Read the article...
I've seen several "before and after" benchmarks for Linux and Windows.
Several processors from Intel, and AMD were tested.
Meltdown usually resulted in performance losses, which varied by task.
Spectre had performance losses, but not to the degree of Meltdown.
(both were mostly I/O task, but some other task as well.)
Except for the FX8350, which after a Spectre patch ( I forget which atm), was actually faster on several task...
Maybe this is the next performance boost for my PC.
This is the list of a search with the word "spectre".
https://www.phoronix.com/scan.php?page=search&q=spectre
I'll see if I can dig up the benchmarks.
Barracuda