[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>

.buildkite/test_areas/benchmarks.yaml

@@ -17,3 +17,14 @@ steps:
   - tests/benchmarks/
   commands:
   - pytest -v -s benchmarks/
+
+- label: Attention Benchmarks Smoke Test (B200)
+  device: b200
+  num_gpus: 2
+  optional: true
+  timeout_in_minutes: 10
+  source_file_dependencies:
+  - benchmarks/attention_benchmarks/
+  - vllm/v1/attention/
+  commands:
+  - python benchmarks/attention_benchmarks/benchmark.py --backends flash flashinfer --batch-specs "8q1s1k" --repeats 1 --warmup-iters 1

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"

benchmarks/attention_benchmarks/common.py

@@ -12,6 +12,7 @@ from typing import Any
 
 import numpy as np
 import torch
+from batch_spec import get_batch_type, parse_batch_spec
 from rich.console import Console
 from rich.table import Table
 
@@ -316,12 +317,14 @@ class ResultsFormatter:
             backends: List of backend names being compared
             compare_to_fastest: Show percentage comparison to fastest
         """
-        # Group by batch spec
+        # Group by batch spec, preserving first-occurrence order
         by_spec = {}
+        specs_order = []
         for r in results:
             spec = r.config.batch_spec
             if spec not in by_spec:
                 by_spec[spec] = {}
+                specs_order.append(spec)
             by_spec[spec][r.config.backend] = r
 
         # Create shortened backend names for display
@@ -337,6 +340,8 @@ class ResultsFormatter:
 
         table = Table(title="Attention Benchmark Results")
         table.add_column("Batch\nSpec", no_wrap=True)
+        table.add_column("Type", no_wrap=True)
+        table.add_column("Batch\nSize", justify="right", no_wrap=True)
 
         multi = len(backends) > 1
         for backend in backends:
@@ -350,12 +355,14 @@ class ResultsFormatter:
                 table.add_column(col_rel, justify="right", no_wrap=False)
 
         # Add rows
-        for spec in sorted(by_spec.keys()):
+        for spec in specs_order:
             spec_results = by_spec[spec]
             times = {b: r.mean_time for b, r in spec_results.items() if r.success}
             best_time = min(times.values()) if times else 0.0
 
-            row = [spec]
+            batch_type = get_batch_type(spec)
+            batch_size = len(parse_batch_spec(spec))
+            row = [spec, batch_type, str(batch_size)]
             for backend in backends:
                 if backend in spec_results:
                     r = spec_results[backend]

benchmarks/attention_benchmarks/configs/standard_attention.yaml

@@ -25,10 +25,18 @@ batch_specs:
   - "4q1k_16q1s2k"     # 4 prefill + 16 decode
   - "2q4k_32q1s1k"     # 2 large prefill + 32 decode
 
-  # Context extension
-  - "q1ks2k"          # 1k query, 2k sequence (chunked prefill)
+  # Speculative decode (q <= 8)
+  - "16q2s1k"         # 16 requests, 2 spec tokens, 1k KV cache
+  - "16q4s1k"         # 16 requests, 4 spec tokens, 1k KV cache
+  - "16q8s1k"         # 16 requests, 8 spec tokens, 1k KV cache
+  - "32q4s2k"         # 32 requests, 4 spec tokens, 2k KV cache
+  - "8q8s4k"          # 8 requests, 8 spec tokens, 4k KV cache
+
+  # Context extension (chunked prefill)
+  - "q1ks2k"          # 1k query, 2k sequence
   - "2q1ks4k"         # 2 requests: 1k query, 4k sequence
 
+# Available backends: flash, triton, flashinfer
 backends:
   - flash
   - triton

benchmarks/attention_benchmarks/runner.py

@@ -8,7 +8,9 @@ This module provides helpers for running standard attention backends
 (FlashAttention, Triton, FlashInfer) with real vLLM integration.
 """
 
+import logging
 import types
+from contextlib import contextmanager
 
 import numpy as np
 import torch
@@ -24,8 +26,13 @@ from vllm.config import (
     ParallelConfig,
     SchedulerConfig,
     VllmConfig,
+    set_current_vllm_config,
+)
+from vllm.v1.attention.backends.utils import (
+    CommonAttentionMetadata,
+    get_kv_cache_layout,
+    set_kv_cache_layout,
 )
-from vllm.v1.attention.backends.utils import CommonAttentionMetadata
 from vllm.v1.kv_cache_interface import FullAttentionSpec
 
 # ============================================================================
@@ -37,22 +44,14 @@ _BACKEND_CONFIG = {
     "flash": {
         "module": "vllm.v1.attention.backends.flash_attn",
         "backend_class": "FlashAttentionBackend",
-        "dtype": torch.float16,
-        "cache_layout": "standard",
-        # ^ [2, num_blocks, block_size, num_kv_heads, head_dim]
     },
     "triton": {
         "module": "vllm.v1.attention.backends.triton_attn",
         "backend_class": "TritonAttentionBackend",
-        "dtype": torch.float32,
-        "cache_layout": "standard",
     },
     "flashinfer": {
         "module": "vllm.v1.attention.backends.flashinfer",
         "backend_class": "FlashInferBackend",
-        "dtype": torch.float16,
-        "cache_layout": "flashinfer",
-        # ^ [num_blocks, 2, block_size, num_kv_heads, head_dim]
     },
 }
 
@@ -66,6 +65,18 @@ def _get_backend_config(backend: str) -> dict:
     return _BACKEND_CONFIG[backend]
 
 
+@contextmanager
+def log_warnings_and_errors_only():
+    """Temporarily set vLLM logger to WARNING level."""
+    logger = logging.getLogger("vllm")
+    old_level = logger.level
+    logger.setLevel(logging.WARNING)
+    try:
+        yield
+    finally:
+        logger.setLevel(old_level)
+
+
 # ============================================================================
 # Metadata Building Helpers
 # ============================================================================
@@ -88,11 +99,7 @@ def _build_common_attn_metadata(
     query_start_loc_cpu = query_start_loc.cpu()
 
     seq_lens = torch.tensor(kv_lens, dtype=torch.int32, device=device)
-    seq_lens_cpu = seq_lens.cpu()
-    max_seq_len = int(seq_lens_cpu.max())
-
-    context_lens = [kv - q for kv, q in zip(kv_lens, q_lens)]
-    num_computed_tokens_cpu = torch.tensor(context_lens, dtype=torch.int32)
+    max_seq_len = int(seq_lens.max().item())
 
     max_blocks = (max(kv_lens) + block_size - 1) // block_size
     num_blocks = batch_size * max_blocks
@@ -107,8 +114,6 @@ def _build_common_attn_metadata(
         query_start_loc=query_start_loc,
         query_start_loc_cpu=query_start_loc_cpu,
         seq_lens=seq_lens,
-        seq_lens_cpu=seq_lens_cpu,
-        num_computed_tokens_cpu=num_computed_tokens_cpu,
         num_reqs=batch_size,
         num_actual_tokens=total_tokens,
         max_query_len=max_query_len,
@@ -121,7 +126,6 @@ def _build_common_attn_metadata(
 
 def _create_vllm_config(
     config: BenchmarkConfig,
-    dtype: torch.dtype,
     max_num_blocks: int,
 ) -> VllmConfig:
     """Create a VllmConfig for benchmarking with mock model methods."""
@@ -129,7 +133,7 @@ def _create_vllm_config(
         model="meta-llama/Meta-Llama-3-8B",
         tokenizer="meta-llama/Meta-Llama-3-8B",
         trust_remote_code=False,
-        dtype=dtype,
+        dtype="auto",  # Use model's native dtype
         seed=0,
         max_model_len=1024,
     )
@@ -198,6 +202,7 @@ def _create_backend_impl(
     backend_cfg: dict,
     config: BenchmarkConfig,
     device: torch.device,
+    dtype: torch.dtype,
 ):
     """Create backend implementation instance."""
     import importlib
@@ -206,7 +211,6 @@ def _create_backend_impl(
     backend_class = getattr(backend_module, backend_cfg["backend_class"])
 
     scale = get_attention_scale(config.head_dim)
-    dtype = backend_cfg["dtype"]
 
     impl = backend_class.get_impl_cls()(
         num_heads=config.num_q_heads,
@@ -227,7 +231,7 @@ def _create_backend_impl(
 
     layer = MockLayer(device, kv_cache_spec=kv_cache_spec)
 
-    return backend_class, impl, layer, dtype
+    return backend_class, impl, layer
 
 
 def _create_metadata_builder(
@@ -235,11 +239,44 @@ def _create_metadata_builder(
     kv_cache_spec: FullAttentionSpec,
     vllm_config: VllmConfig,
     device: torch.device,
+    backend_name: str = "",
 ):
     """Create metadata builder instance."""
-    return backend_class.get_builder_cls()(
+    layer_names = ["layer_0"]
+    builder_cls = backend_class.get_builder_cls()
+
+    # Flashinfer needs get_per_layer_parameters mocked since we don't have
+    # real model layers registered
+    if backend_name == "flashinfer":
+        import unittest.mock
+
+        from vllm.v1.attention.backends.utils import PerLayerParameters
+
+        def mock_get_per_layer_parameters(vllm_config, layer_names, impl_cls):
+            head_size = vllm_config.model_config.get_head_size()
+            return {
+                layer_name: PerLayerParameters(
+                    window_left=-1,  # No sliding window
+                    logits_soft_cap=0.0,  # No soft cap
+                    sm_scale=1.0 / (head_size**0.5),  # Standard scale
+                )
+                for layer_name in layer_names
+            }
+
+        with unittest.mock.patch(
+            "vllm.v1.attention.backends.flashinfer.get_per_layer_parameters",
+            mock_get_per_layer_parameters,
+        ):
+            return builder_cls(
                 kv_cache_spec=kv_cache_spec,
-        layer_names=["layer_0"],
+                layer_names=layer_names,
+                vllm_config=vllm_config,
+                device=device,
+            )
+
+    return builder_cls(
+        kv_cache_spec=kv_cache_spec,
+        layer_names=layer_names,
         vllm_config=vllm_config,
         device=device,
     )
@@ -281,39 +318,44 @@ def _create_input_tensors(
 def _create_kv_cache(
     config: BenchmarkConfig,
     max_num_blocks: int,
-    cache_layout: str,
+    backend_class,
     device: torch.device,
     dtype: torch.dtype,
 ) -> list:
-    """Create KV cache tensors for all layers."""
-    if cache_layout == "flashinfer":
-        # FlashInfer layout: [num_blocks, 2, block_size, num_kv_heads, head_dim]
-        cache_list = [
-            torch.zeros(
-                max_num_blocks,
-                2,
-                config.block_size,
-                config.num_kv_heads,
-                config.head_dim,
-                device=device,
-                dtype=dtype,
-            )
-            for _ in range(config.num_layers)
-        ]
-    else:
-        # Standard layout: [2, num_blocks, block_size, num_kv_heads, head_dim]
-        cache_list = [
-            torch.zeros(
-                2,
-                max_num_blocks,
-                config.block_size,
-                config.num_kv_heads,
-                config.head_dim,
-                device=device,
-                dtype=dtype,
+    """Create KV cache tensors for all layers using the backend's methods.
+
+    Uses the backend's get_kv_cache_shape() and get_kv_cache_stride_order()
+    to create the cache with the correct shape and memory layout.
+    """
+    # Get the logical shape from the backend
+    cache_shape = backend_class.get_kv_cache_shape(
+        num_blocks=max_num_blocks,
+        block_size=config.block_size,
+        num_kv_heads=config.num_kv_heads,
+        head_size=config.head_dim,
     )
-            for _ in range(config.num_layers)
-        ]
+
+    # Get the stride order for custom memory layout
+    try:
+        stride_order = backend_class.get_kv_cache_stride_order()
+        assert len(stride_order) == len(cache_shape)
+    except (AttributeError, NotImplementedError):
+        stride_order = tuple(range(len(cache_shape)))
+
+    # Permute shape to physical layout order
+    physical_shape = tuple(cache_shape[i] for i in stride_order)
+
+    # Compute inverse permutation to get back to logical view
+    inv_order = [stride_order.index(i) for i in range(len(stride_order))]
+
+    cache_list = []
+    for _ in range(config.num_layers):
+        # Allocate in physical layout order (contiguous in memory)
+        cache = torch.zeros(*physical_shape, device=device, dtype=dtype)
+        # Permute to logical view
+        cache = cache.permute(*inv_order)
+        cache_list.append(cache)
+
     return cache_list
 
 
@@ -418,13 +460,32 @@ def run_attention_benchmark(config: BenchmarkConfig) -> BenchmarkResult:
     kv_lens = [r.kv_len for r in requests]
     total_q = sum(q_lens)
     max_kv = max(kv_lens)
+    batch_size = len(q_lens)
+
+    # Calculate total blocks needed: batch_size * max_blocks_per_request
+    max_blocks_per_request = (max_kv + config.block_size - 1) // config.block_size
+    max_num_blocks = batch_size * max_blocks_per_request
 
-    max_num_blocks = (max_kv + config.block_size - 1) // config.block_size
+    # Suppress vLLM logs during setup to reduce spam
+    with log_warnings_and_errors_only():
+        # Create vllm_config first - uses model's native dtype via "auto"
+        vllm_config = _create_vllm_config(config, max_num_blocks)
+        dtype = vllm_config.model_config.dtype
 
-    backend_class, impl, layer, dtype = _create_backend_impl(
-        backend_cfg, config, device
+        # Wrap everything in set_current_vllm_config context
+        # This is required for backends like flashinfer that need global config
+        with set_current_vllm_config(vllm_config):
+            backend_class, impl, layer = _create_backend_impl(
+                backend_cfg, config, device, dtype
             )
 
+            # Set KV cache layout if the backend requires a specific one
+            # (e.g., FlashInfer requires HND on SM100/Blackwell for TRTLLM attention)
+            required_layout = backend_class.get_required_kv_cache_layout()
+            if required_layout is not None:
+                set_kv_cache_layout(required_layout)
+                get_kv_cache_layout.cache_clear()
+
             common_metadata = _build_common_attn_metadata(
                 q_lens, kv_lens, config.block_size, device
             )
@@ -436,10 +497,8 @@ def run_attention_benchmark(config: BenchmarkConfig) -> BenchmarkResult:
                 dtype=dtype,
             )
 
-    vllm_config = _create_vllm_config(config, dtype, max_num_blocks)
-
             builder = _create_metadata_builder(
-        backend_class, kv_cache_spec, vllm_config, device
+                backend_class, kv_cache_spec, vllm_config, device, config.backend
             )
 
             attn_metadata = builder.build(
@@ -447,10 +506,12 @@ def run_attention_benchmark(config: BenchmarkConfig) -> BenchmarkResult:
                 common_attn_metadata=common_metadata,
             )
 
-    q_list, k_list, v_list = _create_input_tensors(config, total_q, device, dtype)
+            q_list, k_list, v_list = _create_input_tensors(
+                config, total_q, device, dtype
+            )
 
             cache_list = _create_kv_cache(
-        config, max_num_blocks, backend_cfg["cache_layout"], device, dtype
+                config, max_num_blocks, backend_class, device, dtype
             )
 
             times, mem_stats = _run_single_benchmark(