Operating System - CH4 Threads

Process creation is heavy-weight

Thread creation is light-weight

multi-thread優點

• responsiveness
• resource sharing
• economy
• scalability 同一個process內的不同thread可以平行在不同CPUs上執行

multicore programming challenge

• divide activities
• balance
• data splitting
• data dependency
• test and debugging

User Threads

Kernel Threads: kernel 知道每條thread

Thread cancellation

• asynchronous cancellation: terminate thread immediately
• deferred cancellation: allow the target thread 定期確認自己是否應該cancel

Thread libraries: provide programmer with API to creating and managing threads

Java thread 

• cread new class derive from Thread class
• define a class that implements the Runnable interface

Signal Handling: signals are used to notify a process that a particular event has occured

Signal handler is used to process signals.

Thread Pools: create a number of threads in a pool where they await work.

upcalls

• for many-to-many and two-level models
• 溝通機制 from the kernel to the thread library.
• allow app to maintain the correct number kernel threads.

clone() allow a child task to share the address space of the parent task.