Can I disable Spectre and Meltdown mitigation features in Ubuntu 18.04LTS?
I want to test how much more performance I gain when I disable these two features in Linux, and if the performance is big, to make it permanently.
performancevulnerability
Can I disable Spectre and Meltdown mitigation features in Ubuntu 18.04LTS?
I want to test how much more performance I gain when I disable these two features in Linux, and if the performance is big, to make it permanently.
Best Answer
A number of kernel boot parameters are available to disable or fine-tune hardware vulnerability mitigations:
nospectre_v1
(x86, PowerPC),nospectre_v2
(x86, PowerPC, S/390, ARM64),spectre_v2_user=off
(x86)spec_store_bypass_disable=off
(x86, PowerPC),ssbd=force-off
(ARM64)l1tf=off
(x86)mds=off
(x86)tsx_async_abort=off
nx_huge_pages=off
nopti
(x86, PowerPC) orkpti=0
(ARM64)tsx_async_abort=off
(x86)kvm.nx_huge_pages=off
(x86)A meta-parameter,
mitigations
, was introduced in 5.2 and back-ported to 5.1.2, 5.0.16, and 4.19.43 (and perhaps others). It can be used to control all mitigations, on all architectures, as follows:mitigations=off
will disable all optional CPU mitigations;mitigations=auto
(the default setting) will mitigate all known CPU vulnerabilities, but leave SMT enabled (if it is already);mitigations=auto,nosmt
will mitigate all known CPU vulnerabilities and disable SMT if appropriate.Some of these can be toggled at runtime; see the linked documentation for details.