[Misc] Fix up attention benchmarks (#33810)

Signed-off-by: Lucas Wilkinson <lwilkins@redhat.com>
Signed-off-by: Matthew Bonanni <mbonanni@redhat.com>
Co-authored-by: Matthew Bonanni <mbonanni@redhat.com>

benchmarks/attention_benchmarks/batch_spec.py

@@ -229,3 +229,40 @@ def get_batch_stats(requests: list[BatchRequest]) -> dict:
             sum(r.kv_len for r in requests) / len(requests) if requests else 0
         ),
     }
+
+
+def get_batch_type(batch_spec: str, spec_decode_threshold: int = 8) -> str:
+    """
+    Classify a batch spec into a type string.
+
+    Args:
+        batch_spec: Batch specification string (e.g., "q2k", "8q1s1k", "2q2k_8q1s1k")
+        spec_decode_threshold: Max q_len to be considered spec-decode vs extend
+
+    Returns:
+        Type string: "prefill", "decode", "spec-decode", "extend", or "mixed (types...)"
+    """
+    requests = parse_batch_spec(batch_spec)
+
+    # Classify each request
+    types_present = set()
+    for req in requests:
+        if req.is_decode:
+            types_present.add("decode")
+        elif req.is_prefill:
+            types_present.add("prefill")
+        elif req.is_extend:
+            # Distinguish spec-decode (small q_len) from extend (chunked prefill)
+            if req.q_len <= spec_decode_threshold:
+                types_present.add("spec-decode")
+            else:
+                types_present.add("extend")
+
+    if len(types_present) == 1:
+        return types_present.pop()
+    elif len(types_present) > 1:
+        # Sort for consistent output
+        sorted_types = sorted(types_present)
+        return f"mixed ({'+'.join(sorted_types)})"
+    else:
+        return "unknown"