Add vLLM v0.18.1 source tree with KV transfer abort fix

third_party/vllm/ now tracked in git for direct patch management.
Based on vLLM v0.18.1 release with one patch applied:

  vllm/v1/core/sched/scheduler.py:
    Replace fatal assert with graceful skip when KV transfer callback
    arrives for an already-aborted request during PD disaggregated serving.

Future vLLM modifications should be made directly in third_party/vllm/
and committed normally. The patches/ directory is kept as documentation
of what changed from upstream.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

third_party/vllm/benchmarks/kernels/benchmark_fused_topk.py

@@ -0,0 +1,99 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import itertools
+
+import torch
+
+from vllm.model_executor.layers.fused_moe.router.fused_topk_router import fused_topk
+from vllm.triton_utils import triton
+from vllm.utils.argparse_utils import FlexibleArgumentParser
+
+num_tokens_range = [2**i for i in range(0, 8, 2)]
+num_experts_range = [16, 32, 64, 128, 256, 512]
+topk_range = [3, 4]
+configs = list(itertools.product(num_tokens_range, num_experts_range, topk_range))
+
+
+def torch_topk(
+    gating_output: torch.Tensor,
+    topk: int,
+    renormalize: bool,
+    scoring_func: str = "softmax",
+):
+    if scoring_func == "softmax":
+        scores = torch.softmax(gating_output.float(), dim=-1)
+    else:
+        scores = torch.sigmoid(gating_output.float())
+    topk_weights, topk_ids = torch.topk(scores, k=topk, dim=-1)
+
+    if renormalize:
+        topk_weights = topk_weights / topk_weights.sum(dim=-1, keepdim=True)
+
+    return topk_weights, topk_ids
+
+
+def get_benchmark(scoring_func):
+    @triton.testing.perf_report(
+        triton.testing.Benchmark(
+            x_names=["num_tokens", "num_experts", "topk"],
+            x_vals=[list(_) for _ in configs],
+            line_arg="provider",
+            line_vals=["torch", "vllm"],
+            line_names=["Torch", "vLLM"],
+            styles=[("blue", "-"), ("red", "-")],
+            ylabel="us",
+            plot_name=f"fused-topk-perf-{scoring_func}",
+            args={},
+        )
+    )
+    def benchmark(num_tokens, num_experts, topk, provider):
+        dtype = torch.bfloat16
+        hidden_size = 1024
+        renormalize = True
+        hidden_states = torch.randn(
+            (num_tokens, hidden_size), dtype=dtype, device="cuda"
+        )
+        gating_output = torch.randn(
+            (num_tokens, num_experts), dtype=dtype, device="cuda"
+        )
+
+        quantiles = [0.5, 0.2, 0.8]
+
+        if provider == "torch":
+            ms, min_ms, max_ms = triton.testing.do_bench(
+                lambda: torch_topk(
+                    gating_output=gating_output,
+                    topk=topk,
+                    renormalize=renormalize,
+                    scoring_func=scoring_func,
+                ),
+                quantiles=quantiles,
+            )
+        else:
+            ms, min_ms, max_ms = triton.testing.do_bench(
+                lambda: fused_topk(
+                    hidden_states=hidden_states,
+                    gating_output=gating_output,
+                    topk=topk,
+                    renormalize=renormalize,
+                    scoring_func=scoring_func,
+                ),
+                quantiles=quantiles,
+            )
+
+        return 1000 * ms, 1000 * max_ms, 1000 * min_ms
+
+    return benchmark
+
+
+if __name__ == "__main__":
+    parser = FlexibleArgumentParser(description="Benchmark the MoE topk kernel.")
+    parser.add_argument("--scoring-func", type=str, default="softmax")
+    parser.add_argument("--save-path", type=str, default="./configs/fused_topk/")
+    args = parser.parse_args()
+
+    # Get the benchmark function
+    benchmark = get_benchmark(args.scoring_func)
+    # Run performance benchmark
+    benchmark.run(print_data=True, save_path=args.save_path)