Shulou(Shulou.com)06/01 Report--

In this article, the editor introduces in detail "what are the differences between Linux processes and threads", with detailed contents, clear steps and proper handling of details. I hope that this article "what are the differences between Linux processes and threads" can help you solve your doubts.

The first choice is to have a certain perceptual understanding of concurrency before understanding the concept of process and thread. if the server can only serve one client at the same time, and other clients wait there, it can be seen that its poor performance will be scolded by customers, so concurrent programming arises at the historic moment, and concurrency is a problem that must be considered in network programming. There are many ways to achieve concurrency: for example, multi-process, multi-thread, IO multiplexing.

Multiple processes

A process is the basic unit of resource allocation (CPU, memory, etc.), and it is an instance of program execution. When the program is running, the system will create a process, allocate resources to it, and then put the process into the process ready queue. When the process scheduler selects it, it will allocate CPU time to it, and the program will actually run.

The Linux system function fork () can create a child process in the parent process, so that when a process receives a new request from the client, it can copy a child process for processing, the parent process is only responsible for monitoring the arrival of the request, and then create a child process to process it, so that concurrent processing can be achieved.

#-*-coding:utf-8-*-import osprint ('current process:% s startup....'% os.getpid ()) pid = os.fork () if pid = 0: print ('child process:% s, parent process is:% s'% (os.getpid (), os.getppid ()) else: print ('process:% s created child process:% s (os.getpid (), pid)

Output result:

Current process: 27223 starting. Process: 27223 created child process: 27224 child process: 27224, parent process: 27223

The fork function will return the result twice, because the operating system will copy the data of the current process once, and then the program will continue to run the following code in two processes. Fork is returned in the parent process and the child process. The value pid returned in the child process is always 0. In the parent process, the process id of the child process is returned.

Multithreading

Thread is the smallest unit of program execution, it is an execution flow of process and the basic unit of CPU scheduling and dispatching. A process can be composed of many threads, and all resources of the process are shared among threads, and each thread has its own stack and local variables. Threads are independently scheduled and executed by CPU, which allows multiple threads to run at the same time in a multi-CPU environment. Similarly, multithreading can also implement concurrent operations, allocating one thread for each request.

What are the differences and advantages and disadvantages between threads and processes?

The process is the smallest unit of resource allocation, and the thread is the smallest unit of program execution.

A process has its own independent address space, and each time a process is started, the system allocates address space for it and sets up a data table to maintain code, stack and data segments, which is very expensive. Threads share data in a process and use the same address space, so it is much less expensive for CPU to switch a thread than a process, and it is much less expensive to create a thread than a process.

The communication between threads is more convenient. Threads under the same process share global variables, static variables and other data, while the communication between processes needs to be carried out by means of communication (IPC). However, how to deal with synchronization and mutual exclusion is the difficulty of writing multithreaded programs.

But multiprocess programs are more robust. In multithreaded programs, as long as one thread dies, the whole process dies, and the death of one process does not affect the other, because the process has its own independent address space.

After reading this, the article "what are the differences between Linux processes and threads" has been introduced. If you want to master the knowledge points of this article, you still need to practice and use it yourself to understand it. If you want to know more about related articles, welcome to follow the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.