Thread

• A thread is a path of execution within a process

• A thread is a basic unit of CPU utilization, consisting of a program counter, a stack, and a set of registers, (a thread ID).

• A thread is also called a lightweight process

• THreads are very useful in mordern programming whenever a prcess has multiple tasks to perform independently of the others.

• A process can contain multiple threads.

• This is when one of the tasks may block, annd it is desired to allow the other tasks to procees without blocking.

Benefits of multithreaded programming

REsource sharing: this quality is especially useful in designing user interfaces

Scalability:

Responsiveness

Economy

Multithreading Models

2 types: user threas and kernal threads

1. many to one model

• maps many yserr-level threads to one kerne thread.
• the entire process will blocke if a thread makes a blocking system call.
• beacuase only one thread can access the kenel at a time, multiple threads are ubable to run in parallel on multicore systems.

adv

• less overhead
• eady to manage

dis-adv

• if one is block all other thread is blocked

2. ONe to one model

• maps each user thread to kernel thread
• allows meltiple threads to run in parallel on multiprocessors
• only dreaback to this model is that creating a user thread requires creating the correstpoding kernell thread.

adv

• cuncurrency achieved

dis-adv

• more overhead

3. many to many model

• multiplexes many user-level threads to smaller or equal number of kernel threads.
• number of kernel threads may be specific to either a particular application or a particular machine.
• developers can create as many user threads as necessary
• when a thread perrdorms a blocking system call the kernel can schedule another thread for execution

adv

• Better concurrency