OS resource management

One of the roles of the operating system is to manage system resources.

These system resources include:

• CPU time
• Memory (RAM)
• Storage (disk space)
• Network bandwidth
• Peripheral devices (like printers, USB devices, etc)
• And more…

The application software must ‘talk through’ the operating system, which makes sure that no application can hog all the resources, and that no application is trying to access memory or devices that it shouldn’t be allowed to.

Resource allocation

When a program requests more memory to be allocated to it, for example, it asks the operating system. The operating system checks if there is enough free memory, and if so, it allocates that memory to the program.

If there isn’t enough memory available, the operating system might use a technique called ‘swapping’ to free up some memory by moving some data from RAM (also known as ‘paging’ or ‘virtual memory’).

Process scheduling

By default, software can’t use multiple threads and cores of the CPU. The operating system manages the CPU time by scheduling which processes get to use which threads of the CPU - it does this by rapidly switching between processes, giving the illusion that multiple processes are running at the same time (this is called ‘time slicing’).

While most processors now have many cores, the operating system still might run multiple processes on the same core by time slicing, especially if there are more processes than there are cores (which there almost always are - try opening your system monitor/task manager to see how many processes are running on your computer right now!)

Most processes also only use a tiny fraction of a CPU thread, so won’t need an entire thread dedicated to them. A good operating system will realise this and schedule processes accordingly!

Also, some processes might be given higher priority than others, meaning they get more CPU time. The operating system manages this priority system to make sure that processes that need more of the CPU, get it.