2020-08-29: process thread differences, in addition to the inclusion relationship, the underlying details?

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Fogo's answer 2020-08-29：

1. Fundamental difference
process ： The minimum unit of resource scheduling .
Threads ：CPU Scheduling minimum unit .

2. address space
process ： The process has its own address space , Every time a process is started , The system will allocate address space to it , Create data tables to maintain code snippets 、 Stack and data segments .
Threads ： Threads have no independent address space , Threads of the same process share the address space of this process .

3. Memory and files share
process ： When you create a process ,mm_struct It will point to another address , Use copy-on-write replicate .
Threads ： And when you create a thread ,mm_struct Will point to the same virtual memory area of the parent process , So there will be resource conflicts .

Regardless of thread and process , stay linux The creation in is very fast .

4. block
process ： Process control block PCB. A process uses ProcessControlBlock On the one entry Record its basic information （pid,state,priority etc. ）, The process will be allocated a logical memory address space by the operating system , That is, it has a memory space for use .
Threads ： Thread control block TCB. A thread is a unit within a process that is responsible for executing a task , This unit uses ThreadControlBlock On the one entry Record its basic information （tid,state,priority,counter,register info etc. ）, This unit has its own stack For mission execution .

5. overhead
process ： Process execution cost is high .
Threads ： Low thread execution cost .

6. Switching speed
process ： Switching is relatively slow .
Threads ： Switching is relatively fast .

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