TPL(Task Parallel Library)에 대한 소개입니다. 데모 코드 - Multi Threading https://github.com/gyuwon/DotNetPractice/blob/master/Tasks/MultiThreading/Program.cs - Shard Resource Access https://github.com/gyuwon/DotNetPractice/blob/master/Tasks/SharedResourceAccess/Program.cs - Continuation https://github.com/gyuwon/DotNetPractice/blob/master/Tasks/Chapters/Program.cs - Parallelism Performance https://github.com/gyuwon/DotNetPractice/blob/master/Tasks/ParallelismPerformance/Program.cs - foreach vs. ForAll https://github.com/gyuwon/DotNetPractice/blob/master/Tasks/ForAll/Program.cs

1. TPL(Task Parallel Library)
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2. Background

3. Thread
• 운영체제가 프로세서 자원(CPU Time)을 할당하는 기본 단위
• Multi Threading
• Parallel Processing
• UI & Background Tasks
• Shared Resource Access

4. DEMO
Multi Threading
Shared Resource Access

5. Thread Pool
• 큐에 입력되는 작업들을 작업자 스레드에 할당해 처리
• Recycling
Thread Pool
Thread
Thread
Thread
…
Work Item Queue

6. Future
• 아직 결정 여부가 확실하지 않은 값에 대한 계산 작업 및 노출
• Future가 생성될 때 값은 결정되어 있거나 결정되어 있지 않음
• 값이 반환되는 시점에는 값이 결정되어 있음
• Promise

7. Tasks

8. Task
• Task ≠ Thread
• Task is a ‘Work Item’ (IThreadPoolWorkItem)
• Future
• Awaitable
• Task Scheduler

9. Default Task Scheduler
Thread Pool
Worker Thread
Local Queue
Worker Thread
Local Queue
Global Queue
Task
Task
Task Task
Task
Task
Task Task
…
…
… …
LIFO LIFO
FIFO
Work Stealing

10. Start
protected internal override void QueueTask(Task task)
{
if ((task.Options & TaskCreationOptions.LongRunning) != 0)
{
Thread thread = new Thread(…);
thread.IsBackground = true;
thread.Start(task);
}
else
{
…
ThreadPool.UnsafeQueueCustomWorkItem(task, …);
}
}

11. FromAsync
internal static Task FromAsyncImpl(IAsyncResult asyncResult, …)
{
…
Task t = new Task(…);
if (asyncResult.IsCompleted)
{
t.InternalRunSynchronously(…);
}
else
{
ThreadPool.RegisterWaitForSingleObject(…);
}
…
}

12. Result
• TResult Task<TResult>.Result
• 작업이 완료된 상태이면 즉시 반환
• 작업이 완료되지 않은 상태이면 완료될 때까지 대기

13. Continuation
• Task 완료 후 실행 할 Task를 생성
• ContinueWith
• GetAwaiter

14. ContinueWith
internal void ContinueWithCore(Task continuationTask, ...)
{
…
if (!continuationTask.IsCompleted)
{
…
// Attempt to enqueue the continuation
bool continuationQueued = AddTaskContinuation(…);
// If the continuation was not queued (because the task completed),
then run it now.
if (!continuationQueued) continuation.Run(this, …);
}
}

15. DEMO
Continuation

16. PLINQ(Parallel Linq)

17. Data Parallelism
Sequential Parallel
Processor
Processor
Processor
…Processor

18. Parallel Query
Query
from e in query
where …
select …
Parallel Query
from e in query.AsParallel()
where …
select …

19. DEMO
Performance

20. foreach vs. ForAll
foreach ForAll
Proc A
Proc A
Proc A
…
Proc B
Proc A
Proc A
Proc A
…
Proc B
Proc B
Proc B
…

21. DEMO
foreach vs. ForAll