For both applications, the RSS column would count the size of the shared library, even though it’s only been loaded once.

When you open the second application, it will avoid reloading a duplicate copy of the library into RAM, and just share the same copy that the first application is using. If you open one of the applications, the necessary library will be loaded into RAM. If you have two image editing programs on your Linux system, they likely utilize many of the same image processing libraries. However, shared libraries are counted for each process, making the reported amount of physical memory usage less accurate. At first glance, it may seem like the RSS number is the real amount of physical memory that a system process is using. This is the size of memory that a process has currently used to load all of its pages. The VSZ size is therefore not usually an accurate measurement of how much memory a process is using, but rather an indication of the maximum amount of memory a process can use if it loads all of its functions and libraries into physical memory. The VSZ size you see has taken all of these pages into consideration, but it doesn’t mean they’ve been loaded into physical memory. Linux utilizes demand paging, which only loads pages into memory once the application makes an attempt to use them. For example, many applications have functions to carry out certain tasks, but may not load them into memory until they are needed. This is the size of memory that Linux has given to a process, but it doesn’t necessarily mean that the process is using all of that memory. VSZ and RSS columns in the ps command output

Linux monitor ram usage