CST 334 - Operating Systems (Week 4)

This week, I decided to write about my knowledge on weekly journal earlier than usual. That is because of the excitement I found while trying to understand the Paging.

First of all, a recall of material from last week, Week 3. The physical memory in hardware that provide memory address for processes. And visual memory, one is used to make the physical memory looks larger using complex algorithms inside the Operating Systems. The reason we need the visual memory is because the process requires more memory than the physical memory can provide. However, the tradeoff for using the visual memory is the lost in performance. For example, those moment when you run an application, website or searching for something in a large data storage. At that time, your PC starts running slow, the response time becomes significant and noticeable. That is because the running process is eating all the available memory and the visual memory kicks in.

Now the next thing is what I found interesting for this week: the algorithms behind the visual memory. I will take Page Table and Translation Lookaside Buffer (TLB) as examples. With Page Table, the Operating Systems has a list of page tables, while each page table, representing for each process, has a list of page entries. I think of it like a book, where each page is a different knowledge on its own. And when we need to pick the required information, just like the System need to pick the right Page Table to load in, we simply go over and pick the right page. On the other hand, TLB is not on the Operating Systems, but inside every process, every page table. TLB's task is a cache, a short list of frequently, important page entries. Using the book comparison again, it's like we have bookmarks so that we can turn to those pages quickly.

I could have stop there, but my curiosity guided me to discover the connection between physical and visual memory with RAM and VRAM. All of the sudden, I realized people say, "not enough RAM". Now I understand that is the concept of physical switching to visual memory, affecting the performance as I mentioned. And then is fascinating to discover that due to advanced technology and complex algorithms, humanity manage to make larger RAM. 8 to 16 to 32 to 64, and it keeps growing. Those are actual numbers, that means they are stored physically (many switches for 0 and 1 in those RAM!). Unfortunately, I am not the hardware engineer to fully know how they manage to do so.

For the VRAM, it is the similar concept, but I discovered it through a game: Total War. While playing the game, there is an option that improves the Graphics at the cost of Memory and Performance. I wasn't sure back then, but now my mind is opened, and I know: it is the concept of switching from physical memory in VRAM to visual memory, consuming memory on disk and reducing performance in the process.