hugepages changes

configuration.nix

@@ -118,6 +118,9 @@
 
   hardware.intelgpu.driver = "xe";
 
+  # Per-service 2MB hugepage budget calculated in service-configs.nix.
+  boot.kernel.sysctl."vm.nr_hugepages" = service_configs.hugepages_2m.total_pages;
+
   boot = {
     # 6.12 LTS until 2026
     kernelPackages = pkgs.linuxPackages_6_12_hardened;

service-configs.nix

@@ -60,6 +60,7 @@ rec {
   postgres = {
     socket = "/run/postgresql";
     dataDir = services_dir + "/sql";
+    shared_buffers_m = 128; # PostgreSQL default; update if you change shared_buffers
   };
 
   immich = {
@@ -150,4 +151,25 @@ rec {
     moviesDir = torrents_path + "/media/movies";
     tvDir = torrents_path + "/media/tv";
   };
+
+  # Per-service 2MB hugepage budget.
+  # Each value is the service's hugepage consumption in MB, derived from
+  # its actual memory configuration. The kernel sysctl vm.nr_hugepages
+  # is set to total_pages so every service gets what it needs.
+  hugepages_2m = rec {
+    page_size_m = 2;
+
+    # RandomX dataset (2048MB) + cache (256MB) = 2304MB per instance.
+    # Both monerod and p2pool allocate their own full copy via MAP_HUGETLB.
+    randomx_instance_m = 2048 + 256;
+
+    services = {
+      minecraft_m = minecraft.memory.heap_size_m; # JVM heap via -XX:+UseLargePages
+      monerod_m = randomx_instance_m; # block verification dataset
+      p2pool_m = randomx_instance_m; # mining dataset
+      postgres_m = postgres.shared_buffers_m; # huge_pages = try (default)
+    };
+
+    total_pages = builtins.foldl' (a: b: a + b) 0 (builtins.attrValues services) / page_size_m;
+  };
 }

services/minecraft.nix

@@ -27,14 +27,6 @@
   boot.kernel.sysctl = {
     # Disable autogroup for better scheduling of game server threads
     "kernel.sched_autogroup_enabled" = 0;
-
-    # We want to determine the number of hugepages based on how many minecraft needs.
-    # This can be determined by dividing the heap size by the size of a large page.
-    # Doing this gives us how many large pages are needed.
-    # Then we add 300 to give some headroom.
-    "vm.nr_hugepages" =
-      (service_configs.minecraft.memory.heap_size_m / service_configs.minecraft.memory.large_page_size_m)
-      + 300;
   };
 
   services.minecraft-servers = {