AGENTS

Name: Daemon Purpose: Daemon is a background daemon thread module for the ArkTS runtime (ecmascript). It provides asynchronous execution of Garbage Collection (GC) related tasks with features including:

• Concurrent marking for CMC (Concurrent Mark-Compact) garbage collector
• Asynchronous garbage collection execution
• Unified GC marking support
• Task grouping mechanism to prevent duplicate task submission
• Singleton pattern for thread lifecycle management
• QoS (Quality of Service) priority adjustment support
• Thread-safe task queue with mutex and condition variable synchronization Primary Language: C++

Directory Structure

daemon/
├── daemon_task.h                                              # Base DaemonTask class and task type definitions
├── daemon_task-inl.h                                          # Inline implementations for concrete task types (templates)
├── daemon_thread.h                                            # DaemonThread class definition
└── daemon_thread.cpp                                          # DaemonThread implementation

Building

The daemon module is built as part of the ArkCompiler module in the GN build system. There is no independent BUILD.gn file in the daemon directory. The source files are included in the main ecmascript BUILD.gn configuration:

# Build for OHOS ARM64
./build.sh --product-name rk3568 --gn-args use_musl=true --target-cpu arm64 --build-target ark_js_packages

# Build for OHOS ARM32
./build.sh --product-name rk3568 --build-target ark_js_packages

# Debug build (add to any command)
--gn-args is_debug=true

Test Suite

The daemon module has comprehensive unit tests located in the ecmascript/tests directory:

# Build and generate an executable file
./build.sh --product-name rk3568 --build-target GC_Daemon_Test
# Send the executable file to the device using hdc
hdc shell send ./out/rk3568/tests/unittest/ets_runtime/GC_Daemon_Test /data/local/tmp/
# Run the executable file
hdc shell
cd /data/local/tmp/
chmod 777 ./GC_Daemon_Test
./GC_Daemon_Test

Test coverage includes:

• Task posting and execution (PostTaskWithDaemon, PostTaskTwiceWithDaemon)
• Duplicate task prevention across task groups
• Multi-threaded task submission scenarios
• Daemon thread lifecycle management (pre-fork/post-fork scenarios)
• Mock task implementations for testing

Dependency

Package Dependencies

Dependency	Purpose
common_components/taskpool	TaskPool integration (runner.h, taskpool.h)
ecmascript/js_thread	Base JSThread class for thread management
ecmascript/mem/heap	Heap memory management interface
ecmascript/mem/shared_heap	SharedHeap for concurrent GC operations
ecmascript/mutator_lock	MutatorLock for thread synchronization
ecmascript/platform/mutex	Mutex and ConditionVariable primitives
ecmascript/runtime	Runtime lifecycle management
qos (optional)	Quality of Service priority management

External Directory Interactions

• ../mem/ - Memory management subsystem (Heap, SharedHeap)
• ../mem/shared_heap/ - Shared heap implementation for concurrent marking
• ../platform/ - Platform-specific synchronization primitives
• ../../common_components/taskpool/ - Shared TaskPool component for concurrent task execution
• ../runtime.cpp - Runtime startup/shutdown integration

Component Lifecycle Integration

The DaemonThread is created and destroyed by the Runtime:

• Creation: Runtime::PreCreateVm() calls DaemonThread::CreateNewInstance()
• Destruction: Runtime::DestroyIfLastVm() calls DaemonThread::DestroyInstance()

Boundaries

Allowed Operations

• ✅ Add new daemon task types by extending the DaemonTask base class
• ✅ Implement new GC-related tasks by creating template specializations
• ✅ Modify task scheduling algorithms within DaemonThread::Run()
• ✅ Extend task group categories for new task types
• ✅ Add new QoS priority levels or scheduling policies
• ✅ Extend synchronization mechanisms for thread safety

Prohibited Operations

• ❌ Do NOT directly modify the singleton instance (instance_) - use provided static methods
• ❌ Do NOT bypass the task grouping mechanism (postedGroups_, runningGroup_)
• ❌ Do NOT post tasks without checking daemon thread running state
• ❌ Do NOT modify SharedMarkStatus from non-daemon threads without proper synchronization
• ❌ Do NOT call FinishRunningTask() from outside the daemon thread context
• ❌ Do NOT destroy the daemon thread while tasks are still pending
• ❌ Do NOT use raw thread creation - always use the DaemonThread abstraction