Is this a hardware or a software issue?

Memory failures can look like either layer depending on the symptom. The discriminator is the resolution of the symptom to the recommended fix: if applying the steps under "How to fix it" eliminates the symptom, this is a software/configuration class issue regardless of the hardware it surfaced on. Repeat the fix on a fresh node to confirm.

How long does the fix typically take?

Most resolutions from this entry take 10 to 30 minutes of engineer time once the diagnosis is confirmed. Long fixes come from skipping the diagnosis step and chasing apparent symptoms (validation drift, memory growth, slow throughput) instead of the actual root cause listed above. Apply the fix in a small experiment first, then roll it forward.

Does this affect inference or only training?

Primarily this is a memory failure observed during training, but the same misconfiguration can leak into downstream evaluation and serving. Treat the prevention checklist as a guardrail: any pipeline that touches a trained checkpoint should re-validate the failure mode before promoting the model.

What's the cheapest way to confirm this is the problem?

Cheapest signal: reproduce the symptom on a 1-GPU toy run with the same configuration. If the toy run exhibits the same behavior, the cause is the configuration rather than the cluster. If only the multi-GPU run is affected, the failure is a distributed interaction, so Kubernetes Pod Lifecycle is the most likely layer to inspect.

Can the Denpex platform detect this automatically?

Yes. Denpex correlates the symptoms in this entry against your training logs in real time and surfaces the failure taxonomy, root cause, and exact remediation command on the console. Three full diagnoses are included free during signup, and the encyclopedia entry you are reading is generated from the same signal library that powers the platform.

What related failures should I check next?

Closely related failures cluster around #Monitoring. After applying this fix, validate against the related entries below to confirm no overlapping cause is masking as this one. Engineers routinely discover that the dominant failure mode is actually a second, sibling failure compounded on top.

Will this recur after the fix?

Applied once with the prevention checklist, this failure does not recur under normal operation. The recurring variant most engineers encounter is the re-emergence of the same symptom on a different model or stack after Monitoring is upgraded. Pin compatible versions and rerun the prevention smoke test on every dependency change.

Is there a fingerprint I can monitor?

Yes. Application stops processing requests or model training halts indefinitely. is the highest-signal fingerprint. Wire a metric or alert on that signal (or its absence after the fix) so you can detect the recurrence automatically. The Denpex platform encodes this exact fingerprint and surfaces it directly in the dashboard.

What is the official documentation that covers this?

Reference documentation is listed in the References section at the bottom of this entry. The most authoritative URLs are the upstream framework docs and the issue trackers cited; the Denpex entry synthesizes both into the executive, engineer, and on-call perspectives so each audience can act without reading every linked source.

Does this entry include working code?

Yes. The "Code Examples" section contains copy-paste-ready snippets that target the most common stacks (PyTorch, Hugging Face Trainer, DeepSpeed, Megatron-LM, vLLM/Transformers). Each snippet is annotated with why it works so you can adapt the pattern to your own framework without losing fidelity.

Silent Pod GPU OOM Hang

Q: What does this failure look like in production?

In production this failure typically appears during the first tens-to-hundreds of training steps: loss curves become non-monotonic, validation metrics plateau above the baseline, and downstream checkpoints either diverge or fail to improve. Engineers frequently misread it as data drift when the underlying mechanism is a cuda out of memory (oom) error is an application-level exception thrown by the cuda runtime to the framework (e.g., pytorch). unlike a system ram oom where the linux kernel's oom-killer sends a sigkill (resulting in an 'oomkilled' pod state), a cuda oom does not automatically terminate the process. if the application catches the exception but fails to exit gracefully, the container remains alive in a deadlocked or idle state.. Validating against the symptom list in this entry is the fastest way to confirm the diagnosis.

Q: How does this scale from 1 GPU to 1000 GPUs?

At single-GPU scale the symptom usually looks like slow convergence or a single anomalous loss value. At 64+ GPU scale, distributed interactions amplify a cuda out of memory (oom) error is an application-level exception thrown by the cuda runtime to the framework (e.g., pytorch). unlike a system ram oom where the linux kernel's oom-killer sends a sigkill (resulting in an 'oomkilled' pod state), a cuda oom does not automatically terminate the process. if the application catches the exception but fails to exit gracefully, the container remains alive in a deadlocked or idle state. through collectives, and the failure can manifest as a full job abort. Always reproduce the fix at the smallest cluster configuration that still exhibits the symptom before promoting to production scale.

A CUDA Out Of Memory (OOM) error is an application-level exception thrown by the CUDA runtime to the framework (e.g., PyTorch). Unlike a system RAM OOM where the Linux kernel's OOM-killer sends a SIGKILL (resulting in an 'OOMKilled' pod state), a CUDA OOM does not automatically terminate the process. If the application catches the exception but fails to exit gracefully, the container remains alive in a deadlocked or idle state.

Quick answer

A CUDA Out Of Memory (OOM) error is an application-level exception thrown by the CUDA runtime to the framework (e.

Symptom: RuntimeError: CUDA out of memory.
Root cause: A CUDA Out Of Memory (OOM) error is an application-level exception thrown by the CUDA runtime to the framework (e.g., PyTorch).
Recommended fix: Crash the Application Modify app code: try { ... } except RuntimeError as e: if 'CUDA out of memory' in str(e): sys.exit(1) Forces the process to exit with a non-zero code when a CUDA OOM occurs, allowing Kubernetes to detect the failure and restart the pod according to its restartPolicy.
How Denpex helps: Denpex matches Silent Pod GPU OOM Hang across every rank in a distributed run and reports which rank failed first, so you act on the initiating node instead of the loudest one.

Memory#Monitoring

What this failure is

Silent Pod GPU OOM Hang is a Memory failure seen during ML training runs. A CUDA Out Of Memory (OOM) error is an application-level exception thrown by the CUDA runtime to the framework (e.g., PyTorch). Unlike a system RAM OOM where the Linux kernel's OOM-killer sends a SIGKILL (resulting in an 'OOMKilled' pod state), a CUDA OOM does not automatically terminate the process. If the application catches the exception but fails to exit gracefully, the container remains alive in a deadlocked or idle state. Common tags: Monitoring.

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Why it happens (the mechanism)

Kubernetes has no native visibility into GPU VRAM. As far as the kubelet is concerned, the container process PID is still running successfully. Monitoring tools relying solely on cAdvisor metrics will miss the failure entirely.

What you'll observe

RuntimeError: CUDA out of memory.
Tried to allocate <X> MiB

Common symptoms and what they mean

Symptom	Why it happens
Application stops processing requests or model training halts indefinitely.	A CUDA Out Of Memory (OOM) error is an application-level exception thrown by the CUDA runtime to the framework (e.g., PyTorch). Unlike a system RAM OOM where the Linux kernel's OOM-killer sends a SIGKILL (resulting in an 'OOMKilled' pod state), a CUDA OOM does not automatically terminate the process. If the application catches the exception but fails to exit gracefully, the container remains alive in a deadlocked or idle state.
Kubernetes reports the Pod status as 'Running' with 0 restarts.	A CUDA Out Of Memory (OOM) error is an application-level exception thrown by the CUDA runtime to the framework (e.g., PyTorch). Unlike a system RAM OOM where the Linux kernel's OOM-killer sends a SIGKILL (resulting in an 'OOMKilled' pod state), a CUDA OOM does not automatically terminate the process. If the application catches the exception but fails to exit gracefully, the container remains alive in a deadlocked or idle state.
Standard resource metrics (CPU/RAM) appear completely normal.	A CUDA Out Of Memory (OOM) error is an application-level exception thrown by the CUDA runtime to the framework (e.g., PyTorch). Unlike a system RAM OOM where the Linux kernel's OOM-killer sends a SIGKILL (resulting in an 'OOMKilled' pod state), a CUDA OOM does not automatically terminate the process. If the application catches the exception but fails to exit gracefully, the container remains alive in a deadlocked or idle state.

Which systems are affected

Kubernetes Pod Lifecycle
CUDA Runtime
PyTorch / TensorFlow

How to confirm this is the problem

Use this checklist to test the hypothesis against a small reproduction. No single line proves the root cause, so preserve the preceding events and compare one variable at a time.

✓kubectl logs <pod-name> | grep -i 'CUDA out of memory'
✓Query DCGM Exporter metrics for 'DCGM_FI_DEV_XID_ERRORS' matching Xid 31 (Memory Page Fault/OOM).

Searchable error signature

search key

RuntimeError: CUDA out of memory.

Use this text as a lookup key in logs and upstream issue trackers. It is not presented as a captured customer log. Confirm the cause from your own preceding events, versions, configuration and the cited references.

The fix and the prevention pattern

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Root cause

A CUDA Out Of Memory (OOM) error is an application-level exception thrown by the CUDA runtime to the framework (e.g., PyTorch). Unlike a system RAM OOM where the Linux kernel's OOM-killer sends a SIGKILL (resulting in an 'OOMKilled' pod state), a CUDA OOM does not automatically terminate the process. If the application catches the exception but fails to exit gracefully, the container remains alive in a deadlocked or idle state.

The fix and how to prevent it

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References

↗PyTorch CUDA OOM Handling

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