CPU caches and page caches

- [Instructor] So caching is all about…saving some data or instructions in faster memory…than where it was, and that helps if…you're going to use it again later.…If you're not going to ever get back to it,…it doesn't save you anything to cache it.…So the principle that's valuable for caching…is called locality.…Technically, temporal and spatial locality.…Temporal locality is, you're referencing something…that you've recently referenced in time,…and spatial locality is you're referencing something…close by to something you referenced before.…

And when a program has good locality,…then cache tends to be effective.…Now, caches are really common in computer architectures,…and in the way the kernel works.…So there's multiple caches.…A typical modern CPU has several level of caches.…Sometimes they'll have separate caches…for instructions and data.…So how you organize your program instructions…and your program data can be optimized for best cache use.…And when it comes to file system, the disk,…the kernel caches disk blocks.…