forked from roger/k3s-cluster
103 lines
4.9 KiB
Markdown
103 lines
4.9 KiB
Markdown
# llama.cpp (llama-server)
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In-cluster LLM inference via llama.cpp's `llama-server`, serving local models on
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the NUCBox APU (AMD Ryzen AI Max 395 / Strix Halo, Radeon 8060S, 128 GiB unified
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memory: 32 GiB RAM / 96 GiB VRAM).
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This replaces the bare-metal Ollama setup for models that benefit from
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always-loaded weights + tuned batching. LiteLLM (`litellm/`) points at these
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in-cluster Services instead of the external `10.88.20.12:11434` Ollama endpoint.
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## Layout
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One Deployment + Service **per model**, all in namespace `llamacpp`, all pinned
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to the NUCBox (`nodeSelector: {kubernetes.io/arch: amd64, hardware: high-memory}`):
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| Alias | Model | GGUF | Service |
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|-------------------|----------------------------|-------------------------------------------------------|-------------------------------------------|
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| `qwen3.6-27b` | Qwen3.6-27B (dense) | unsloth/Qwen3.6-27B-MTP-GGUF (Q4_K_XL, ~16 GiB) | `llamacpp-qwen36-27b.llamacpp:80` |
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| `qwen3.6-35b-a3b` | Qwen3.6-35B-A3B (MoE/flash)| unsloth/Qwen3.6-35B-A3B-MTP-GGUF (Q4_K_XL, ~20 GiB) | `llamacpp-qwen36-35b-a3b.llamacpp:80` |
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The 35B-A3B is a Mixture-of-Experts model (3B active params per token), so
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inference is significantly faster than the dense 27B despite more total weights —
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hence the "flash" label. Use it for latency-sensitive workloads; use the 27B for
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deeper reasoning.
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Model files are downloaded idempotently by an initContainer into a shared
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hostPath PVC (`/data/llamacpp/models` on the NUCBox), so pods survive reboots
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without re-downloading.
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## GPU / Vulkan
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The `server-vulkan` image (`ghcr.io/ggml-org/llama.cpp:server-vulkan`) bundles
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the Mesa/RADV Vulkan driver, which supports the Radeon 8060S (RDNA 3.5). Full
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layer offload (`-ngl 999`) puts model weights entirely in the 96 GiB VRAM pool.
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The container mounts `/dev/dri` and runs `privileged: true` — the simplest
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reliable way to give Vulkan access to the DRM render node on k3s without a
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device plugin. Tighten later with `supplementalGroups` (the host's `render`
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group GID) if desired.
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### Verify the GPU is actually used
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```bash
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kubectl logs -n llamacpp deploy/llamacpp-qwen36-27b | grep -iE 'vulkan|gpu|offload|device'
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kubectl logs -n llamacpp deploy/llamacpp-qwen36-35b-a3b | grep -iE 'vulkan|gpu|offload|device'
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```
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If only a CPU device shows up, the container can't see the GPU — check that
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`/dev/dri/renderD128` exists on the NUCBox and that the `amdgpu` module is loaded.
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## VRAM budget (both models co-resident)
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Both models run simultaneously on the same 96 GiB VRAM pool. Approximate usage:
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| Model | Weights | KV cache (131k×4 for a3b, 32k×4 for 27b) | Subtotal |
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|-------------------|----------|-------------------------------------------|----------|
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| qwen3.6-27b | ~16 GiB | ~8 GiB (32k total, 8k/slot) | ~24 GiB |
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| qwen3.6-35b-a3b | ~20 GiB | ~9 GiB (131k total, 33k/slot) | ~29 GiB |
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| **Total** | | | **~53 GiB** |
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~43 GiB headroom — very comfortable. The MoE's KV cache is tiny (~72 KiB/token
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vs the dense 27B's ~256 KiB/token), so large context is nearly free.
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## Tuning
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The key knobs (in each `deployment-*.yaml`):
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- `-ngl 999` — offload all layers to GPU. Reduce only if VRAM is tight.
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- `-c 131072` (35b-a3b) / `32768` (27b) — total KV-cache context. With `-np 4`
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the 35b-a3b gets 32768 tokens per slot (enough for the full SOUL.md + prompt);
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the 27b gets 8192 per slot. The MoE's KV cache is ~72 KiB/token so large
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context is cheap; the dense 27B's is ~256 KiB/token. Raise the 27B's `-c` too
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if interactive sessions hit the context limit.
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- `-np 4` — parallel slots (concurrent requests). Each extra slot multiplies
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KV-cache VRAM usage. Bump higher on the flash model if you need more
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throughput (it has VRAM headroom).
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- `--threads 8` — CPU threads for sampling/overhead. Mostly irrelevant under
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full GPU offload; tune if CPU-bound.
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## Memory accounting
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k8s sees only the ~32 GiB system RAM as allocatable (the 96 GiB VRAM is
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reserved by firmware and managed by `amdgpu`). The model weights and KV cache
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live in VRAM and are **not** counted against the container's cgroup memory
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limit — that limit only covers CPU-side overhead and the mmap'd GGUF pages
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during load. If the pod is OOM-killed during model load, raise the memory limit.
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## Adding a model
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1. Copy `deployment-qwen36-27b.yaml` → `deployment-<new>.yaml`; change the
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`model:` label, GGUF URL/file, `--alias`, and Service name.
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2. Point LiteLLM at it in `litellm/litellm.yaml`:
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```yaml
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- model_name: <alias>
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litellm_params:
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model: openai/<alias>
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api_base: http://<service>.llamacpp/v1
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api_key: "sk-no-auth"
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```
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3. (No gen-apps.sh change needed — the `llamacpp` app already syncs the whole
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directory recursively.)
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4. Check the VRAM budget table above — two large models may not coexist.
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