From 2f055d9fc55b0ab5ff9996d99bce4d7e331db879 Mon Sep 17 00:00:00 2001
From: Aleix Roca Nonell <aleix.rocanonell@bsc.es>
Date: Thu, 11 May 2023 17:25:48 +0200
Subject: [PATCH] Set intel_pstate=passive and disable frequency boost

---
 xeon08/configuration.nix |  1 +
 xeon08/cpufreq.nix       | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 xeon08/cpufreq.nix

diff --git a/xeon08/configuration.nix b/xeon08/configuration.nix
index 519c954..7899173 100644
--- a/xeon08/configuration.nix
+++ b/xeon08/configuration.nix
@@ -6,6 +6,7 @@
     #(modulesPath + "/installer/netboot/netboot-minimal.nix")
 
     ./kernel/kernel.nix
+    ./cpufreq.nix
     ./fs.nix
     ./users.nix
     ./slurm.nix
diff --git a/xeon08/cpufreq.nix b/xeon08/cpufreq.nix
new file mode 100644
index 0000000..29498c4
--- /dev/null
+++ b/xeon08/cpufreq.nix
@@ -0,0 +1,40 @@
+{ lib, ... }:
+
+{
+  # Disable frequency boost by default. Use the intel_pstate driver instead of
+  # acpi_cpufreq driver because the acpi_cpufreq driver does not read the
+  # complete range of P-States [1]. Use the intel_pstate passive mode [2] to
+  # disable HWP, which allows a core to "select P-states by itself". Also, this
+  # disables intel governors, which confusingly, have the same names as the
+  # generic ones but behave differently [3].
+
+  # Essentially, we use the generic governors, but use the intel driver to read
+  # the P-state list.
+
+  # [1] - https://www.kernel.org/doc/html/latest/admin-guide/pm/intel_pstate.html#intel-pstate-vs-acpi-cpufreq
+  # [2] - https://www.kernel.org/doc/html/latest/admin-guide/pm/intel_pstate.html#passive-mode
+  # [3] - https://www.kernel.org/doc/html/latest/admin-guide/pm/intel_pstate.html#active-mode
+  # https://www.kernel.org/doc/html/latest/admin-guide/pm/cpufreq.html
+
+  # set intel_pstate to passive mode
+  boot.kernelParams = [
+    "intel_pstate=passive"
+  ];
+  # Disable frequency boost
+  system.activationScripts = {
+    disableFrequencyBoost.text = ''
+      echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
+    '';
+  };
+
+  ## disable intel_pstate
+  #boot.kernelParams = [
+  #  "intel_pstate=disable"
+  #];
+  ## Disable frequency boost
+  #system.activationScripts = {
+  #  disableFrequencyBoost.text = ''
+  #    echo 0 > /sys/devices/system/cpu/cpufreq/boost
+  #  '';
+  #};
+}