Why does WDCP keep showing that memory is almost used up?

1. As shown in the figure: In the system information display on the WDCP homepage, you can see that memory usage is almost exhausted.

2. Enter Memory Management and check the actual memory usage. It also shows that memory is almost fully occupied.

3. Next, we click “Force Release Memory”, and you can see that memory has dropped a lot. This actually clears out some frequently accessed items that Linux has placed.

In Linux, it is often found that there is very little free memory, and it seems that all memory is occupied by the system. On the surface, it feels that memory is insufficient, but this is not actually the case. This is an excellent feature of Linux memory management and, in this respect, differs from Windows memory management. The main characteristic is: No matter how large the physical memory is, Linux fully utilizes it, reads hard disk data that has been called by some programs into memory, and uses the high-speed read/write characteristics of memory to improve the data access performance of the Linux system. Windows, however, allocates memory to applications only when memory is needed, and cannot make full use of large-capacity memory space. In other words, each time some physical memory is added, Linux can fully utilize it, bringing benefits from the hardware investment, while Windows only treats it as decoration, even if 8GB or more is added.

This feature of Linux mainly uses free physical memory to allocate a portion of space as cache and buffers, thereby improving data access performance.

Page cache (cache) is a major disk cache implemented by the Linux kernel. It is mainly used to reduce disk I/O operations. Specifically, by caching data from the disk into physical memory, it turns disk access into physical memory access.

The value of disk cache lies in two aspects: First, the speed of accessing a disk is far lower than the speed of accessing memory; therefore, accessing data from memory is faster than accessing it from disk. Second, once data is accessed, it is very likely to be accessed again in the short term.

Therefore, after being used for a period of time, the Linux system will show that memory is almost full. In fact, the Linux system adds some frequently used things to the memory pool for quick access, thereby improving operating efficiency; it does not mean a real shortage of memory. If the Linux system's apache or mysql runs abnormally, freezes, or the server cannot be connected remotely, or processes cannot end or start normally, and at the same time memory is also shown as fully occupied, then it may indeed be that memory is exhausted and you need to consider adding memory.