::_asyncGetCallTrace' is never used.
• The scope of the variable 'delayedCounter' can be reduced.
• Local variable 'type' shadows outer function
• Parameter 'ptr' can be declared as pointer to const. However it seems that 'load32' is a callback function, if 'ptr' is declared with const you might also need to cast function pointer(s).
• Variable 'code_heap_array' can be declared as pointer to const
• Variable 'blob' can be declared as pointer to const
• Parameter 'vm_thread' can be declared as pointer to const
• Variable 'segmap' can be declared as pointer to const
• Variable 'type_name' can be declared as pointer to const
• Variable 'pcd_end' can be declared as pointer to const
• Consider using std::any_of, std::all_of, std::none_of, or std::accumulate algorithm instead of a raw loop.
• Variable 'error' is assigned a value that is never used.
• class member 'VMStructs::_has_native_thread_id' is never used.
• class member 'VMStructs::_class_loader_data_next_offset' is never used.
• class member 'VMStructs::_scopes_pcs_offset' is never used.
• class member 'VMStructs::_constmethod_constants_offset' is never used.
• class member 'VMStructs::_constmethod_idnum_offset' is never used.
• class member 'VMStructs::_pool_holder_offset' is never used.
• class member 'VMStructs::_array_data_offset' is never used.
• class member 'VMStructs::_code_heap_segmap_offset' is never used.
• class member 'VMStructs::_code_heap_segment_shift' is never used.
• class member 'VMStructs::_heap_block_used_offset' is never used.
• class member 'VMStructs::_vs_low_bound_offset' is never used.
• class member 'VMStructs::_vs_high_bound_offset' is never used.
• class member 'VMStructs::_flag_type_offset' is never used.
• class member 'VMStructs::_flags_addr' is never used.
• class member 'VMStructs::_flag_count' is never used.
• class member 'VMStructs::_flag_size' is never used.
• class member 'VMStructs::_code_heap_low_addr' is never used.
• class member 'VMStructs::_code_heap_high_addr' is never used.
• class member 'VMStructs::_klass_offset_addr' is never used.
• class member 'VMStructs::_narrow_klass_base_addr' is never used.
• class member 'VMStructs::_narrow_klass_base' is never used.
• class member 'VMStructs::_narrow_klass_shift_addr' is never used.
• class member 'VMStructs::_narrow_klass_shift' is never used.
• class member 'VMStructs::_collected_heap' is never used.
• class member 'VMStructs::_collected_heap_reserved_offset' is never used.
• class member 'VMStructs::_region_start_offset' is never used.
• class member 'VMStructs::_region_size_offset' is never used.
• class member 'VMStructs::_markword_klass_shift' is never used.
• class member 'VMStructs::_markword_monitor_value' is never used.
• class member 'VMStructs::_unsigned5_base' is never used.
• class member 'VMStructs::_call_stub_return_addr' is never used.
• class member 'VMStructs::_find_flag_func' is never used.
• class member 'VMStructs::_is_valid_method_func' is never used.
• class member 'HeapUsage::is_jmx_attempted' is never used.
• class member 'PcDesc::_pc' is never used.
• class member 'PcDesc::_scope_offset' is never used.
• class member 'PcDesc::_obj_offset' is never used.
• class member 'PcDesc::_flags' is never used.
• Local variable 'interval' shadows outer function
• Variable 'context' can be declared as reference to const
• struct member 'ThreadEntry::native' is never used.
• The function 'patchImport' is never used.
• The function 'getCounter' is never used.
• The function 'supported' is never used.
• The function 'updateCounter' is never used.
• The function 'deallocateLineNumberTable' is never used.
• The function 'copyTo' is never used.
• The function 'cpuMonitorCycle' is never used.
• The function 'appendRecording' is never used.
• The function 'writeListSetting' is never used.
• The function 'active' is never used.
• The function 'units' is never used.
• The function 'GetJ9vmThread' is never used.
• The function 'is_readable_pointer' is never used.
• The function '_min' is never used.
• The function 'trace' is never used.
• The function 'waitUntil' is never used.
• The function 'notify' is never used.
• The function 'cputime' is never used.
• The function 'ntoh64' is never used.
• The function 'schedPolicy' is never used.
• The function 'fileSize' is never used.
• The function 'flushJfr' is never used.
• The function 'restart' is never used.
• The function 'arg0' is never used.
• The function 'arg2' is never used.
• The function 'jarg0' is never used.
• The function 'ret' is never used.
• The function 'clearParsingCaches' is never used.
• The function 'isDeepCrashHandler' is never used.
• The function 'getThreadId' is never used.
• The function 'assign' is never used.
• The function 'covers' is never used.
• The function 'install' is never used.
• The function 'uninstall' is never used.
• The function 'loaded' is never used.
• The function 'hasClassNames' is never used.
• The function 'hasCompilerStructs' is never used.
• The function 'body' is never used.
• The function 'fromHandle' is never used.
• The function 'fromMethodID' is never used.
• The function 'inJava' is never used.
• The function 'compiledMethod' is never used.

[jbachorik]

HI @bric3 - you picked the right approach with the counters.
But it will be better if you have only one counter for the whole unwinding - keeping track of each unwound frame type would be too expensive.