docs: add documentation on performance tuning

Thanks to various people who submitted this information over time, and
special thanks to @maxpain for IOMMU fix.

Fixes #9539

Signed-off-by: Andrey Smirnov <[email protected]>

website/content/v1.8/talos-guides/configuration/performance-tuning.md

@@ -0,0 +1,75 @@
+---
+title: "Performance Tuning"
+description: "In this guide, we'll describe various performance tuning knobs available."
+---
+
+Talos Linux tries to strike a balance between performance and security/efficiency.
+However, there are some performance tuning knobs available to adjust the system to your needs.
+With any performance tuning, it's essential to measure the impact of the changes and ensure they don't introduce security vulnerabilities.
+
+> Note: Most of the suggestions below apply to bare metal machines, but some of them might be useful for VMs as well.
+
+If you find more performance tuning knobs, please let us know by editing this document.
+
+## Kernel Parameters
+
+Talos Linux kernel parameters can be adjusted in the following ways:
+
+* temporary, one-time adjustments can be done via console access, and editing the kernel command line in the bootloader (doesn't work for Secure Boot enabled systems)
+* on initial install (when booting off ISO/PXE), `.machine.install.extraKernelArgs` can be used to set kernel parameters
+* after the initial install (or when booting off a disk image), `.machine.install.extraKernelArgs` changes require a no-op upgrade (e.g. to the same version of Talos) to take effect
+
+### CPU Scaling
+
+Talos Linux uses the `schedutil` [CPU scaling governor](https://docs.kernel.org/admin-guide/pm/cpufreq.html) by default, for maximum performance, you can switch to the `performance` governor:
+
+```text
+cpufreq.default_governor=performance
+```
+
+### Processor Sleep States
+
+Modern processors support various sleep states to save power, but they might introduce latency when transitioning back to the active state.
+
+#### AMD
+
+For maximum performance (and lower latency), use `active` mode of the [amd-pstate driver](https://docs.kernel.org/admin-guide/pm/amd-pstate.html):
+
+```text
+amd_pstate=active
+```
+
+#### Intel
+
+For maximum performance (and lower latency), disable the `intel_idle` driver:
+
+```text
+intel_idle.max_cstate=0
+```
+
+### Hardware Vulnerabilities
+
+Modern processors have various [security vulnerabilities](https://docs.kernel.org/admin-guide/hw-vuln/index.html) that require software/microcode mitigations.
+These mitigations might have a performance impact, and some of them can be disabled if you are willing to take the risk.
+
+First of all, ensure that Talos system extensions `amd-ucode` and `intel-ucode` are installed (and using latest version of Talos Linux).
+Linux kernel will load the microcode updates on early boot, and for some processors, it might reduce the performance impact of the mitigations.
+The availability of microcode updates depends on the processor model.
+
+The kernel command line argument `mitigations` can be used to disable all mitigations at once (not recommended from security point of view):
+
+```text
+mitigations=off
+```
+
+There is also a way to disable specific mitigations, see [Kernel documentation](https://docs.kernel.org/admin-guide/hw-vuln/index.html) for more details.
+
+### I/O
+
+For Talos Linux before version 1.8.2, the I/O performance can be improved by setting `iommu.strict=0`, for later versions this is a default setting.
+
+Performance can be further improved at some cost of security by bypassing the I/O memory management unit (IOMMU) for DMA:
+
+```text
+iommu.passthrough=1
+```

website/content/v1.9/talos-guides/configuration/performance-tuning.md

@@ -0,0 +1,75 @@
+---
+title: "Performance Tuning"
+description: "In this guide, we'll describe various performance tuning knobs available."
+---
+
+Talos Linux tries to strike a balance between performance and security/efficiency.
+However, there are some performance tuning knobs available to adjust the system to your needs.
+With any performance tuning, it's essential to measure the impact of the changes and ensure they don't introduce security vulnerabilities.
+
+> Note: Most of the suggestions below apply to bare metal machines, but some of them might be useful for VMs as well.
+
+If you find more performance tuning knobs, please let us know by editing this document.
+
+## Kernel Parameters
+
+Talos Linux kernel parameters can be adjusted in the following ways:
+
+* temporary, one-time adjustments can be done via console access, and editing the kernel command line in the bootloader (doesn't work for Secure Boot enabled systems)
+* on initial install (when booting off ISO/PXE), `.machine.install.extraKernelArgs` can be used to set kernel parameters
+* after the initial install (or when booting off a disk image), `.machine.install.extraKernelArgs` changes require a no-op upgrade (e.g. to the same version of Talos) to take effect
+
+### CPU Scaling
+
+Talos Linux uses the `schedutil` [CPU scaling governor](https://docs.kernel.org/admin-guide/pm/cpufreq.html) by default, for maximum performance, you can switch to the `performance` governor:
+
+```text
+cpufreq.default_governor=performance
+```
+
+### Processor Sleep States
+
+Modern processors support various sleep states to save power, but they might introduce latency when transitioning back to the active state.
+
+#### AMD
+
+For maximum performance (and lower latency), use `active` mode of the [amd-pstate driver](https://docs.kernel.org/admin-guide/pm/amd-pstate.html):
+
+```text
+amd_pstate=active
+```
+
+#### Intel
+
+For maximum performance (and lower latency), disable the `intel_idle` driver:
+
+```text
+intel_idle.max_cstate=0
+```
+
+### Hardware Vulnerabilities
+
+Modern processors have various [security vulnerabilities](https://docs.kernel.org/admin-guide/hw-vuln/index.html) that require software/microcode mitigations.
+These mitigations might have a performance impact, and some of them can be disabled if you are willing to take the risk.
+
+First of all, ensure that Talos system extensions `amd-ucode` and `intel-ucode` are installed (and using latest version of Talos Linux).
+Linux kernel will load the microcode updates on early boot, and for some processors, it might reduce the performance impact of the mitigations.
+The availability of microcode updates depends on the processor model.
+
+The kernel command line argument `mitigations` can be used to disable all mitigations at once (not recommended from security point of view):
+
+```text
+mitigations=off
+```
+
+There is also a way to disable specific mitigations, see [Kernel documentation](https://docs.kernel.org/admin-guide/hw-vuln/index.html) for more details.
+
+### I/O
+
+For Talos Linux before version 1.8.2, the I/O performance can be improved by setting `iommu.strict=0`, for later versions this is a default setting.
+
+Performance can be further improved at some cost of security by bypassing the I/O memory management unit (IOMMU) for DMA:
+
+```text
+iommu.passthrough=1
+```