From 4f33b16411ff9810ad3b4af0de2605a35ca19b1a Mon Sep 17 00:00:00 2001
From: Simon Gardling <titaniumtown@proton.me>
Date: Thu, 9 Apr 2026 14:02:53 -0400
Subject: [PATCH] llama.cpp: thing

---
 flake.lock             |  6 +++---
 services/llama-cpp.nix | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/flake.lock b/flake.lock
index 4b64d4f..429d531 100644
--- a/flake.lock
+++ b/flake.lock
@@ -325,11 +325,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1775614184,
-        "narHash": "sha256-OYwr36LLVIeEqccN1mJ2k6vCsFocboCQJnbtne415Ig=",
+        "lastModified": 1775754125,
+        "narHash": "sha256-4udYhEvii0xPmRiKXYWLhPakPDd1mJppnEFY6uWdv8s=",
         "owner": "TheTom",
         "repo": "llama-cpp-turboquant",
-        "rev": "eea498c42716519e58baf2d9600d2e2b41839255",
+        "rev": "8590cbff961dbaf1d3a9793fd11d402e248869b9",
         "type": "github"
       },
       "original": {
diff --git a/services/llama-cpp.nix b/services/llama-cpp.nix
index 25015c8..b7470f9 100644
--- a/services/llama-cpp.nix
+++ b/services/llama-cpp.nix
@@ -50,17 +50,40 @@ in
       "4096"
       "-ub"
       "4096"
+      "--parallel"
+      "2"
     ];
   };
 
   # have to do this in order to get vulkan to work
   systemd.services.llama-cpp.serviceConfig.DynamicUser = lib.mkForce false;
 
+  # ANV driver's turbo3 shader compilation exceeds the default 8 MB thread stack.
+  systemd.services.llama-cpp.serviceConfig.LimitSTACK = lib.mkForce "67108864"; # 64 MB soft+hard
+
   # llama-server tries to create ~/.cache; ProtectSystem=strict + impermanent
   # root make /root read-only. Give it a writable cache dir and point HOME there.
   systemd.services.llama-cpp.serviceConfig.CacheDirectory = "llama-cpp";
   systemd.services.llama-cpp.environment.HOME = "/var/cache/llama-cpp";
 
+  # turbo3 KV cache quantization runs a 14-barrier WHT butterfly per 128-element
+  # workgroup in SET_ROWS. With 4 concurrent slots and batch=4096, the combined
+  # GPU dispatch can exceed the default i915 CCS engine preempt timeout (7.5s),
+  # causing GPU HANG -> ErrorDeviceLost. Increase compute engine timeouts.
+  # Note: batch<4096 is not viable -- GDN chunked mode needs a larger compute
+  # buffer at smaller batch sizes, exceeding the A380's 6 GB VRAM.
+  # '+' prefix runs as root regardless of service User=.
+  systemd.services.llama-cpp.serviceConfig.ExecStartPre = [
+    "+${pkgs.writeShellScript "set-gpu-compute-timeout" ''
+      for f in /sys/class/drm/card*/engine/ccs*/preempt_timeout_ms; do
+        [ -w "$f" ] && echo 30000 > "$f"
+      done
+      for f in /sys/class/drm/card*/engine/ccs*/heartbeat_interval_ms; do
+        [ -w "$f" ] && echo 10000 > "$f"
+      done
+    ''}"
+  ];
+
   # upstream module hardcodes --log-disable; override ExecStart to keep logs
   # so we can see prompt processing progress via journalctl
   systemd.services.llama-cpp.serviceConfig.ExecStart = lib.mkForce (