Discovery reports a card in MIG mode as its instances instead of the whole
card, on both paths: nvidia-smi (-L names them, -q -x gives their memory,
ids and processes) and NVML (GetMigMode, GetMaxMigDeviceCount,
GetMigDeviceHandleByIndex, behind an interface so it is tested with a fake).
Each instance has its MIG UUID, its own memory, and a class from the card's
and the profile: a100-80g-mig-3g.40gb. Placement numbers instances
1000 + 100 x card + instance and every view shows them as card/migN.
A replica on MIG runs on exactly one instance: a process opens one MIG
device and instances have no NVLink between them, so tp, pp, gpus or nodes
above one on a MIG class are refused in catalog validation and again in
placement, and the planner offers one instance or none. The agent gives
the engine CUDA_VISIBLE_DEVICES=MIG-<uuid> (no Vulkan device variable on
MIG). Memory and processes are per instance; heat, power and wear the
card's; utilisation is left out rather than reported as zero. A card in MIG
mode with nothing carved stays out of placement with the reason, and
llmgw doctor reports each card's mode and instances and warns of the states
in which nothing can run. ctl nodes, ctl status, the console and the plan
count devices by class. docs/install.md has a MIG section.
Written against fakes of nvidia-smi and NVML output; not yet run on MIG
hardware.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
NVML is the only source of NVLink topology, and that topology is what keeps a
tensor-parallel group off the slow path inside a node. It needs cgo, so it sits
behind the nvml tag and the default build keeps using nvidia-smi.
Discover() picks the backend and falls back to nvidia-smi when NVML fails,
logging the fallback rather than performing it silently: on a node that is meant
to have working NVML, a quiet downgrade hides a broken driver installation and
costs the scheduler its topology.
CI now compiles the tagged build. That immediately paid for itself: ErrNoNVML
was declared only in the untagged file, so the tests did not compile under
-tags nvml. It is now declared where both builds can see it.
Not verified: the NVML path has never run against a driver, because there is no
GPU machine available. The NVLink domains it reports should be treated as
unverified until someone runs `llmgw agent inventory` on a real node.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
ilkerandClaude Opus 5