Today i’ve decided to write some words about cache and caching, because i remembered some people that didn’t know how those work.
Good, i’ll do this using an analogy, as usual, because it’s important to understand how it works, and implement it yourself after your own imagination.
Let’s say that I, Piry, am a guy that writes cds. I have a little store and all kinds of computer games, which i can burn.
Someone comes to buy a pc game. I go to my computer, burn the disk and give it to him. That takes about 3 minutes.
Caching allows me to shorten that time. I’ll represent caching as a shelf, with cds.
For example when someone comes to buy the game, i make a cd, and as i give it to him, the computer makes another cd i put in the shelf.
When someone else comes, i first look in the shelf to see if the game he wants is there.
If it is, those 3 minutes turn into 10 seconds, if not … i’ll have to go burn it, but i waste a little more time (adding to the cache).
Now it depends if you really need caching, but overall the time is really shorter, so in most cases it’s worth it.
But there are more levels of caching …
A two level cache would mean i have that shelf at the entrance (level 1) and another one on the way to the computer (level 2) … which will force me too look in both shelves, but even if it were 5 of them, i’d still have a shorter time. That’s the idea of caching … a place in which certain information is kept for fast access.
That’s how a processor works (you saw the L1 and L2 cache levels), even the computer memory is considered to be a cache (because it shortens the hard-drive -> memory -> processor trip to memory -> processor(which is a lot faster then hard-drive -> memory)), even the speed-dial on your cell-phone can be considered a cache.
That’s about it, hope you understood how caching systems work.
–The Pirahna (aka Piry)
