exclude audiotube app from building

EasyEffects DSP plugins (rnnoise, deepfilternet, crystalizer) drop audio
when the system is under load. Layered workaround with per-optimization
toggles for bisecting impact:

- cgroup-based CPU partitioning: dedicated audio.slice with AllowedCPUs
  pinning, restricted app/session/background slices for everything else
- rlimits so PipeWire's module-rt sets SCHED_FIFO 88 directly instead of
  going through RTKit's priority-10 ceiling
- persistent watcher that re-applies performance governor on audio cores
  (gamemoded/PPD keep resetting it)
- ananicy rule pinning easyeffects to nice -12 for non-RT DSP threads
- znver4-tuned rebuilds of easyeffects and its DSP deps

Master switch + per-feature toggles via lumpiasty.audioRt.*; all enabled
by default on acer host. None of this fully eliminates dropouts on this
thermally constrained laptop but each layer is independently testable.

flake.lock

@@ -44,11 +44,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1778105658,
-        "narHash": "sha256-PxurBCejSjB99wxkpiPTUi4aHSYlfiHzrCwAGuDTRb8=",
+        "lastModified": 1778887053,
+        "narHash": "sha256-0tSElqIlp+tbsMrbxVwzKlF3wrRO2GPGHmDqrMbaphs=",
         "owner": "sadjow",
         "repo": "claude-code-nix",
-        "rev": "f065f848c6a11f93124b09164fa92e8253a0264d",
+        "rev": "faa8786775fa232366f95a6f8dc2de67a1fea0e5",
         "type": "github"
       },
       "original": {
@@ -182,11 +182,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1778144356,
-        "narHash": "sha256-dGM+QCstz/DyLB68+JK5GWyMx4QSqmOJEVgZmy63d/g=",
+        "lastModified": 1779143091,
+        "narHash": "sha256-qxiUVquHM09KOV1aD4We9q0ooPWO4qOc0v9J9NDWSAo=",
         "owner": "nix-community",
         "repo": "home-manager",
-        "rev": "e4419d3123b780d5f4c0bceeace450424387638c",
+        "rev": "736c2084ea750a049ecdbdd7ff5817d2eeeef444",
         "type": "github"
       },
       "original": {
@@ -298,11 +298,11 @@
     },
     "nixos-hardware": {
       "locked": {
-        "lastModified": 1778143761,
-        "narHash": "sha256-lkesY6x2X2qxlqLM7CT2iM/0rP2JB7fruPN3h8POXmI=",
+        "lastModified": 1779099457,
+        "narHash": "sha256-u73aVD/lUmmT3JV+kPDztl7zPwQKd0eobD1AbJltaGs=",
         "owner": "NixOS",
         "repo": "nixos-hardware",
-        "rev": "3bcaa367d4c550d687a17ac792fd5cda214ee871",
+        "rev": "8792fab9d4a6454a9201675f01326f827ce35ead",
         "type": "github"
       },
       "original": {
@@ -314,11 +314,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1777954456,
-        "narHash": "sha256-hGdgeU2Nk87RAuZyYjyDjFL6LK7dAZN5RE9+hrDTkDU=",
+        "lastModified": 1778869304,
+        "narHash": "sha256-30sZNZoA1cqF5JNO9fVX+wgiQYjB7HJqqJ4ztCDeBZE=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "549bd84d6279f9852cae6225e372cc67fb91a4c1",
+        "rev": "d233902339c02a9c334e7e593de68855ad26c4cb",
         "type": "github"
       },
       "original": {

home-modules/pc.nix

@@ -41,6 +41,11 @@
     ];
     programs.librewolf.enable = true;
     services.easyeffects.enable = true;
+    systemd.user.services.easyeffects.Service = lib.mkIf osConfig.lumpiasty.audioRt.cpuPartitioning {
+      # Move easyeffects into audio.slice (defined in modules/desktop/audio-rt.nix)
+      # which has AllowedCPUs=<audioCpus> — pins all DSP work to the reserved cores.
+      Slice = "audio.slice";
+    };
 
     programs.chromium.enable = true;
     programs.chromium.package = pkgs.ungoogled-chromium;

hosts/acer.nix

@@ -23,8 +23,8 @@ rec {
 
   # Kernel
   # boot.initrd.availableKernelModules = [ "xhci_pci" "ahci" "usb_storage" "sd_mod" "rtsx_pci_sdmmc" ];
-  boot.kernelPackages = nixpkgs-linuxeol.legacyPackages."x86_64-linux".linuxKernel.packages.linux_6_19;
-  boot.zfs.package = pkgs.zfs_unstable;
+  boot.kernelPackages = pkgs.linuxKernel.packages.linux_7_0;
+  boot.zfs.package = pkgs.zfs_2_4;
 
   # Swap
   swapDevices = [
@@ -71,6 +71,7 @@ rec {
     amdCpu = true;
     noMitigations = false;
     enablePulseaudio = true;
+    audioRt.enable = true;
     sshd = true;
     users.user = true;
     # users.drugi = true;

hosts/gaming-pc.nix

@@ -53,7 +53,7 @@
 
   # Kernel
   # boot.initrd.availableKernelModules = [ "xhci_pci" "ahci" "usb_storage" "sd_mod" "rtsx_pci_sdmmc" ];
-  boot.kernelPackages = nixpkgs-linuxeol.legacyPackages."x86_64-linux".linuxKernel.packages.linux_6_19;
+  boot.kernelPackages = pkgs.linuxKernel.packages.linux_7_0;
 
   # Swap
   zramSwap = {

modules/default.nix

@@ -20,6 +20,7 @@
     desktop/plasma.nix
     desktop/touchpad.nix
     desktop/pulseaudio.nix
+    desktop/audio-rt.nix
     desktop/tailscale.nix
   ];
 }

modules/desktop/audio-rt.nix

@@ -0,0 +1,233 @@
+{ config, lib, pkgs, ... }:
+
+# Workarounds for audio xruns under CPU load.
+#
+# Each optimization is independently toggleable so behavior can be bisected.
+# `lumpiasty.audioRt.enable` is the master switch; individual sub-flags default
+# to `true` when the master is on and can be flipped per-host to test impact.
+
+let
+  cfg = config.lumpiasty.audioRt;
+
+  marchFlags = " -march=znver4 -O3";
+
+  # ---------------------------------------------------------------------------
+  # Per-build-system helpers (see commit history for rationale on LTO choices).
+  # ---------------------------------------------------------------------------
+  withMarch = pkg: pkg.overrideAttrs (old: {
+    env = (old.env or {}) // {
+      NIX_CFLAGS_COMPILE =
+        ((old.env or {}).NIX_CFLAGS_COMPILE or old.NIX_CFLAGS_COMPILE or "")
+        + marchFlags;
+    };
+  });
+
+  cmakePkg = pkg: pkg.overrideAttrs (old: {
+    env = (old.env or {}) // {
+      NIX_CFLAGS_COMPILE =
+        ((old.env or {}).NIX_CFLAGS_COMPILE or old.NIX_CFLAGS_COMPILE or "")
+        + marchFlags;
+    };
+    cmakeFlags = (old.cmakeFlags or []) ++ [ "-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON" ];
+    preConfigure = (old.preConfigure or "") + "\nexport AR=gcc-ar\n";
+  });
+
+  rustPkg = pkg: pkg.overrideAttrs (old: {
+    RUSTFLAGS = (old.RUSTFLAGS or "") + " -C target-cpu=znver4";
+  });
+
+in
+
+{
+  options.lumpiasty.audioRt = {
+    enable = lib.mkEnableOption "Audio RT scheduling and CPU isolation";
+
+    audioCpus = lib.mkOption {
+      type = lib.types.str;
+      default = "12-15";
+      description = "CPU list reserved for audio services (systemd cpuset syntax).";
+    };
+
+    nonAudioCpus = lib.mkOption {
+      type = lib.types.str;
+      default = "0-11";
+      description = "CPU list for everything else.";
+    };
+
+    # ------ Individual optimization toggles ------
+
+    cpuPartitioning = lib.mkOption {
+      type = lib.types.bool;
+      default = cfg.enable;
+      description = ''
+        Cgroup-based CPU partitioning via dedicated audio.slice and
+        restricted app/session/background slices.
+      '';
+    };
+
+    rtLimits = lib.mkOption {
+      type = lib.types.bool;
+      default = cfg.enable;
+      description = ''
+        Raise rlimits (RTPRIO=95, MEMLOCK=infinity) for the audio group
+        so PipeWire's module-rt can set SCHED_FIFO 88 directly instead
+        of going through RTKit's priority-10 ceiling.
+      '';
+    };
+
+    performanceGovernor = lib.mkOption {
+      type = lib.types.bool;
+      default = cfg.enable;
+      description = ''
+        Keep cpufreq governor `performance` on the audio cores so they
+        stay boosted regardless of measured utilization.
+      '';
+    };
+
+    ananicy = lib.mkOption {
+      type = lib.types.bool;
+      default = cfg.enable;
+      description = ''
+        Run ananicy-cpp with a rule that pins easyeffects to nice -12 so
+        its non-RT DSP threads get scheduler preference under load.
+      '';
+    };
+
+    optimisedBinaries = lib.mkOption {
+      type = lib.types.bool;
+      default = cfg.enable;
+      description = ''
+        Rebuild easyeffects and its DSP dependencies with -march=znver4 -O3
+        (and LTO for cmake builds, target-cpu for rust builds).
+      '';
+    };
+  };
+
+  config = lib.mkMerge [
+
+    # --- Optimised binary builds ---------------------------------------------
+    (lib.mkIf (cfg.enable && cfg.optimisedBinaries) {
+      nixpkgs.overlays = [
+        (final: prev: {
+          easyeffects = cmakePkg (prev.easyeffects.override {
+            fftw          = withMarch prev.fftw;
+            fftwFloat     = withMarch prev.fftwFloat;
+            speexdsp      = withMarch prev.speexdsp;
+            rubberband    = withMarch prev.rubberband;
+            soundtouch    = withMarch prev.soundtouch;
+            zita-convolver          = withMarch prev.zita-convolver;
+            webrtc-audio-processing = withMarch prev.webrtc-audio-processing;
+            rnnoise       = withMarch prev.rnnoise;
+            libebur128    = cmakePkg prev.libebur128;
+            libbs2b       = withMarch prev.libbs2b;
+            lilv          = withMarch prev.lilv;
+            onetbb        = cmakePkg prev.onetbb;
+            calf          = cmakePkg prev.calf;
+            lsp-plugins   = withMarch prev.lsp-plugins;
+            zam-plugins   = withMarch prev.zam-plugins;
+            mda_lv2       = withMarch prev.mda_lv2;
+            deepfilternet = rustPkg  prev.deepfilternet;
+          });
+        })
+      ];
+    })
+
+    # --- RT scheduling rlimits ----------------------------------------------
+    (lib.mkIf (cfg.enable && cfg.rtLimits) {
+      security.pam.loginLimits = [
+        { domain = "@audio"; type = "-"; item = "rtprio";  value = "95"; }
+        { domain = "@audio"; type = "-"; item = "memlock"; value = "unlimited"; }
+        { domain = "@audio"; type = "-"; item = "nice";    value = "-20"; }
+      ];
+      systemd.user.extraConfig = ''
+        DefaultLimitRTPRIO=95
+        DefaultLimitMEMLOCK=infinity
+      '';
+    })
+
+    # --- CPU partitioning (cgroup-based) ------------------------------------
+    #
+    # Cgroup hierarchy under user@.service:
+    #   ├── app.slice         AllowedCPUs=<nonAudioCpus>  (Steam-launched apps)
+    #   ├── session.slice     AllowedCPUs=<nonAudioCpus>  (kwin, plasmashell, kded)
+    #   ├── background.slice  AllowedCPUs=<nonAudioCpus>  (akonadi, polkit)
+    #   └── audio.slice       AllowedCPUs=<audioCpus>     (pipewire, easyeffects)
+    #
+    # Reasoning:
+    #   - No isolcpus= : breaks scheduler load balancing on the rest of the system.
+    #   - No nohz_full= : amd-pstate can't sample utilization in tickless mode
+    #     so cores get clamped at minimum frequency.
+    #   - No rcu_nocbs= : microsecond-scale jitter is irrelevant at 21ms quantum.
+    (lib.mkIf (cfg.enable && cfg.cpuPartitioning) {
+      systemd.user.extraConfig = ''
+        CPUAffinity=${cfg.nonAudioCpus}
+      '';
+      systemd.settings.Manager.CPUAffinity = cfg.nonAudioCpus;
+
+      # Delegate the cpuset controller to user managers so user-level slices
+      # can use AllowedCPUs=.
+      systemd.services."user@".serviceConfig.Delegate = "cpu cpuset io memory pids";
+
+      systemd.user.slices = {
+        app.sliceConfig.AllowedCPUs = cfg.nonAudioCpus;
+        session.sliceConfig.AllowedCPUs = cfg.nonAudioCpus;
+        background.sliceConfig.AllowedCPUs = cfg.nonAudioCpus;
+        audio = {
+          description = "Audio services pinned to reserved CPU cores";
+          sliceConfig.AllowedCPUs = cfg.audioCpus;
+        };
+      };
+
+      # easyeffects.service Slice= is set in home-modules/pc.nix.
+      systemd.user.services.pipewire.serviceConfig.Slice = "audio.slice";
+      systemd.user.services.pipewire-pulse.serviceConfig.Slice = "audio.slice";
+      systemd.user.services.wireplumber.serviceConfig.Slice = "audio.slice";
+    })
+
+    # --- Performance governor on audio cores --------------------------------
+    (lib.mkIf (cfg.enable && cfg.performanceGovernor) {
+      systemd.services.audio-cores-performance = {
+        description = "Keep performance governor on audio cores";
+        wantedBy = [ "multi-user.target" ];
+        after = [ "multi-user.target" ];
+        serviceConfig = {
+          Type = "simple";
+          Restart = "always";
+          RestartSec = "5s";
+          # Expand systemd CPU list ("12-15" / "12,13,14,15") into a flat list.
+          ExecStart = pkgs.writeShellScript "audio-cores-performance" ''
+            cpus=$(echo "${cfg.audioCpus}" | ${pkgs.coreutils}/bin/tr ',' ' ' | \
+              ${pkgs.gawk}/bin/awk '{
+                for (i=1; i<=NF; i++) {
+                  if (match($i, /^([0-9]+)-([0-9]+)$/, m))
+                    for (j=m[1]; j<=m[2]; j++) print j
+                  else print $i
+                }
+              }')
+            while true; do
+              for cpu in $cpus; do
+                cur=$(cat /sys/devices/system/cpu/cpu$cpu/cpufreq/scaling_governor)
+                if [ "$cur" != "performance" ]; then
+                  echo performance > /sys/devices/system/cpu/cpu$cpu/cpufreq/scaling_governor
+                fi
+              done
+              sleep 2
+            done
+          '';
+        };
+      };
+    })
+
+    # --- Ananicy rule for easyeffects ---------------------------------------
+    (lib.mkIf (cfg.enable && cfg.ananicy) {
+      services.ananicy = {
+        enable = true;
+        package = pkgs.ananicy-cpp;
+        extraRules = [
+          { name = "easyeffects"; type = "Audio"; nice = -12; }
+        ];
+      };
+    })
+
+  ];
+}

modules/desktop/plasma.nix

@@ -58,6 +58,9 @@
         # Exclude audiocd-kio due to build failure
         (builtins.filter (pkg: pkg.pname != "audiocd-kio"))
 
+        # Exclude audiotube due to build failure
+        (builtins.filter (pkg: pkg.pname != "audiotube"))
+
         # Exclude plasma-mobile
         (builtins.filter (pkg: pkg.pname != "plasma-mobile"))
       ]) ++ [

modules/desktop/pulseaudio.nix

@@ -20,13 +20,21 @@
       # no need to redefine it in your config for now)
       #media-session.enable = true;
 
+      extraConfig.pipewire."99-quantum" = {
+        "context.properties" = {
+          "default.clock.quantum"     = 1024;
+          "default.clock.min-quantum" = 1024;
+          "default.clock.max-quantum" = 8192;
+        };
+      };
+
       wireplumber.configPackages = [
         (pkgs.writeTextDir "share/wireplumber/wireplumber.conf.d/99-alsa-nova-3.conf" ''
           monitor.alsa.rules = [
             {
               matches = [
                 {
-                  node.name = "alsa_output.usb-SteelSeries_Arctis_Nova_3-00.analog-stereo"
+                  node.name = "alsa_output.usb-SteelSeries_Arctis_Nova_7-00.analog-stereo"
                 }
               ]
               actions = {
@@ -34,7 +42,7 @@
                   audio.format = "S24LE"
                   audio.rate = 96000
                   api.alsa.period-size = 1024
-                  api.alsa.period-num = 4
+                  api.alsa.period-num = 8
                   api.alsa.disable-batch = false
                 }
               }

pkgs/opencode-claude-auth/default.nix

@@ -2,11 +2,11 @@
 
 stdenv.mkDerivation {
   pname = "opencode-claude-auth";
-  version = "1.5.0";
+  version = "1.5.4";
 
   src = fetchurl {
-    url = "https://registry.npmjs.org/opencode-claude-auth/-/opencode-claude-auth-1.5.0.tgz";
-    hash = "sha512-5NSL+x++VTe2ZrFSznXKv7imiKObIBz0QXPuL+g1NAXAcdTGcbEbQBvvHZeIaSBNjmwpY2MR67Yez1f3LlPl7w==";
+    url = "https://registry.npmjs.org/opencode-claude-auth/-/opencode-claude-auth-1.5.4.tgz";
+    hash = "sha256-9iByuNTg/MTD3VGeqpBaBCBaooXm97BuvP0fPXDoPGc=";
   };
 
   dontBuild = true;