The following chart shows the impact on CPU usage after applying the Meltdown patch.
As you can see, the CPU usage has bumped 25-30%. We're going to need to upgrade our hardware this weekend. No outages expected.
If you're not aware of what Meltdown is - it's a serious hardware vulnerability that's been recently discovered and affects almost all moderns processors.
Let me try to explain this attack in a non-technical way... This is one of those "cache timing" attacks, where one process can easily tell whether some data belongs to another process by looking at the response timings. If the timing is fast, this means the data is coming from the processor cache, if it's slow - it means the processor has to go to RAM to get the data.
Someone at HackerNews has come up with a beautiful library analogy:
When someone returns a book to the library, the librarian keeps it on his desk for some time (before taking it to the back), right? So you (the attacker) come in to the library and ask for "Mody Dick". If the librarian gives you the book immediately (from his desk) this means someone has just returned the book. This way you can tell, "Person X has just read Moby Dick".