Process and thread relationships and differences _ go

1. Definition

A process is a program with a certain independent function about a single run activity on a data set, a process that is an independent unit of the system's resource allocation and scheduling .

A thread is an entity of a process that is the basic unit of CPU dispatch and Dispatch, which is a smaller unit that can run independently than a process. The thread itself basically does not own the system resources, only has a point in the operation of the necessary resources (such as program counters, a set of registers and stacks) , but it can share all of the resources owned by the process with other threads that belong to one process.

2. Relationship

One thread can create and revoke another thread, and can execute concurrently between multiple threads in the same process.

Relative to a process, a thread is a concept that is closer to the execution body, it can share data with other threads in the process, but has its own stack space and has a separate execution sequence.

3. Differences

The main difference between processes and threads is that they are different ways to manage operating system resources. The process has a separate address space, and after a process crashes, it does not affect other processes in protected mode, and the thread is just a different execution path in a process. Thread has its own stack and local variables, but there is no separate address space between the threads, a thread dead is equal to the entire process dead, so the multi-process program is more robust than multithreaded programs, but in the process of switching, the cost of large resources, efficiency is worse. but for some concurrent operations that require simultaneous and shared variables, only threads can be used, and processes cannot be used.

1) In short, a program has at least one process, and a process has at least one thread.

2) The thread partition scale is smaller than the process, which makes the multi-thread procedure high concurrency.

3) In addition, the process has a separate memory unit during execution, while multiple threads share memory, which greatly improves the efficiency of the program operation.

4) threads are still different from the process in the execution process. Each separate thread has a program run entry, sequence of sequence execution, and exit of the program. However, threads cannot be executed independently, and must be dependent on the application, which provides multiple threads of execution control.

5) from a logical point of view, the meaning of multithreading is that in an application, there are multiple execution parts that can be executed concurrently. However, the operating system does not consider multiple threads as separate applications to implement scheduling and management of processes and resource allocation. This is the important difference between processes and threads.

4. Pros and cons

Threads and processes have advantages and disadvantages in use: the overhead of thread execution is small but not conducive to the management and protection of resources, while the process is the opposite. At the same time, threads are suitable for running on SMP machines, while processes can be migrated across machines.

Ext.: http://blog.csdn.net/yaosiming2011/article/details/44280797

Process and thread relationships and differences _ go