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serverAppConfigs/serverAppConfigs-docs/LLM/frank-npu.md
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Frank 34a30d8505 docs(iommu): record the executed flip to iommu=pt and its measured cost of nothing 
Window 01:24-01:35. Byte-identical A/B (rebuild proved it: same 1,287,656 B corpus,
same billed token counts 59,024 / 21,568): cold prefill 1,585.1 -> 1,616.0 t/s
(+2.0 %), warm 208,531 -> 214,131, needle hit/hit both boots. The 13-16 % that
justified amd_iommu=off since 2026-09-11 does not exist on this host; the decode
delta (-9.7 %) is instrument noise -- three repeats of one request on the same boot
gave 31.8/46.9/47.8 t/s.

NPU precondition restored: amdxdna bound 0000:c6:00.1 (driver 0.7.0, firmware
amdnpu/17f0_11/npu_7.sbin), group 26 identity, PASID width 10, /dev/accel/accel0
root:render with dank in render. No endpoint deployed, so frank-npu stays retired
-- only its rationale changes. Gates: 0 failed units, 32 groups (31 identity + the
SD reader's DMA quirk), iGPU c5:00.0 identity with ATS, dragoon ledger unchanged
(74.1 GiB, no clamp, listening at 39.8 s).

Deferred on purpose: the pp_dpm_fclk pin (changes iGPU timing for everyone, nothing
co-runs yet) and PerfOpt (7.0.0-38 has zero perfopt symbols, 26.04 caps at 7.0.0-38.38).
Re-keyed: decision record banner/front matter/verification/revert + new execution
section, frank-npu rationale, AGENTS key lesson, both index pages.
2026-10-18 01:34:17 -07:00

7.8 KiB
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type, title, description, tags, timestamp
type title description tags timestamp
reference frank-npu (retired) — FLM NPU endpoint on Dankclaw The retired FastFlowLM endpoint on Dankclaw's XDNA2 NPU — what it served, why it died on 2026-09-11 with the amd_iommu=off decision, and where every dependent route went.
flm
fastflowlm
xdna2
npu
dankclaw
frank-npu
retired
2026-09-11

frank-npu — the retired FLM NPU endpoint

RETIRED 2026-09-11. The endpoint is gone by operator decision, together with the IOMMU configuration it required — see dankclaw-iommu-translation-off. The service unit, env file and serve script are staged in serverAppConfigs/.AGENTTRASH/ (suffixed .flm-npu), and the host unit is stopped and masked.

The third inference endpoint on Dankclaw: a FastFlowLM (FLM) v1.0.1 server (/usr/bin/flm, dpkg fastflowlm) on the XDNA2 NPU (50 TOPS), serving the whole local model registry on port 7771 and routing per request by the exact FLM registry tag. Its one capability the iGPU fleet lacked was sight — and briefly sound: the Gemma4 E4B IT NPU2 pack carries both a vision and an audio tower, which is why the service ran that pack rather than the uncensored-but-text-only alternative.

This page is kept as the retirement record. The operational detail below was live-verified while the service ran and remains accurate about FLM's shape.

Why it is retired

The replacement large-model runtime is worth 13–16 % of prefill if the kernel boots with amd_iommu=off instead of iommu=pt, measured by the upstream project on this exact silicon. That single flag is the whole decision:

  • With IOMMU off there is no PASID/SVA state, and the XDNA2 driver cannot hand out /dev/accel/accel0 — every open fails with err=-19 ("No such device"). That is precisely the failure the endpoint was rescued from on 2026-08-30, recorded in the next section.
  • iommu=pt was recorded here as "not a middle ground", on the theory that the passthrough domain still costs the vendor's prefill number. That claim is dead: the host flipped to iommu=pt on 2026-10-18 and the local A/B on byte-identical traffic measured the cost at nothing (+2.0 % cold prefill, 1,616 t/s at 59k tokens). Identity mode does keep a 1:1 page walk plus ATS/PRI/PASID/GCR3 armed for the iGPU — worth 2–4 % on this silicon class, and AMD PerfOpt (Linux 7.4, merged 2026-09-24) removes it outright by enforcing only the IR/IW permission bits for the privileged iGPU — but nothing waits on that now.
  • The precondition is satisfied; the endpoint is still not deployed. amdxdna binds 0000:c6:00.1 (driver 0.7.0, firmware amdnpu/17f0_11/npu_7.sbin), the NPU sits in IOMMU group 26 identity with PASID width 10, /dev/accel/accel0 is crw-rw---- root:render 261,0 and dank is in render — so a revival quadlet needs AddDevice=/dev/accel/accel0 + GroupAdd=keep-groups, the ComfyUI /dev/kfd pattern. Kernel versions to avoid: 6.18–6.18.7 disables SVA outright. Full census in dankclaw-iommu-translation-off § 2026-10-18 execution.
  • The operator took the vendor's prefill figure on the September evidence, so the NPU endpoint went — and it stays retired because nobody has asked for a model on it, not because the hardware is unreachable.

Consequences accepted at retirement: audio input left the fleet with no replacement (halogen reads images only, no audio or video), and the surviving image path is halogen's vision tower on frank-dragoon.

Where its routes went

consumer setting now
Hermes auxiliary.vision dankclaw-large / frank-dragoon (halogen vision tower)
Hermes auxiliary.title_generation dankserver-small / frank-zealot
harness (~/.omp/agent/models.yml) modelRoles.vision llamacpp (dankclaw) / frank-dragoon
harness modelRoles.tiny llamacpp (dankserver) / frank-zealot
harness modelRoles.task llamacpp (dankclaw) / frank-dragoon:medium

The flm (dankclaw-npu) provider block was removed from the harness model config, and the dankclaw-npu provider from Hermes's live config.yaml.

What it was

Field Value
Runtime FLM v1.0.1 (/usr/bin/flm, dpkg fastflowlm) on the XDNA2 NPU
Service frank-npu.service (systemd system unit, User=dank, Restart=on-failure, RestartSec=10, LimitMEMLOCK=infinity)
Files (archived) scripts/frank-npu.env, scripts/serve-frank-npu.sh, scripts/frank-npu.service
Port 7771 on 0.0.0.0
Power mode FLM_PMODE=turbo — nothing else used the NPU, so the top power mode cost no neighbour anything
Context FLM_CTX_LEN=131072 (128K, the verified maximum on this box)
Vision/audio FLM_ASR=0; the E4B pack answers images through its own vision tower, and FLM_ASR=1 would have added Whisper-V3-Turbo-NPU2 (+0.62 GB) and /v1/audio/transcriptions

The serve script exported FLM_CONFIG_PATH=/home/dank/.config/flm/model_list.json and FLM_XCLBIN_PATH=/home/dank/.config/flm/xclbins, with kernels symlinked from /opt/fastflowlm/share/flm/xclbins/ into the per-pack directories, so a tag swap was an env-file edit rather than a script edit.

API contract (as it behaved)

  • The endpoint served the whole local registry (36 tags at first deploy) on one port; /v1/models listed them all. Chat completions routed per request by the exact registry tag in the model field — never a service alias.
  • Unknown tags did not 404: /v1/chat/completions answered HTTP 200 with a flat error body {"error":"Failed to load <tag> model!"} and no choices. Status-code-only clients silently got an empty response.
  • Health was GET /v1/version; FLM has no /health route.
  • The NPU is a single-lane device — generations serialized FIFO. It was a background/triage endpoint, not interactive multi-user chat.

The IOMMU/SVA root cause (first deploy crashed, fixed 2026-08-30)

First deploy crash-looped every 10 s with Error: Open /dev/accel/accel0 failed (err=-19): No such device. The chain, all live-verified on the host:

  1. amdxdna_drm_open failed SVA bind with ret -19 for every client — the XDNA2 driver cannot hand out the accel device without PASID/SVA.
  2. SVA requires the AMD IOMMU to be enabled, and the kernel cmdline then carried iommu=off. With IOMMU off there are no IOMMU groups and no PASID state; PASIDCtl: Enable- was observed on 0000:c5:00.1.
  3. The fix was iommu=pt: passthrough keeps the iGPU default domain identity-mapped (no DMA-translation overhead for frank-dragoon) while enabling the IOMMU hardware and PASID that the driver's SVA bind needs.
  4. Post-boot verification: /sys/kernel/iommu_groups/ populated (30 groups), zero SVA bind device failed entries since boot, accel0 recreated at boot, service active with NRestarts=0.

The same root cause explained the older amdgpu 0000:c4:00.0: no vmid pasid mapping supported kernel line — a consequence of IOMMU-off, not a GPU fault.

The standing rule this produced — "never set iommu=off on this host again" — has been superseded: the NPU it protected is retired by decision, and amd_iommu=off is now intentional. See dankclaw-iommu-translation-off for the current posture and how to revert it.

Client wiring (historical)

The pi/harness model config registered this endpoint with the exact FLM registry tag as the model id and baseUrl http://192.168.0.143:7771/v1. Both that provider block and Hermes's dankclaw-npu provider were removed at retirement; the routes are mapped in the table above.

Citations

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