D-OS-Ch03-Threads

Threads

Thread Concept

• D-SP-Ch11aa-Process_and_Thread
• D-SP-Ch11ab-Thread_Benefit_and_Drawback
• Data Parallelism vs. Task Parallelism
• TCB

Concurrent Programming

• Single Process on Single Processor
• Multiple Processes on Single Processor
• Single Instruction Single Data
• Multiple Instruction Multiple Data
• Single Instruction Multiple Data (SIMD)
• Zero Instruction Multiple Data (MIMD)

Speedup

Amdahl’s Law

• Amdahl’s Law

$$\text{speedup}=\frac{1}{s+\frac{1-s}{p}}$$

• where $s$ is serial portion, $p$ is number of cores

Gustafson’s law

$$\text{speedup}=\frac{\text{single core time}}{\text{multicore time}}=\frac{s+p(1-s)}{1}=s+p(1-s)$$

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Threading Model

User Level Thread (ULT)

user-level thread

Kernel Level Thread (KLT)

kernel-level thread

Multithreading Model

• many-to-one: ULT
• one-to-one: KLT
• many-to-many (N:M): Hybrid
• two level: similar to N:M, but allow user to bound user thread to kernel thread (for latency sensitive thread)

Synchronous vs. Asynchronous Threading

Asynchronous Threading

D-OS-Ch03e-Asynchronous_Threading

Synchronous Threading

D-OS-Ch03f-Synchronous_Threading

Implicit Threading

Implicit Threading vs. Explicit Threading

• Implicit Threading: 將 thread 的建立、管理、銷毀都交給 compiler 決定，程式設計者只需要指出哪裡可以平行便可以 (e.g., OpenMP)
• Explicit Threading: 由程式設計師自己管理 thread 週期 (e.g., pthread)

Thread Pool

D-OS-Ch03a-Thread_Pool

Worker Thread

D-OS-Ch03b-Worker_Thread

Thread Issues

fork() and exec() in Threads

threads vs. fork()

Signal Handling, Thread Cancellation

• thread signal
• cancelling threads

Thread-Local Storage (TLS)

D-OS-Ch03c-TLS

Scheduler Activation

D-OS-Ch03d-Scheduler_Activation