[test] add ut and bm for get_last_loc (#6746)

benchmark/kernels/scheduler_batch/benchmark_get_last_loc_triton.py

+import os
+
+import torch
+import triton
+import triton.language as tl
+
+
+@torch.compile(dynamic=True)
+def get_last_loc_torch(
+    req_to_token: torch.Tensor,
+    req_pool_indices_tensor: torch.Tensor,
+    prefix_lens_tensor: torch.Tensor,
+) -> torch.Tensor:
+    return torch.where(
+        prefix_lens_tensor > 0,
+        req_to_token[req_pool_indices_tensor, prefix_lens_tensor - 1],
+        torch.full_like(prefix_lens_tensor, -1),
+    )
+
+
+@triton.jit
+def get_last_loc_kernel(
+    req_to_token,
+    req_pool_indices_tensor,
+    prefix_lens_tensor,
+    result,
+    num_tokens,
+    req_to_token_stride,
+    BLOCK_SIZE: tl.constexpr,
+):
+    pid = tl.program_id(0)
+    offset = tl.arange(0, BLOCK_SIZE) + pid * BLOCK_SIZE
+    mask = offset < num_tokens
+
+    prefix_lens = tl.load(prefix_lens_tensor + offset, mask=mask, other=0)
+    req_pool_indices = tl.load(req_pool_indices_tensor + offset, mask=mask, other=0)
+
+    token_mask = prefix_lens > 0
+    token_index = req_pool_indices * req_to_token_stride + (prefix_lens - 1)
+    tokens = tl.load(req_to_token + token_index, mask=token_mask, other=-1)
+
+    tl.store(result + offset, tokens, mask=mask)
+
+
+def get_last_loc_triton(
+    req_to_token: torch.Tensor,
+    req_pool_indices_tensor: torch.Tensor,
+    prefix_lens_tensor: torch.Tensor,
+) -> torch.Tensor:
+    BLOCK_SIZE = 256
+    num_tokens = prefix_lens_tensor.shape[0]
+    result = torch.empty_like(prefix_lens_tensor)
+    grid = (triton.cdiv(num_tokens, BLOCK_SIZE),)
+
+    get_last_loc_kernel[grid](
+        req_to_token,
+        req_pool_indices_tensor,
+        prefix_lens_tensor,
+        result,
+        num_tokens,
+        req_to_token.stride(0),
+        BLOCK_SIZE,
+    )
+    return result
+
+
+def test_get_last_loc():
+    max_batch = 4097
+    max_context_len = 6148
+    batch_size = 20
+
+    # Initialize input tensors
+    req_to_token = torch.zeros(
+        (max_batch, max_context_len), dtype=torch.int32, device="cuda"
+    )
+    req_pool_indices = torch.arange(batch_size, dtype=torch.int64, device="cuda")
+    pre_lens = torch.randint(
+        -max_context_len // 2,
+        max_context_len,
+        (batch_size,),
+        dtype=torch.int64,
+        device="cuda",
+    )
+
+    last_loc_res = get_last_loc_triton(req_to_token, req_pool_indices, pre_lens)
+    last_loc_ref = get_last_loc_torch(req_to_token, req_pool_indices, pre_lens)
+
+    # Compare results
+    torch.testing.assert_close(last_loc_res, last_loc_ref)
+
+
+def get_benchmark():
+    batch_sizes = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024]
+
+    @triton.testing.perf_report(
+        triton.testing.Benchmark(
+            x_names=["batch_size"],
+            x_vals=batch_sizes,
+            line_arg="provider",
+            line_vals=["reference", "triton"],
+            line_names=["PyTorch", "Triton"],
+            styles=[("blue", "-"), ("green", "-")],
+            ylabel="us",
+            plot_name="get-last-loc-performance",
+            args={},
+        )
+    )
+    def benchmark(batch_size, provider):
+        max_batch = 2048
+        max_context_len = 16384
+
+        req_to_token = torch.zeros(
+            (max_batch, max_context_len), dtype=torch.int32, device="cuda"
+        )
+        req_pool_indices = torch.arange(batch_size, dtype=torch.int64, device="cuda")
+        pre_lens = torch.randint(
+            -max_context_len // 2,
+            max_context_len,
+            (batch_size,),
+            dtype=torch.int64,
+            device="cuda",
+        )
+
+        quantiles = [0.5, 0.2, 0.8]
+
+        if provider == "reference":
+            ms, min_ms, max_ms = triton.testing.do_bench(
+                lambda: get_last_loc_torch(req_to_token, req_pool_indices, pre_lens),
+                quantiles=quantiles,
+            )
+        elif provider == "triton":
+            ms, min_ms, max_ms = triton.testing.do_bench(
+                lambda: get_last_loc_triton(req_to_token, req_pool_indices, pre_lens),
+                quantiles=quantiles,
+            )
+
+        return 1000 * ms, 1000 * max_ms, 1000 * min_ms
+
+    return benchmark
+
+
+def run_benchmark(save_path: str = "./configs/benchmark_ops/get_last_loc/"):
+    """Run benchmark and save results"""
+
+    # Ensure save path exists
+    os.makedirs(save_path, exist_ok=True)
+
+    # Run correctness test
+    test_get_last_loc()
+    print("Correctness test passed!")
+
+    # Run performance test
+    benchmark = get_benchmark()
+    benchmark.run(print_data=True, save_path=save_path)
+
+
+if __name__ == "__main__":
+    import argparse
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--save_path",
+        type=str,
+        default="./configs/benchmark_ops/get_last_loc/",
+        help="Path to save benchmark results",
+    )
+    args = parser.parse_args()
+
+    run_benchmark(args.save_path)