API Perf: Replace pydantic per-element validation with C loop validation (#26355)

benchmark/io/bench_input_ids_validator.py

@@ -0,0 +1,67 @@
+"""Microbenchmark: cost of validating `input_ids` during FastAPI body binding.
+
+Compares two validators on a single `input_ids` field:
+- GenerateReqInputPydanticValidator: default pydantic walk (per-element type check)
+- GenerateReqInputCustomValidator: C-loop validator (validate_optional_list_i64_1d_2d)
+
+Usage:
+    python benchmark/io/bench_input_ids_validator.py
+"""
+
+import time
+from dataclasses import dataclass
+from typing import Annotated, List, Optional, Union
+
+from pydantic import PlainValidator, TypeAdapter
+
+from sglang.srt.utils.field_validators import validate_optional_list_i64_1d_2d
+
+
+@dataclass
+class GenerateReqInputPydanticValidator:
+    """Default pydantic — walks every element of input_ids to type-check."""
+
+    input_ids: Optional[Union[List[List[int]], List[int]]] = None
+
+
+@dataclass
+class GenerateReqInputCustomValidator:
+    """C-loop validator via PlainValidator."""
+
+    input_ids: Annotated[
+        Optional[Union[List[List[int]], List[int]]],
+        PlainValidator(validate_optional_list_i64_1d_2d),
+    ] = None
+
+
+_ta_pydantic = TypeAdapter(GenerateReqInputPydanticValidator)
+_ta_custom = TypeAdapter(GenerateReqInputCustomValidator)
+
+
+def _time(fn, n_iter=30):
+    t0 = time.perf_counter()
+    for _ in range(n_iter):
+        fn()
+    return (time.perf_counter() - t0) * 1000 / n_iter
+
+
+def main():
+    print(
+        f"{'n_tokens':>9s} | {'default pydantic (ms)':>22s} | "
+        f"{'rigid i64 validator (ms)':>26s}"
+    )
+    print("-" * 65)
+
+    for n in [1_000, 10_000, 100_000, 1_000_000]:
+        d = {"input_ids": list(range(1, n + 1))}
+
+        p1 = _time(lambda: _ta_pydantic.validate_python(d))
+        p2 = _time(lambda: _ta_custom.validate_python(d))
+
+        print(f"{n:>9d} | {p1:>22.3f} | {p2:>26.3f}")
+
+    print("\nLegend: mean over 30 iters, in ms.")
+
+
+if __name__ == "__main__":
+    main()