disable _all_ mitigations

  • become root
  • edit /etc/default/grub
  • add the options to GRUB_CMDLINE_LINUX_DEFAULT
  • run update-grub

pti=off spectre_v2=off l1tf=off nospec_store_bypass_disable no_stf_barrier

On Linux distributions like Ubuntu 18.10 and Clear Linux the mitigation costs were about ~18% while both RHEL 8 Beta and openSUSE 15.0 had a nearly 40% hit.

Tested with Skylake-X. Older architectures like Nehalem, Sandy Bridge, Ivy Bridge, Haswell and Broadwell could be impacted much more.
https://www.phoronix.com/scan.php?page=article&item=spec-melt-8way&num=1