Report per-GPU memory at container instance registration

[harishxr]

Summary

ecs-init discovers per-GPU usable memory (NVML v2 Total - Reserved) during Setup and persists it as a UUID->MiB map in the GPU info file. The agent loads the map and populates PlatformDevice.GpuInfo.MemoryInMiB when building
the RegisterContainerInstance payload, so the control plane can size GPUs for MPS memory-based placement.

Implementation details

• ecs-init (ecs-init/gpu/nvidia_gpu_manager.go): new DetectGPUMemory() iterates over each device and computes usable memory with NVML v2 (DeviceGetMemoryInfo_v2), usable = (Total - Reserved) / MiB. Results are stored as GPUMemoryMiB map[string]uint64 (UUID -> MiB) and serialized to the GPU info file. Called from Setup().
• agent (agent/gpu/nvidia_gpu_manager_unix.go): reads the matching GPUMemoryMiB field from the info file in Initialize(), and SetDevices() sets PlatformDevice.GpuInfo = &GpuPlatformDeviceInfo{MemoryInMiB: ...} when a UUID has a known value. Left nil for GPUs without a value, so legacy hosts are unaffected.

Backward compatible and additive: the field is omitempty on both sides, so older agents/hosts that do not report it send nothing, and the control plane treats it as optional.

Testing

• On host nvidia-gpu-info.json GPUMemoryMiB = 22563, matching nvidia-smi (23034 total - 471 reserved).

# sudo cat /var/lib/ecs/gpu/nvidia-gpu-info.json
{"DriverVersion":"580.159.03","GPUIDs":["GPU-cc922717-b2bb-b68f-d7da-7e2ac056c6fb"],"GPUMemoryMiB":{"GPU-cc922717-b2bb-b68f-d7da-7e2ac056c6fb":22563},"MpsControlBinaryPresent":true,"MpsServiceEnabled":true,"HasVGPU":false}[root@ip-172-31-37-203 bin]#

• CloudTrail RegisterContainerInstance requestParameters.platformDevices[0] shows gpuInfo.memoryInMiB = 22563 from this agent build, confirming the field reaches the control plane on the wire.

"platformDevices": [
--
{
"id": "GPU-cc922717-b2bb-b68f-d7da-7e2ac056c6fb",
"type": "GPU",
"gpuInfo": {
"memoryInMiB": 22563
}
}
]

New tests cover the changes: yes

Description for the changelog

Enhancement - Report per-GPU memory at container instance registration for GPU sharing

Additional Information

Does this PR include breaking model changes? If so, Have you added transformation functions? No

Does this PR include the addition of new environment variables in the README? No

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[amogh09]

What is the case when memory could be missing?

[harishxr]

Potential cases:

• NVML does not return a response due to some reason when we query for memory, memory will be missing in such a case.
• Agent version is newer than init version, ecs-init will not be able to write the gpuMemory to the gpu info file where agent reads from. In that case, memory will be empty as well.

[amogh09]

We should think about how we can better surface such errors to customers. Silently registering less capacity is not ideal.

[amogh09]

Can this mismatch be caught in DescribeContainerInstances response vs EC2 DescribeInstances or something like that?

[harishxr]

Discussed offline