Micro-threading

Introduction

There are some situations where applications need to execute lots of asynchronous concurrent operations. OS-level threads could be used for this purpose, but an application can create only a limited count of threads. As for CPU utilization there is no significant performance gain if more threads are created than physical cores available on a CPU. In fact threads could be used for parallel processing on a multi-core CPU and for writing more readable code. OS-level threads should be mainly used for parallelism and better CPU utilization. If a programmer needs to write code which will be called asynchronously, then OS-level threads will be rather expensive in perspective of system resources.

CPU context switching methods

• Cooperative (use of explicit Yield call)
• Preemptive (periodic timer based)
• Combined

Objectives

• Unlimited number of instances (limited by available memory)
• Fast switching, creation, destruction
• Automatic thread pool management by physical CPU core count
• Ability to run in main loop only (without TThread instances)
• Provide own synchronization tools (Yield, Sleep, CriticalSection, Semaphore, Mutex, WaitForMultipleObjects, Queues, Synchronize, ...)
• Priority control
• Support for view list of all microthreads

Implementations

• MicroThreading - Lazarus package, functional yet not finished, not multi-platform, needs patching the Free Pascal
• STAX - Single Threaded Asynchronous EXecution framework (STAX for short) enables async/await style co-routines for Free Pascal

External links

• C# Yield implementation in Delphi
• Cool little Coroutines function (Much better version)
• Fibers(Windows)
• MeSDK Delphi coroutine implementation