A process is mainly an environment for executing user-level programs. The process allows the kernel to multitask, so that thousands of processes can be executed on an operating system. Each process has its own independent process PID and is unique. Process creation is created by the system call fork(), fork() creates a copy of its own process with its own process number, and then calls the system call exec() to start executing different programs. The following shows the process creation process of executing commands in the shell, as shown in the following figure:
According to the above figure, we can get that the system call fork() can achieve Copy-On-Write, which is the COW strategy to improve performance. This adds a reference to the original address space instead of copying all content, but once any process is to be Modify, then an independent copy of the modification will be created at this time. The following shows the complete life cycle of the process, specifically:
On-proc refers to the process running on the CPU, and ready-to-run refers to the process can run, but still waiting for the CPU to allocate resources in the CPU run queue. I/O blocking, let the process enter the sleep state until the I/O completes the process is awakened. The zombie state occurs when the process terminates. At this time, the child process state waits for its parent process to read, or until it is cleared by the kernel. Such a scheduling process can be simplified to the following process, specifically as follows:
Software testing is the easiest subject in IT-related industries to get started~ It does not require the logical thinking of developers, and operations and maintenance personnel are not required to be on call 24 hours a day. What is needed is a careful attitude and a broad understanding of IT-related knowledge. The growth path of each tester from entering the industry to becoming a professional expert can be divided into three stages: software testing, automated testing, and test development engineers.
Here are some information I have compiled. If you don’t want to experience the self-study again, you can’t find the information, no one answers the question, and you feel like giving up after a few days, you can add our software testing exchange group 313782132, which contains various software Test data and technical exchange