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@dhansen-nvidia dhansen-nvidia commented Nov 13, 2025

… (#8805)

Summary by CodeRabbit

  • Refactor
    • Enhanced CPU affinity management for worker processes with NUMA-aware optimization to improve performance on multi-socket CPU systems
    • CPU affinity behavior is configurable via environment variables (TLLM_NUMA_AWARE_WORKER_AFFINITY)
    • Added warning diagnostics for cases where process affinity constraints may impact performance

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@dhansen-nvidia dhansen-nvidia requested a review from a team as a code owner November 13, 2025 01:38
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📝 Walkthrough

Walkthrough

CPU affinity configuration for workers is refactored from implementation in worker.py to a centralized, NUMA-aware approach in BaseWorker. A new utility function replaces prior affinity helpers, integrating NVML-based GPU-to-CPU topology querying and environment-controlled auto-configuration.

Changes

Cohort / File(s) Summary
CPU Affinity Relocation
tensorrt_llm/executor/base_worker.py
Added _configure_affinity(device_id) method to probe NUMA topology, check current affinity constraints via psutil, and conditionally apply NUMA-aware affinity based on environment variables. Invoked during device/rank setup. Added imports: os, psutil, and get_numa_aware_cpu_affinity.
Worker Cleanup
tensorrt_llm/executor/worker.py
Removed os import and affinity-related logic from worker_main that previously retrieved process ID, queried CPU affinity, logged warnings, and cleared affinity.
NUMA-Aware Affinity Utility
tensorrt_llm/llmapi/utils.py
Replaced set_sched_setaffinity() and clear_sched_affinity() with new get_numa_aware_cpu_affinity(device_id). New function queries GPU-to-CPU topology via NVML with error handling, returning a list of recommended CPU IDs. Added imports: ctypes and math.

Sequence Diagram

sequenceDiagram
    participant Worker as BaseWorker.init()
    participant Rank as _get_comm_ranks_device_id()
    participant Affinity as _configure_affinity()
    participant Util as get_numa_aware_cpu_affinity()
    participant NVML as NVML (GPU Topology)
    participant OS as psutil (Current Affinity)

    Worker->>Rank: determine device_id
    Rank->>Affinity: _configure_affinity(device_id)
    
    Affinity->>OS: check current affinity
    rect rgb(220, 240, 255)
        Note over OS: Log warning if constrained
    end
    
    Affinity->>Affinity: check TLLM_NUMA_* env vars
    alt auto-configure enabled or explicit request
        Affinity->>Util: get_numa_aware_cpu_affinity(device_id)
        Util->>NVML: query GPU-CPU topology
        rect rgb(240, 220, 255)
            Note over NVML: Return CPU mask for device
        end
        Util-->>Affinity: return CPU ID list
        rect rgb(220, 255, 220)
            Note over Affinity: Apply affinity to process
        end
    else constrained and no override
        Note over Affinity: Leave affinity unchanged
    end
Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

  • base_worker.py: New _configure_affinity() method with environment variable handling, psutil integration, and conditional affinity application requires careful review of logic flow and edge cases.
  • llmapi/utils.py: NVML integration with initialization/shutdown, error handling, and CPU affinity mask computation logic should be verified for correctness and robustness.
  • NUMA topology querying: Ensure NVML error handling and fallback behavior (defaulting to all CPUs) work as intended across different hardware configurations.

Pre-merge checks and finishing touches

❌ Failed checks (2 warnings)
Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 44.44% which is insufficient. The required threshold is 80.00%. You can run @coderabbitai generate docstrings to improve docstring coverage.
Description check ⚠️ Warning The PR description is mostly a template without substantive content. The Description and Test Coverage sections are completely empty, and the PR Checklist is unchecked. Only the title template instructions are provided. Fill in the Description section explaining what NUMA-aware CPU affinity autoconfig does and why it's needed. Add specific test coverage details for the changes across base_worker.py, worker.py, and utils.py.
✅ Passed checks (1 passed)
Check name Status Explanation
Title check ✅ Passed The title clearly references the NVBugs ID and indicates the feature is a cherry-pick of a specific PR, making the intent of the change transparent and specific.
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Actionable comments posted: 1

📜 Review details

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Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 12fa81c and 6ed9572.

📒 Files selected for processing (3)
  • tensorrt_llm/executor/base_worker.py (4 hunks)
  • tensorrt_llm/executor/worker.py (1 hunks)
  • tensorrt_llm/llmapi/utils.py (2 hunks)
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  • tensorrt_llm/llmapi/utils.py
  • tensorrt_llm/executor/base_worker.py
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Files:

  • tensorrt_llm/executor/worker.py
  • tensorrt_llm/llmapi/utils.py
  • tensorrt_llm/executor/base_worker.py
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  • tensorrt_llm/executor/base_worker.py
🧠 Learnings (1)
📚 Learning: 2025-07-17T09:01:27.402Z
Learnt from: amitz-nv
Repo: NVIDIA/TensorRT-LLM PR: 5616
File: tensorrt_llm/executor/worker.py:375-384
Timestamp: 2025-07-17T09:01:27.402Z
Learning: In tensorrt_llm/executor/worker.py, the LoRA adapter cache optimization logic that checks `is_adapter_in_cpu_cache()` and conditionally passes None for weights/config has a known race condition issue that cannot be solved with simple error handling or verification checks. This is a known limitation that requires a more comprehensive solution.

Applied to files:

  • tensorrt_llm/executor/worker.py
  • tensorrt_llm/executor/base_worker.py
🧬 Code graph analysis (2)
tensorrt_llm/executor/worker.py (1)
tensorrt_llm/llmapi/utils.py (2)
  • print_colored_debug (66-70)
  • print_traceback_on_error (33-44)
tensorrt_llm/executor/base_worker.py (2)
tensorrt_llm/llmapi/utils.py (5)
  • _SyncQueue (389-456)
  • get_numa_aware_cpu_affinity (459-509)
  • print_colored_debug (66-70)
  • get (356-386)
  • get (439-456)
tensorrt_llm/logger.py (1)
  • warning (132-133)
🪛 Ruff (0.14.4)
tensorrt_llm/llmapi/utils.py

506-506: Do not use bare except

(E722)


506-507: try-except-pass detected, consider logging the exception

(S110)

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  • GitHub Check: Pre-commit Check

Comment on lines +480 to +507
try:
# initialize NVML
import pynvml
pynvml.nvmlInit()

# Get the number of bits per ulong
c_ulong_bits = ctypes.sizeof(ctypes.c_ulong) * 8

# Determine how large our cpu set array from NVML needs to be
cpu_set_size = math.ceil(cpu_count / c_ulong_bits)

# Get the optimal CPU affinity for this device according to the NUMA
# topology
handle = pynvml.nvmlDeviceGetHandleByIndex(device_id)
affinity_masks = pynvml.nvmlDeviceGetCpuAffinity(handle, cpu_set_size)

# Convert CPU masks to python list
cpu_affinity = []
for cpu_id in range(cpu_count):
mask_array_index = cpu_id // c_ulong_bits
mask_bit_index = cpu_id % c_ulong_bits
if affinity_masks[mask_array_index] & (1 << mask_bit_index):
cpu_affinity.append(cpu_id)
finally:
try:
pynvml.nvmlShutdown()
except:
pass # Ignore shutdown errors
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⚠️ Potential issue | 🔴 Critical

Guard NUMA affinity when NVML isn’t available

If pynvml is missing or NVML init fails, the finally block still tries to call pynvml.nvmlShutdown(), but pynvml is undefined in that scenario. The resulting UnboundLocalError bubbles up into BaseWorker._configure_affinity and prevents workers from starting on any host without NVML installed—exactly the environment where we need to fall back to the unconstrained affinity declared at the top of this helper. Please short-circuit when the import or NVML calls fail so we return the default affinity safely.

Apply this diff:

-    try:
-        # initialize NVML
-        import pynvml
-        pynvml.nvmlInit()
+    try:
+        import pynvml
+    except ModuleNotFoundError:
+        return cpu_affinity
+
+    try:
+        pynvml.nvmlInit()
@@
-    finally:
-        try:
-            pynvml.nvmlShutdown()
-        except:
-            pass  # Ignore shutdown errors
+    except pynvml.NVMLError:
+        return cpu_affinity
+    finally:
+        try:
+            pynvml.nvmlShutdown()
+        except pynvml.NVMLError:
+            pass  # Ignore shutdown errors
🧰 Tools
🪛 Ruff (0.14.4)

506-506: Do not use bare except

(E722)


506-507: try-except-pass detected, consider logging the exception

(S110)

Signed-off-by: Dan Hansen <[email protected]>
Co-authored-by: Dan Hansen <[email protected]>
Signed-off-by: Dan Hansen <[email protected]>
@dhansen-nvidia dhansen-nvidia force-pushed the numa_aware_affinity_1.1 branch from 6ed9572 to 99bd4b9 Compare November 13, 2025 01:48
@dhansen-nvidia dhansen-nvidia changed the title [https://nvbugs/5527655][feat] Add NUMA-aware CPU affinity autoconfig… [https://nvbugs/5527655][feat] Cherry-pick https://github.com/NVIDIA/TensorRT-LLM/pull/8805 Nov 13, 2025
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/bot run --disable-fail-fast

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PR_Github #24357 [ run ] triggered by Bot. Commit: 99bd4b9

@nv-guomingz nv-guomingz added the Cherry-pick It's a label that applies to Cherry-pick PR. label Nov 13, 2025
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PR_Github #24357 [ run ] completed with state SUCCESS. Commit: 99bd4b9
/LLM/release-1.1/L0_MergeRequest_PR pipeline #475 completed with status: 'FAILURE'

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/bot run --disable-fail-fast

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/bot run --disable-fail-fast

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PR_Github #24506 [ run ] triggered by Bot. Commit: ad2479b

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PR_Github #24507 [ run ] triggered by Bot. Commit: ad2479b

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PR_Github #24506 [ run ] completed with state ABORTED. Commit: ad2479b

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PR_Github #24507 [ run ] completed with state SUCCESS. Commit: ad2479b
/LLM/release-1.1/L0_MergeRequest_PR pipeline #490 completed with status: 'FAILURE'

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/bot run --disable-fail-fast

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PR_Github #24605 [ run ] triggered by Bot. Commit: ad2479b

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PR_Github #24605 [ run ] completed with state SUCCESS. Commit: ad2479b
/LLM/release-1.1/L0_MergeRequest_PR pipeline #497 completed with status: 'FAILURE'

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/bot run --disable-fail-fast

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PR_Github #25228 [ run ] triggered by Bot. Commit: ad2479b

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PR_Github #25228 [ run ] completed with state SUCCESS. Commit: ad2479b
/LLM/release-1.1/L0_MergeRequest_PR pipeline #513 completed with status: 'FAILURE'

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/bot run --disable-fail-fast

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/bot kill

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PR_Github #25367 [ run ] triggered by Bot. Commit: c93e62c

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PR_Github #25368 [ kill ] triggered by Bot. Commit: c93e62c

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PR_Github #25367 [ run ] completed with state ABORTED. Commit: c93e62c

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PR_Github #25368 [ kill ] completed with state SUCCESS. Commit: c93e62c
Successfully killed previous jobs for commit c93e62c

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/bot run --disable-fail-fast

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PR_Github #25371 [ run ] triggered by Bot. Commit: c93e62c

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PR_Github #25371 [ run ] completed with state SUCCESS. Commit: c93e62c
/LLM/release-1.1/L0_MergeRequest_PR pipeline #525 completed with status: 'FAILURE'

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/bot run --disable-fail-fast

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PR_Github #25768 [ run ] triggered by Bot. Commit: c93e62c

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PR_Github #25768 [ run ] completed with state SUCCESS. Commit: c93e62c
/LLM/release-1.1/L0_MergeRequest_PR pipeline #530 completed with status: 'FAILURE'

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After calibration with Xiaowei/Tao, this PR can affect default CPU affinity logics which can bring perf regression, so should not be merged to 1.1 release.
@dhansen-nvidia can figure out how to improve it in the main branch directly.

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