Log autotune choices and benchmark result to scuba/chrome trace (#159496)

Summary:
Report the kernel choices and benchmark data to better understand how kernels are selected and the performance gap between the best kernel (likely a CUDA kernel) and Triton kernels.

**Example**

Event: mm_template_autotuning
Column: autotune_choices

```json
{
  "num_choices": 52,
  "num_triton_choices": 19,
  "best_kernel": "cutlass_f6c25cf2",
  "best_kernel_desc": "cutlass3x_sm90_tensorop_gemm_f16_f16_f32_void_f16_128x256x64_2x1x1_0_tnn_align8_stream_k_warpspecialized_cooperative_epi_tma swizzle=8",
  "best_time": 0.6283040046691895,
  "best_triton_pos": 26,
  "best_triton_time": 0.6832960247993469,
  "best_triton_kernel": "triton_mm_17",
  "best_triton_kernel_desc": "ACC_TYPE='tl.float32', ALLOW_TF32=False, BLOCK_K=64, BLOCK_M=128, BLOCK_N=128, EVEN_K=True, GROUP_M=8, USE_FAST_ACCUM=False, num_stages=3, num_warps=4, num_consumer_groups=0, num_buffers_warp_spec=0"
}
```

Test Plan:
```
TORCHINDUCTOR_MAX_AUTOTUNE_REPORT_CHOICES_STATS =1 buck2 run //scripts/wychi:test_autotune_mm 2>&1 > /tmp/mylog.txt
```

Rollback Plan:

Differential Revision: D79235037

Pull Request resolved: https://github.com/pytorch/pytorch/pull/159496
Approved by: https://github.com/masnesral

torch/_inductor/select_algorithm.py

@@ -27,7 +27,13 @@ import torch
 import torch._inductor.async_compile  # noqa: F401 required to warm up AsyncCompile pools
 from torch._dynamo.device_interface import get_interface_for_device
 from torch._dynamo.testing import rand_strided
-from torch._dynamo.utils import counters, dynamo_timed, identity, preserve_rng_state
+from torch._dynamo.utils import (
+    counters,
+    dynamo_timed,
+    get_chromium_event_logger,
+    identity,
+    preserve_rng_state,
+)
 from torch._inductor.utils import clear_on_fresh_cache
 from torch.utils._filelock import FileLock
 from torch.utils._ordered_set import OrderedSet
@@ -2339,7 +2345,12 @@ class AlgorithmSelectorCache(PersistentCache):
                 dynamo_compile_column_us="compile_time_autotune_time_us",
                 metadata=_autotune_metadata(input_nodes),
             ):
-                return benchmark(choices, hint_override=hint_override)
+                benchmark_results = benchmark(choices, hint_override=hint_override)
+                if config.max_autotune_report_choices_stats:
+                    _log_autotune_choices_stats(
+                        f"{name}_template_autotuning", benchmark_results
+                    )
+                return benchmark_results
 
         if config.autotune_in_subproc:
             # Initialize the suprocess pool so it will warmup early.
@@ -3396,5 +3407,50 @@ def _autotune_metadata(input_nodes):
     }
 
 
+def _log_autotune_choices_stats(
+    event_name: str, timings: dict[ChoiceCaller, float]
+) -> None:
+    """Helper function to extract autotune metadata from benchmark results."""
+    if not timings:
+        return None
+
+    metadata: dict[str, Union[int, float, str]] = {
+        "num_choices": len(timings),
+        "num_triton_choices": len(
+            [c for c in timings if isinstance(c, TritonTemplateCaller)]
+        ),
+    }
+
+    sorted_choices = sorted(timings, key=timings.__getitem__)
+    best_choice = sorted_choices[0]
+    metadata["best_kernel"] = best_choice.name
+    if best_choice.description:
+        metadata["best_kernel_desc"] = best_choice.description
+    metadata["best_time"] = timings[best_choice]
+
+    best_triton_pos = next(
+        (
+            i
+            for i, choice in enumerate(sorted_choices)
+            if isinstance(choice, TritonTemplateCaller)
+        ),
+        None,
+    )
+    if best_triton_pos is not None:
+        metadata["best_triton_pos"] = best_triton_pos
+        best_triton_kernel = sorted_choices[best_triton_pos]
+        if best_triton_pos != 0:
+            metadata["best_triton_time"] = timings[best_triton_kernel]
+            metadata["best_triton_kernel"] = best_triton_kernel.name
+            if best_triton_kernel.description:
+                metadata["best_triton_kernel_desc"] = best_triton_kernel.description
+
+    payload = json.dumps(metadata)
+    get_chromium_event_logger().add_event_data(
+        event_name, autotune_choices_stats=payload
+    )
+    sys.stderr.write(f"Autotune Choices Stats:\n{payload}\n")
+
+
 # ensure lowering is imported so that `extern_kernels.*` is populated
 from . import lowering  # noqa: F401