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.
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Sign up to join this communityCan 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.
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) or kpti=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.
SRBDS - Special Register Buffer Data Sampling
kernel.org/doc/html/latest/admin-guide/hw-vuln/…
Jan 24, 2021 at 9:39
With a kernel 5.1.13 or newer :
On boot parameter you can use
mitigations=off
With a kernel older than 5.1.13 :
noibrs noibpb nopti nospectre_v2 nospectre_v1 l1tf=off nospec_store_bypass_disable no_stf_barrier mds=off mitigations=off
Add either mitigations=off
or that long one-liner to your /etc/sysconfig/grub
and re-generate grub's configuration file with
grub2-mkconfig
(your distributions procedure will vary).
Debian/Ubuntu derived distributions:
Edit the file /etc/default/grub
then run
update-grub
grub-install /dev/sdX
after update-grub
! Just reboot.
Apr 28, 2020 at 15:47
mitigations=off
in that long one-liner. Is that going to do anything on older kernels?
The proper steps on Ubuntu:
edit /etc/default/grub
find the GRUB_CMDLINE_LINUX_DEFAULT
line:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash mitigations=off"
Add the mitigations=off
section (shown above, but missing from other posts)
then
sudo update-grub
then
sudo-grub-install /dev/sdX