5 ms·

mitigations=off

by jmakov 5y ago

mitigations=off

BeeOnRope 5y ago
This won't restore your performance in this case: the microcode changes the behavior of the zero store optimization without any action from the kernel. If you accept the new microcode, you get the new, slower behavior. Perhaps there is an MSR bit you can flip to set the behavior back to the old way, but none has emerged so far.
- johnisgood 5y ago
  Thankfully I do save all of the microcodes, so I can just use an early version by simply rebuilding the initramfs. I also hold that package back on Arch, so it does not get upgraded. Might want to look for them here: https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/releases https://github.com/intel/Intel-Linux-Processor-Microcode-Dat... As to how to actually use those files to get your "intel-ucode.img", just take a look at: https://archlinux.org/packages/extra/any/intel-ucode/ https://archlinux.org/packages/extra/any/intel-ucode/ For the "iucode_tool": https://gitlab.com/iucode-tool/iucode-tool/-/wikis/home https://gitlab.com/iucode-tool/iucode-tool/-/wikis/home The actual PKGBUILD for it on Arch Linux: https://github.com/archlinux/svntogit-packages/blob/packages/intel-ucode/trunk/PKGBUILD https://github.com/archlinux/svntogit-packages/blob/packages... --- cd Intel-Linux-Processor-Microcode-Data-Files-microcode-${pkgver/./} rm -f intel-ucode{,-with-caveats}/list mkdir -p kernel/x86/microcode iucode_tool --write-earlyfw=intel-ucode.img intel-ucode{,-with-caveats}/ The above gives you "intel-ucode.img". Copy it to "/boot/". Run "mkinitcpio -p linux" or the like.
georgyo 5y ago
This likely would not help here. It is blamed on the cpu's microcode, not the kernel's mitigations.
- gmueckl 5y ago
  If that's the case, the microcode update happens some time during the boot process. It isn't persistent. It's either in the firmware or the OS. If it's on Linux, you can disable the boot script that performs the microcode update or patch it to update an older microcode image and you're done.
  - taneliv 5y ago
    Is dis_ucode_ldr kernel command line option sufficient to disable updates?

mitigations=off

by jmakov 5y ago

mitigations=off

This won't restore your performance in this case: the microcode changes the behavior of the zero store optimization without any action from the kernel. If you accept the new microcode, you get the new, slower behavior. Perhaps there is an MSR bit you can flip to set the behavior back to the old way, but none has emerged so far.

johnisgood 5y ago
Thankfully I do save all of the microcodes, so I can just use an early version by simply rebuilding the initramfs. I also hold that package back on Arch, so it does not get upgraded. Might want to look for them here: https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/releases https://github.com/intel/Intel-Linux-Processor-Microcode-Dat... As to how to actually use those files to get your "intel-ucode.img", just take a look at: https://archlinux.org/packages/extra/any/intel-ucode/ https://archlinux.org/packages/extra/any/intel-ucode/ For the "iucode_tool": https://gitlab.com/iucode-tool/iucode-tool/-/wikis/home https://gitlab.com/iucode-tool/iucode-tool/-/wikis/home The actual PKGBUILD for it on Arch Linux: https://github.com/archlinux/svntogit-packages/blob/packages/intel-ucode/trunk/PKGBUILD https://github.com/archlinux/svntogit-packages/blob/packages... --- cd Intel-Linux-Processor-Microcode-Data-Files-microcode-${pkgver/./} rm -f intel-ucode{,-with-caveats}/list mkdir -p kernel/x86/microcode iucode_tool --write-earlyfw=intel-ucode.img intel-ucode{,-with-caveats}/ The above gives you "intel-ucode.img". Copy it to "/boot/". Run "mkinitcpio -p linux" or the like.

georgyo 5y ago

This likely would not help here. It is blamed on the cpu's microcode, not the kernel's mitigations.

gmueckl 5y ago
If that's the case, the microcode update happens some time during the boot process. It isn't persistent. It's either in the firmware or the OS. If it's on Linux, you can disable the boot script that performs the microcode update or patch it to update an older microcode image and you're done.
- taneliv 5y ago
  Is dis_ucode_ldr kernel command line option sufficient to disable updates?