caching, hardware & software applications, cache hits & misses, L1 L2 L3 caches

What is Caching?

Caching is a simple yet powerful idea used everywhere in computing to make things faster. It works by keeping a smaller, faster storage space (the cache) near where data or computations are needed, so you don’t have to keep going back to the slower, larger storage (like RAM, disk, or even the internet). The key idea is to store the most commonly or recently used data in the cache because there's a high chance you’ll need it again soon.

Intuitive Explanation

Think of your workspace:

1. Main Desk (Cache): This is your small but very accessible desk where you keep your most-used items like pens, a notebook, and your laptop.
2. Bookshelf (Main Memory): This is nearby but less convenient. You store things you need occasionally, like reference books or files.
3. Basement Storage (Disk/Network): This is even further away. You only go there for things you rarely use or forgot you had.

Caching is like making smart decisions about what to keep on your desk (the fastest memory) so you don’t have to keep reaching for the bookshelf or, worse, the basement.

How Caching Works

1. Access Request: When your program (or hardware) needs data, it first checks the cache.
2. Cache Hit: If the data is found in the cache, it's used immediately, saving the time of going to slower storage.
3. Cache Miss: If the data isn’t in the cache, it’s fetched from the slower storage and added to the cache (possibly evicting some older data to make room).

Why Caching Works

Caching works and is effective because of locality:

1. Temporal Locality: If you’ve used something recently, you’re likely to use it again soon. For example, opening the same file repeatedly during a project.