ollama - 💡(How to fix) Fix CPU bound delays [7 comments, 3 participants]

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ollama/ollama#15025Fetched 2026-04-08 01:21:50
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What is the issue?

During long sessions in opencode, i noticed that the GPU is idle waiting for something, the GPU is idle so there is some CPU process bottleneck, notice the CPU spikes (single threaded work) between GPU spikes.

<img width="1253" height="422" alt="Image" src="https://github.com/user-attachments/assets/90fed92a-25b6-40fa-b9cb-fd145d71494f" /> <img width="1258" height="481" alt="Image" src="https://github.com/user-attachments/assets/e9111484-2e42-4332-b140-d7a9e0469be8" />

GPU: RTX Pro 6000 MaxQ CPU: Intel Core i9-14900k RAM: 64GB DDR5 Model: qwen3.5:122b

Relevant log output

OS

Linux

GPU

Nvidia

CPU

Intel

Ollama version

0.17.5

extent analysis

Fix Plan

The fix involves optimizing CPU-GPU synchronization and potentially leveraging multi-threading for CPU-bound tasks.

  • Step 1: Profile and Identify Bottlenecks
    • Use profiling tools to identify specific CPU-bound tasks causing the bottleneck.
  • Step 2: Implement Multi-Threading for CPU-Bound Tasks
    • Utilize libraries like joblib or concurrent.futures for parallelizing tasks.
    • Example using concurrent.futures:

import concurrent.futures

def cpu_bound_task(data): # Simulate CPU-bound task import time time.sleep(1) return data * 2

def main(): data_list = [1, 2, 3, 4, 5] with concurrent.futures.ThreadPoolExecutor() as executor: results = list(executor.map(cpu_bound_task, data_list)) print(results)

if name == "main": main()

*   **Step 3: Optimize GPU-CPU Synchronization**
    *   Ensure proper synchronization between GPU and CPU tasks using libraries like `cuda` or `cupy`.
    *   Example using `cupy`:
        ```python
import cupy as cp

def gpu_task(data):
    # Simulate GPU task
    return cp.square(data)

def main():
    data = cp.array([1, 2, 3, 4, 5])
    result = gpu_task(data)
    print(result)

if __name__ == "__main__":
    main()

Verification

Verify the fix by monitoring CPU and GPU usage during long sessions and checking for improved performance.

Extra Tips

  • Regularly update dependencies like ollama and cuda to ensure latest optimizations and fixes.
  • Consider using tools like nvprof for detailed GPU profiling and line_profiler for CPU profiling.

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