ark_runtime_core/docs/memory-management-SW-requirements.md

Introduction

The main components of Panda memory management:

• Allocators
• Garbage Collector (GC)

Allocators have two purposes:

1. Allocations for the application
2. Allocations for the internal usage by Runtime (Allocations for compiler purposes, for GC internal structures etc)

Garbage Collector: GC automatically recycles memory that will never be used again. GC used to recycle memory allocated as result of application work (objects, compiled code etc).

Overall Description

Allocator

Allocator Types

• Bump pointer allocator
• Arena Allocator (objects can be deallocated at once (list of arenas, almost at once - O (number of arenas in the list)))
• Freelist allocator
• TLAB
• Run of slots allocator
• Code allocator

Spaces

• Code space (executable)
• Compiler Internal Space (linked list of arenas)
• Internal memory space for non-compiler part of runtime (including GC internals)
• Object space
• Non-moving space (space for non-movable objects)

GC

• Concurrent generational GC (optional - we can disable generational mode)
• GC for classes (optional)
• GC for code cache (optional)
• Reference processor

High level requirements for GC:

• Acceptable latency (max pause) for good user experience
• Acceptable throughput
• Acceptable footprint size

Key Features of the Memory Management System

You can flexibly configure the set of allocators and GCs. You can choose MM configurations for applications using a profile (for example, you can choose non-compacting GCs with freelist allocators for some applications if acceptable metrics is available for the applications).

Interaction with Other Components

Allocator

• Allocator API for runtime
• TLAB API for compiler and interpreter
• Interfaces for tools

GC

• Safepoints
• Reference storage and additional interfaces for MM <-> JNI interaction
• Barriers APIs for compilers and interpreters
• Possibility to change VRegs for any frame in the stack
• Interfaces for tools

Additional Requirements

• Memory management flexible enough to work with multiple languages.
• Provide various statistics data