fix(rocm): remove workaround causing invalid argument on Qwen3.5 with TP=2

[aaab8b]

This PR removes a ROCm workaround in cumem_allocator.cpp. Keeping this code causes an invalid argument error during wake_up for the Qwen3.5 model when running with TP=2 on ROCm platforms.

[claude]

Claude Code Review

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[mergify]

Hi @aaab8b, the pre-commit checks have failed. Please run:

uv pip install pre-commit>=4.5.1
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pre-commit run --all-files

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# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10

[gemini-code-assist]

Code Review

This pull request removes a ROCm-specific workaround in csrc/cumem_allocator.cpp that cycled virtual address reservations to force physical VRAM release. I have no feedback to provide.

[aaab8b]

using this script and rocm can reproduce this problem:
import torch
from vllm import LLM

if name == 'main':
llm = LLM(model="Qwen/Qwen3.5-4B",
enable_sleep_mode=True,
tensor_parallel_size=2)

def run_inference(prompt):
    outputs = llm.generate(prompt)
    for output in outputs:
        print(f"Prompt: {output.prompt!r}, Generated: {output.outputs[0].text[:60]!r}")

print("\n===== Round 1 =====")
run_inference("San Francisco is")

print("\n===== Sleep (level 1, TP=2) =====")
llm.sleep(level=1)
torch.cuda.empty_cache()

for i in range(2):
    free, total = torch.cuda.mem_get_info(i)
    print(f"  GPU {i}: free={free/1024**3:.2f} GiB / total={total/1024**3:.1f} GiB")

print("\n===== Allocate 90% VRAM on GPU 0 and 1 =====")
for i in range(2):
    free, total = torch.cuda.mem_get_info(i)
    alloc_bytes = int(total * 0.9)
    try:
        t = torch.empty(alloc_bytes, dtype=torch.uint8, device=f"cuda:{i}")
        print(f"  GPU {i}: allocated {alloc_bytes/1024**3:.2f} GiB ✓")
        del t
        torch.cuda.empty_cache()
    except torch.cuda.OutOfMemoryError:
        print(f"  GPU {i}: FAILED (free={free/1024**3:.2f} GiB) ✗")

print("\n===== Wake up =====")
llm.wake_up()
run_inference("Paris is")

[tjtanaa]

LGTM