Before or after turning off Hyper Threading and speculative execution on your Intel microprocessor?
(The point being that 5% slowdown is a drop in the bucket compared to what we've already lost due to Intel's chip design problems. AIUI, HT is a 15-20% slowdown, and SE was another 20% slowdown.)
But now you can in theory run your programs on <strange underused architecture> that doesn't suffer from those vulnerabilities thanks to the power of WASM.