Thread filter optim

[r1viollet]

What does this PR do?:

• Reserve padded slots
• Introduce a register / unregister to retrieve slots
• manage a free list

Motivation:

Improve throughput of applications that run on many threads with many context updates.

Additional Notes:

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: [JIRA-XXXX]

Unsure? Have a question? Request a review!

[github-actions]

🔧 Report generated by pr-comment-cppcheck

CppCheck Report

Errors (2)

• There is an unknown macro here somewhere. Configuration is required. If LP64_ONLY is a macro then please configure it.
• syntax error

Warnings (8)

• The class 'RecordingBuffer' defines member function with name 'flushIfNeeded' also defined in its parent class 'Buffer'.
• Member variable 'CodeCache::_image_base' is not initialized in the copy constructor.
• Member variable 'CodeCache::_image_base' is not assigned a value in 'CodeCache::operator='.
• Member variable 'JitWriteProtection::_restore' is not initialized in the constructor.
• Member variable 'JitWriteProtection::_restore' is not initialized in the constructor.
• Either the condition 'uc!=nullptr' is redundant or there is possible null pointer dereference: uc.
• Obsolete function 'alloca' called.
• Member variable 'ElfParser::_vaddr_diff' is not initialized in the constructor.

Style Violations (306)

• Class 'Arguments' has a constructor with 1 argument that is not explicit.
• 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.
• The class 'NativeFunc' does not declare a constructor although it has private member variables which likely require initialization.
• Local variable 'count' shadows outer function
• Local variable 'blob' shadows outer function
• Local variable 'i' shadows outer variable
• Parameter 'prefixes' can be declared as reference to const
• Variable 'cb1' can be declared as pointer to const
• Variable 'cb2' can be declared as pointer 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 '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.
• 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 '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 'CTimer::_cstack' is never used.
• class member 'CTimer::_signal' is never used.
• class member 'CTimer::_max_timers' is never used.
• class member 'CTimer::_timers' is never used.
• 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.
• Operator '|' with one operand equal to zero is redundant.
• 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
• struct member 'FrameDesc::fp_off' is never used.
• struct member 'FrameDesc::pc_off' 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::_data_align' is never used.
• Class 'WallClockEpochEvent' has a constructor with 1 argument that is not explicit.
• class member 'LockEvent::_address' is never used.
• class member 'LockEvent::_timeout' 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.
• 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 'Element' has a constructor with 1 argument that is not explicit.
• Class 'NoField' 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.
• 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.
• 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 'CollectedHeapWrapper' does not declare a constructor although it has private member variables which likely require initialization.
• class member 'VirtualSpaceSummary::_committed_end' is never used.
• class member 'GCHeapSummary::vptr' is never used.
• class member 'CollectedHeapWrapper::vptr' is never used.
• class member 'CollectedHeapWrapper::_gc_heap_log' is never used.
• class member 'CollectedHeapWrapper::_capacity_at_last_gc' is never used.
• class member 'CollectedHeapWrapper::_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.
• Class 'SpinLock' has a constructor with 1 argument that is not explicit.
• struct member 'TrackingEntry::skipped' 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.
• class member 'Log::_file' is never used.
• class member 'Log::LEVEL_NAME' 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.
• 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.
• class member 'ObjectSampler::CONFIG_UPDATE_CHECK_PERIOD_SECS' 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.
• Variable 'entry' can be declared as pointer to const
• 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
• 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 '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 'name' 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 'PerfEvents::_max_events' is never used.
• class member 'PerfEvents::_events' is never used.
• class member 'PerfEvents::_event_type' is never used.
• class member 'PerfEvents::_ring' is never used.
• class member 'PerfEvents::_cstack' is never used.
• class member 'PerfEvents::_use_mmap_page' is never used.
• Class 'ReservoirSampler' has a constructor with 1 argument that is not explicit.
• Class 'UnloadProtection' has a constructor with 1 argument that is not explicit.
• class member 'Symbols::_libs_limit_reported' is never used.
• class member 'UnloadProtection::_lib_handle' is never used.
• 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
• Parameter 'info' can be declared as pointer to const
• struct member 'RootSymbolEntry::name' is never used.
• struct member 'RootSymbolEntry::kind' is never used.
• class member 'ElfParser::_root_symbols' is never used.
• Class 'ExclusiveLock' has a constructor with 1 argument that is not explicit.
• Class 'SharedLock' has a constructor with 1 argument that is not explicit.
• Same expression on both sides of '-'.
• Local variable 'count' shadows outer function
• Parameter 'failures' can be declared as reference to const
• class member 'ProfiledThread::_buffer_size' is never used.
• class member 'ProfiledThread::_buffer' is never used.
• Variable 'existing' can be declared as pointer to const
• Variable 'chunk' can be declared as pointer to const
• class member 'ThreadFilter::kChunkShift' is never used.
• class member 'ThreadFilter::kChunkMask' is never used.
• class member 'ThreadFilter::kFreeListSize' is never used.
• struct member 'Slot::padding' is never used.
• struct member 'ChunkStorage::slots' is never used.
• class member 'ThreadInfo::_thread_names' is never used.
• class member 'ThreadInfo::_thread_ids' is never used.
• Condition 'enabled()' is always false
• The function 'loadAcquire' is never used.
• The function 'message' is never used.
• The function 'hasOption' is never used.
• The function 'cpuSamplerInterval' is never used.
• The function 'acquired' is never used.
• The function 'offset' is never used.
• The function 'skip' is never used.
• The function 'put16' is never used.
• The function 'put64' is never used.
• The function 'putFloat' is never used.
• The function 'putVar64' is never used.
• The function 'findBlobByAddress' is never used.
• The function 'binarySearch' is never used.
• The function 'dump' is never used.
• The function 'findSymbolsByPrefix' is never used.
• The function 'findImport' is never used.
• The function 'patchImport' is never used.
• The function 'findFrameDesc' is never used.
• The function 'libIndex' is never used.
• The function 'isMarked' is never used.
• The function 'minAddress' is never used.
• The function 'contains' is never used.
• The function 'get' is never used.
• The function 'getPage' is never used.
• The function 'get_tag' is never used.
• The function 'getCounters' is never used.
• The function 'getCounter' is never used.
• The function 'describeCounters' is never used.
• The function 'units' is never used.
• The function 'check' is never used.
• The function 'start' is never used.
• The function 'supported' is never used.
• The function 'setSighandlerTid' is never used.
• The function 'bounded_lookup' is never used.
• The function 'stop' is never used.
• The function 'interval' is never used.
• The function 'registerThread' is never used.
• The function 'unregisterThread' is never used.
• The function 'enableEvents' is never used.
• The function 'updateCounter' is never used.
• The function 'hasChanged' is never used.
• The function 'updateNumSamplableThreads' is never used.
• The function 'updateNumSuccessfulSamples' is never used.
• The function 'updateNumFailedSamples' is never used.
• The function 'updateNumExitedThreads' is never used.
• The function 'updateNumPermissionDenied' is never used.
• The function 'endEpoch' is never used.
• The function 'clean' is never used.
• The function 'newEpoch' is never used.
• The function 'encode' is never used.
• The function 'decode' is never used.
• The function 'threadEntry' is never used.
• The function 'sampleIdleThreads' is never used.
• The function 'field' is never used.
• The function 'category' is never used.
• The function 'root' is never used.
• The function 'strings' is never used.
• The function 'jniExceptionCheck' is never used.
• The function 'is_readable_pointer' is never used.
• The function 'used' is never used.
• The function 'alloc' is never used.
• The function 'level' is never used.
• The function 'next' is never used.
• The function 'cputime' is never used.
• The function 'micros' is never used.
• The function 'processStartTime' is never used.
• The function 'sleep' is never used.
• The function 'ntoh64' is never used.
• The function 'threadId' is never used.
• The function 'schedPolicy' is never used.
• The function 'threadName' is never used.
• The function 'listThreads' is never used.
• The function 'isLinux' is never used.
• The function 'installSignalHandler' is never used.
• The function 'replaceSigsegvHandler' is never used.
• The function 'replaceSigbusHandler' is never used.
• The function 'sendSignalToThread' is never used.
• The function 'getCpuDescription' is never used.
• The function 'getProcessCpuTime' is never used.
• The function 'getTotalCpuTime' is never used.
• The function 'copyFile' is never used.
• The function 'truncateFile' is never used.
• The function 'fileSize' is never used.
• The function 'freePageCache' is never used.
• The function 'mallocArenaMax' is never used.
• The function 'walkKernel' is never used.
• The function 'resetBuffer' is never used.
• The function 'getEventName' is never used.
• The function 'compute' is never used.
• The function 'sample' is never used.
• The function 'reverse16' is never used.
• The function 'is_probably_rust_legacy' is never used.
• The function 'demangle' is never used.
• The function 'handle_safefetch' is never used.
• The function 'safeFetch32' is never used.
• The function 'safeFetch64' is never used.
• The function 'load32' is never used.
• The function 'tryLockShared' is never used.
• The function 'withinCurrentStack' is never used.
• The function 'restore' is never used.
• The function 'stackAt' is never used.
• The function 'clearParsingCaches' is never used.
• The function 'parseLibraries' is never used.
• The function 'isRootSymbol' is never used.
• The function 'forTid' is never used.
• The function 'inBuffer' is never used.
• The function 'tid' is never used.
• The function 'noteCPUSample' is never used.
• The function 'lookupWallclockCallTraceId' is never used.
• The function 'recordCallTraceId' is never used.
• The function 'enterCrashHandler' is never used.
• The function 'exitCrashHandler' is never used.
• The function 'resetCrashHandler' is never used.
• The function 'isDeepCrashHandler' is never used.
• The function 'unwindFailures' is never used.
• The function 'filterSlotId' is never used.
• The function 'setFilterSlotId' is never used.
• The function 'accept' is never used.
• The function 'getThreadId' is never used.
• The function 'clearAll' is never used.
• The function 'updateThreadName' is never used.
• The function 'reportCounters' is never used.
• The function 'convertJvmExecutionState' is never used.
• The function 'initialized' is never used.
• The function 'ticks' is never used.
• The function 'frequency' is never used.
• The function 'ticks_to_millis' is never used.
• The function 'record' is never used.
• The function 'forEach' is never used.
• The function 'countFailures' is never used.
• The function 'collectAndReset' is never used.

[github-actions]

🔧 Report generated by pr-comment-scanbuild

[r1viollet]

I have reasonable performance on most runs:

Benchmark                                                       (command)  (skipResults)  (workload)  Mode  Cnt    Score   Error  Units
ThreadFilterBenchmark.threadFilterStress01  cpu=100us,wall=100us,filter=1           true           0  avgt         0.039          us/op
ThreadFilterBenchmark.threadFilterStress01  cpu=100us,wall=100us,filter=1           true           7  avgt         0.041          us/op
ThreadFilterBenchmark.threadFilterStress01  cpu=100us,wall=100us,filter=1           true       70000  avgt       111.094          us/op
ThreadFilterBenchmark.threadFilterStress02  cpu=100us,wall=100us,filter=1           true           0  avgt         0.132          us/op
ThreadFilterBenchmark.threadFilterStress02  cpu=100us,wall=100us,filter=1           true           7  avgt         0.139          us/op
ThreadFilterBenchmark.threadFilterStress02  cpu=100us,wall=100us,filter=1           true       70000  avgt       108.666          us/op
ThreadFilterBenchmark.threadFilterStress04  cpu=100us,wall=100us,filter=1           true           0  avgt         0.258          us/op
ThreadFilterBenchmark.threadFilterStress04  cpu=100us,wall=100us,filter=1           true           7  avgt         0.278          us/op
ThreadFilterBenchmark.threadFilterStress04  cpu=100us,wall=100us,filter=1           true       70000  avgt       118.940          us/op
ThreadFilterBenchmark.threadFilterStress08  cpu=100us,wall=100us,filter=1           true           0  avgt         0.624          us/op
ThreadFilterBenchmark.threadFilterStress08  cpu=100us,wall=100us,filter=1           true           7  avgt         0.646          us/op
ThreadFilterBenchmark.threadFilterStress08  cpu=100us,wall=100us,filter=1           true       70000  avgt       160.170          us/op
ThreadFilterBenchmark.threadFilterStress16  cpu=100us,wall=100us,filter=1           true           0  avgt         1.780          us/op
ThreadFilterBenchmark.threadFilterStress16  cpu=100us,wall=100us,filter=1           true           7  avgt         2.288          us/op
ThreadFilterBenchmark.threadFilterStress16  cpu=100us,wall=100us,filter=1           true       70000  avgt       221.987          us/op

I'm not sure why some runs still blow up for higher numbers of threads.

[r1viollet]

CppCheck Report

Errors (2)

• There is an unknown macro here somewhere. Configuration is required. If LP64_ONLY is a macro then please configure it.
• syntax error

Warnings (8)

• The class 'RecordingBuffer' defines member function with name 'flushIfNeeded' also defined in its parent class 'Buffer'.
• Member variable 'CodeCache::_image_base' is not initialized in the copy constructor.
• Member variable 'CodeCache::_image_base' is not assigned a value in 'CodeCache::operator='.
• Member variable 'JitWriteProtection::_restore' is not initialized in the constructor.
• Member variable 'JitWriteProtection::_restore' is not initialized in the constructor.
• Either the condition 'uc!=nullptr' is redundant or there is possible null pointer dereference: uc.
• Obsolete function 'alloca' called.
• Member variable 'ElfParser::_vaddr_diff' is not initialized in the constructor.

Style Violations (306)

• Class 'Arguments' has a constructor with 1 argument that is not explicit.
• 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.
• The class 'NativeFunc' does not declare a constructor although it has private member variables which likely require initialization.
• Local variable 'count' shadows outer function
• Local variable 'blob' shadows outer function
• Local variable 'i' shadows outer variable
• Parameter 'prefixes' can be declared as reference to const
• Variable 'cb1' can be declared as pointer to const
• Variable 'cb2' can be declared as pointer 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 '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.
• 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 '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 'CTimer::_cstack' is never used.
• class member 'CTimer::_signal' is never used.
• class member 'CTimer::_max_timers' is never used.
• class member 'CTimer::_timers' is never used.
• 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.
• Operator '|' with one operand equal to zero is redundant.
• 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
• struct member 'FrameDesc::fp_off' is never used.
• struct member 'FrameDesc::pc_off' 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::_data_align' is never used.
• Class 'WallClockEpochEvent' has a constructor with 1 argument that is not explicit.
• class member 'LockEvent::_address' is never used.
• class member 'LockEvent::_timeout' 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.
• 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 'Element' has a constructor with 1 argument that is not explicit.
• Class 'NoField' 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.
• 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.
• 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 'CollectedHeapWrapper' does not declare a constructor although it has private member variables which likely require initialization.
• class member 'VirtualSpaceSummary::_committed_end' is never used.
• class member 'GCHeapSummary::vptr' is never used.
• class member 'CollectedHeapWrapper::vptr' is never used.
• class member 'CollectedHeapWrapper::_gc_heap_log' is never used.
• class member 'CollectedHeapWrapper::_capacity_at_last_gc' is never used.
• class member 'CollectedHeapWrapper::_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.
• Class 'SpinLock' has a constructor with 1 argument that is not explicit.
• struct member 'TrackingEntry::skipped' 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.
• class member 'Log::_file' is never used.
• class member 'Log::LEVEL_NAME' 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.
• 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.
• class member 'ObjectSampler::CONFIG_UPDATE_CHECK_PERIOD_SECS' 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.
• Variable 'entry' can be declared as pointer to const
• 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
• 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 '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 'name' 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 'PerfEvents::_max_events' is never used.
• class member 'PerfEvents::_events' is never used.
• class member 'PerfEvents::_event_type' is never used.
• class member 'PerfEvents::_ring' is never used.
• class member 'PerfEvents::_cstack' is never used.
• class member 'PerfEvents::_use_mmap_page' is never used.
• Class 'ReservoirSampler' has a constructor with 1 argument that is not explicit.
• Class 'UnloadProtection' has a constructor with 1 argument that is not explicit.
• class member 'Symbols::_libs_limit_reported' is never used.
• class member 'UnloadProtection::_lib_handle' is never used.
• 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
• Parameter 'info' can be declared as pointer to const
• struct member 'RootSymbolEntry::name' is never used.
• struct member 'RootSymbolEntry::kind' is never used.
• class member 'ElfParser::_root_symbols' is never used.
• Class 'ExclusiveLock' has a constructor with 1 argument that is not explicit.
• Class 'SharedLock' has a constructor with 1 argument that is not explicit.
• Same expression on both sides of '-'.
• Local variable 'count' shadows outer function
• Parameter 'failures' can be declared as reference to const
• class member 'ProfiledThread::_buffer_size' is never used.
• class member 'ProfiledThread::_buffer' is never used.
• Variable 'existing' can be declared as pointer to const
• Variable 'chunk' can be declared as pointer to const
• class member 'ThreadFilter::kChunkShift' is never used.
• class member 'ThreadFilter::kChunkMask' is never used.
• class member 'ThreadFilter::kFreeListSize' is never used.
• struct member 'Slot::padding' is never used.
• struct member 'ChunkStorage::slots' is never used.
• class member 'ThreadInfo::_thread_names' is never used.
• class member 'ThreadInfo::_thread_ids' is never used.
• Condition 'enabled()' is always false
• The function 'loadAcquire' is never used.
• The function 'message' is never used.
• The function 'hasOption' is never used.
• The function 'cpuSamplerInterval' is never used.
• The function 'acquired' is never used.
• The function 'offset' is never used.
• The function 'skip' is never used.
• The function 'put16' is never used.
• The function 'put64' is never used.
• The function 'putFloat' is never used.
• The function 'putVar64' is never used.
• The function 'findBlobByAddress' is never used.
• The function 'binarySearch' is never used.
• The function 'dump' is never used.
• The function 'findSymbolsByPrefix' is never used.
• The function 'findImport' is never used.
• The function 'patchImport' is never used.
• The function 'findFrameDesc' is never used.
• The function 'libIndex' is never used.
• The function 'isMarked' is never used.
• The function 'minAddress' is never used.
• The function 'contains' is never used.
• The function 'get' is never used.
• The function 'getPage' is never used.
• The function 'get_tag' is never used.
• The function 'getCounters' is never used.
• The function 'getCounter' is never used.
• The function 'describeCounters' is never used.
• The function 'units' is never used.
• The function 'check' is never used.
• The function 'start' is never used.
• The function 'supported' is never used.
• The function 'setSighandlerTid' is never used.
• The function 'bounded_lookup' is never used.
• The function 'stop' is never used.
• The function 'interval' is never used.
• The function 'registerThread' is never used.
• The function 'unregisterThread' is never used.
• The function 'enableEvents' is never used.
• The function 'updateCounter' is never used.
• The function 'hasChanged' is never used.
• The function 'updateNumSamplableThreads' is never used.
• The function 'updateNumSuccessfulSamples' is never used.
• The function 'updateNumFailedSamples' is never used.
• The function 'updateNumExitedThreads' is never used.
• The function 'updateNumPermissionDenied' is never used.
• The function 'endEpoch' is never used.
• The function 'clean' is never used.
• The function 'newEpoch' is never used.
• The function 'encode' is never used.
• The function 'decode' is never used.
• The function 'threadEntry' is never used.
• The function 'sampleIdleThreads' is never used.
• The function 'field' is never used.
• The function 'category' is never used.
• The function 'root' is never used.
• The function 'strings' is never used.
• The function 'jniExceptionCheck' is never used.
• The function 'is_readable_pointer' is never used.
• The function 'used' is never used.
• The function 'alloc' is never used.
• The function 'level' is never used.
• The function 'next' is never used.
• The function 'cputime' is never used.
• The function 'micros' is never used.
• The function 'processStartTime' is never used.
• The function 'sleep' is never used.
• The function 'ntoh64' is never used.
• The function 'threadId' is never used.
• The function 'schedPolicy' is never used.
• The function 'threadName' is never used.
• The function 'listThreads' is never used.
• The function 'isLinux' is never used.
• The function 'installSignalHandler' is never used.
• The function 'replaceSigsegvHandler' is never used.
• The function 'replaceSigbusHandler' is never used.
• The function 'sendSignalToThread' is never used.
• The function 'getCpuDescription' is never used.
• The function 'getProcessCpuTime' is never used.
• The function 'getTotalCpuTime' is never used.
• The function 'copyFile' is never used.
• The function 'truncateFile' is never used.
• The function 'fileSize' is never used.
• The function 'freePageCache' is never used.
• The function 'mallocArenaMax' is never used.
• The function 'walkKernel' is never used.
• The function 'resetBuffer' is never used.
• The function 'getEventName' is never used.
• The function 'compute' is never used.
• The function 'sample' is never used.
• The function 'reverse16' is never used.
• The function 'is_probably_rust_legacy' is never used.
• The function 'demangle' is never used.
• The function 'handle_safefetch' is never used.
• The function 'safeFetch32' is never used.
• The function 'safeFetch64' is never used.
• The function 'load32' is never used.
• The function 'tryLockShared' is never used.
• The function 'withinCurrentStack' is never used.
• The function 'restore' is never used.
• The function 'stackAt' is never used.
• The function 'clearParsingCaches' is never used.
• The function 'parseLibraries' is never used.
• The function 'isRootSymbol' is never used.
• The function 'forTid' is never used.
• The function 'inBuffer' is never used.
• The function 'tid' is never used.
• The function 'noteCPUSample' is never used.
• The function 'lookupWallclockCallTraceId' is never used.
• The function 'recordCallTraceId' is never used.
• The function 'enterCrashHandler' is never used.
• The function 'exitCrashHandler' is never used.
• The function 'resetCrashHandler' is never used.
• The function 'isDeepCrashHandler' is never used.
• The function 'unwindFailures' is never used.
• The function 'filterSlotId' is never used.
• The function 'setFilterSlotId' is never used.
• The function 'accept' is never used.
• The function 'getThreadId' is never used.
• The function 'clearAll' is never used.
• The function 'updateThreadName' is never used.
• The function 'reportCounters' is never used.
• The function 'convertJvmExecutionState' is never used.
• The function 'initialized' is never used.
• The function 'ticks' is never used.
• The function 'frequency' is never used.
• The function 'ticks_to_millis' is never used.
• The function 'record' is never used.
• The function 'forEach' is never used.
• The function 'countFailures' is never used.
• The function 'collectAndReset' is never used.

[jbachorik]

I did run some comparison of native memory usage with different thread filter implementations - data is in the notebook

TL;DR there is no observable increase in the native memory usage (the UNDEFINED category). Anyway, it would be useful to have an extra counter for the ThreadIDTable utilization.

[zhengyu123]

Not sure if it is important, but it can race unregisterThread, you may want to check return value of fetch_sub to determinate if it is really full.

[zhengyu123]

I don't quite understand, are index and chunk_idx 1-to-1 matched?

[zhengyu123]

I believe that initializing new_chunk can be done before compare_exchange_strong. Then you don't need initialized flag, which can result an awkward situation, e.g. you found chunk, but it is not initialized.