From 70f99a5e185ee61609a5c64fbbc87916a42e9909 Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Wed, 25 Jun 2025 14:36:16 +0100
Subject: [PATCH] Add macos-vram helpers

---
 machines/irnbru/configuration.nix |  4 ++++
 modules/base/default.nix          |  1 +
 modules/base/macos-vram.nix       | 36 +++++++++++++++++++++++++++++++
 3 files changed, 41 insertions(+)
 create mode 100644 modules/base/macos-vram.nix

diff --git a/machines/irnbru/configuration.nix b/machines/irnbru/configuration.nix
index c7cc6f5..1f1f28a 100644
--- a/machines/irnbru/configuration.nix
+++ b/machines/irnbru/configuration.nix
@@ -4,6 +4,10 @@
   imports = [ ];
 
   modules = {
+    vram = {
+      wiredLimit = 8;
+      wiredLowWatermark = 20;
+    };
     server = {
       enable = true;
       sshd.enable = true;
diff --git a/modules/base/default.nix b/modules/base/default.nix
index 2825c01..a067035 100644
--- a/modules/base/default.nix
+++ b/modules/base/default.nix
@@ -7,5 +7,6 @@
     ./shell.nix
     ./linux.nix
     ./macos.nix
+    ./macos-vram.nix
   ];
 }
diff --git a/modules/base/macos-vram.nix b/modules/base/macos-vram.nix
new file mode 100644
index 0000000..362b46b
--- /dev/null
+++ b/modules/base/macos-vram.nix
@@ -0,0 +1,36 @@
+{ lib, config, helpers, ... }:
+
+with lib;
+let
+  cfg = config.modules.vram;
+in helpers.darwinAttrs {
+  options.modules.vram = {
+    wiredLimit = mkOption {
+      default = null;
+      description = "Wired Memory Limit in GBs";
+      type = types.nullOr (types.ints.between 2 512);
+    };
+
+    wiredLowWatermark = mkOption {
+      default = null;
+      description = "Wired LWM (Low Watermark) in GBs";
+      type = types.nullOr (types.ints.between 2 512);
+    };
+  };
+
+  config = mkIf (cfg.wiredLimit != null || cfg.wiredLowWatermark != null) {
+    system.activationScripts.postActivation.text = let
+      setWiredLimitMb = optionalString (cfg.wiredLimit != null) ''
+        wired_memsize_mb=$(($(sysctl -n hw.memsize) / 1024 / 1024))
+        sysctl -w iogpu.wired_limit_mb="$((wired_memsize_mb - ${toString (cfg.wiredLimit * 1024)}))"
+      '';
+      setWiredLowWaterMarkMb = optionalString (cfg.wiredLowWatermark != null) ''
+        sysctl -w iogpu.wired_lwm_mb="$((${toString (cfg.wiredLowWatermark * 1024)}))"
+      '';
+    in ''
+      ${setWiredLimitMb}
+      ${setWiredLowWaterMarkMb}
+    '';
+  };
+}
+
-- 
2.51.2