Xiaopopular -- physical memory, page files, swap areas, and virtual memory

Today, we can see the road to cloud computing in the blog Park.ArticleReprinted.

Physical memory, as its name implies, is the space provided by the memory stick on your computer's motherboard.

Page file, which is a space on the hard disk and is displayed as a file in windows. The meaning of this page file is that after the physical memory is fully occupied, the physical memory is moved to the space on the hard disk to free up the physical memory for the required applications.Program.

Swap zone, which is the sum of physical memory and page file space, data transmission and temporary storage between hard disk files, CPU and other IO (this sentence should be understandable to those who understand the basic process of computer operation ).

The concept of virtual memory is probably the most ambiguous so far, and has many different meanings. Here, I will first talk about the virtual memory in the eyes of a programmer.

Obviously, the Computer Configurations in this world are varied, and the number of available physical memory is also divided into many levels. As a tough programmer, we cannot consider how much memory the customer's machine can use when considering the program logic, it is also impossible to investigate in detail the actual physical memory address, but the OS will do this for us. Every running process will obtain a 4 GB memory address space, which is called virtual memory. All the addresses here are virtual and are not directly linked to the physical memory. On the other end of the operating system, the actual addresses mapped to these virtual addresses can be physical memory addresses or page file addresses. If the physical memory is smaller than the range of the virtual address, the mapped physical memory may also be a duplicate physical memory address segment. When using the address segment, you can clear the memory data, write the memory data to the page file to reuse the physical memory to improve the utilization efficiency of the physical memory.

Many people, especially those who are familiar with windows, often refer to page files as virtual memory. This is also Microsoft's opinion. They wrote this in their own operating systems. For details, see:

In aida64, or Everest, the virtual memory is a swap zone. Honestly, I don't understand what this concept is.

In fact, there is no problem with the above virtual memory statement. It is a conventional statement. The key is to know when the "virtual memory" refers to something, and the concept is not obfuscated.

By the way, I found that the memory scheduling of win7 is very strange. Physical memory is not released while being occupied. It is always released when the usage is very high (close to full, that is, write the page file. The hard drive performance of my laptop is not so good, so it will be stuck for half a day, and if the software is downloaded for a long time, it is easy to fill up the physical memory. It is said that this superfetch (spelling error ?) The effect, after the off, the memory usage is indeed a little slow, but the usage is still high, it looks really uncomfortable.

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