Linux: How to disable mitigations for CPU vulnerabilities

[biodoc]

Use at you're own risk.

https://blog.sleeplessbeastie.eu/2020/0 ... abilities/

[StefanR5R]

While I never profiled its effects, I have mitigations off on all of my DC-dedicated computers.
It was a small nuisance to figure out how to set the GRUB config accordingly in Mint.
In OpenSuse, there is a dialogue for this in their central system management GUI.

[biodoc]

I ran your llrDIV script on my 2P Ivy with mitigations on and off and although the trend seemed to be a slight improvement, I doubt it's statistically significant.
Mitigations on:


Mitigations off:

[biodoc]

It was a small nuisance to figure out how to set the GRUB config accordingly in Mint.

For others using Mint:

sudo nano /etc/default/grub

Before editing:

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=0
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

After editing:

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=0
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash mitigations=off"
GRUB_CMDLINE_LINUX=""

Save the change.
sudo update-grub
reboot

[crashtech]

I did not rtfm but I skimmed it, and didn't find how to put more than one command in that line. Some of my PCs have this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet vsyscall=emulate"

I'm not sure how to add that in, it looks like just put "mitigations=off" into the quotation marks...?

For instance:

GRUB_CMDLINE_LINUX_DEFAULT="quiet vsyscall=emulate mitigations=off"

[StefanR5R]

Correct. You can enter as many kernel parameters as you need, separated by space characters, and in any order.

Added in 4 minutes 32 seconds:

I ran your llrDIV script on my 2P Ivy with mitigations on and off and although the trend seemed to be a slight improvement, I doubt it's statistically significant.

Every percent counts. ;-)

Perhaps GPGPU workloads profit more, as they involve more calls into the kernel, and device I/O.

[crashtech]

Thanks for being patient with such elementary queries, Stefan. I don't think I can understate how valuable your advice has been over the years.

[crashtech]

Every percent counts. ;-

In drag racing they call this "stacking tenths," referring to arriving just a tenth of a second faster at the finish. One small change may not seem to make a difference, but many small changes do.

[biodoc]

I shut down the 2P Ivy beast for now. The PPD is between a 3700X and a 3900X and it draws 310 watts from the wall with turbo boost off. I'll replace it when you can actually buy hardware sometime in the future.

[Skillz]

Every percent counts. ;-

In drag racing they call this "stacking tenths," referring to arriving just a tenth of a second faster at the finish. One small change may not seem to make a difference, but many small changes do.

When in doubt, just put it on the bottle.

[crashtech]

We need nitrous for PCs!

[Skillz]

Remember the turbo button from the 90s?