Unshrouding Turin (or Benvenuto a Torino)

1404.503 - 1430.416 Adam Leventhal

Skylake is what did that. But you also had this problem on Broadwell with AVX2 and the others. And it's actually worse than just running an instruction. If you actually just leave the AVX save state bit such that Intel thinks it's modified in the register state, that's enough to trigger this slowdown sometimes. Oh, man. You might not remember this. We had a nasty bug back at Joyent.