[NVIDIA] Support Flashinfer TRTLLM FP8-q/kv/out Attention Kernel (vllm-project#21716)

Signed-off-by: elvischenv <[email protected]>
Co-authored-by: Michael Goin <[email protected]>
Co-authored-by: Luka Govedič <[email protected]>

Author: 3 people

.buildkite/test-pipeline.yaml

@@ -631,6 +631,7 @@ steps:
   - vllm/model_executor/layers/fused_moe/flashinfer_cutlass_prepare_finalize.py
   - vllm/v1/attention/backends/flashinfer.py
   - vllm/compilation/fusion.py
+  - vllm/compilation/fusion_attn.py
   commands:
     - nvidia-smi
     - python3 examples/offline_inference/basic/chat.py
@@ -647,6 +648,7 @@ steps:
     - pytest -v -s tests/kernels/moe/test_nvfp4_moe.py
     # Fusion
     - pytest -v -s tests/compile/test_fusion_all_reduce.py
+    - pytest -v -s tests/compile/test_fusion_attn.py::test_attention_quant_pattern
 
 #####  1 GPU test  #####
 #####  multi gpus test  #####

benchmarks/kernels/benchmark_trtllm_decode_attention.py

@@ -3,16 +3,14 @@
 
 import csv
 import os
-import random
 from datetime import datetime
+from typing import Optional
 
 import flashinfer
 import torch
 
 FLOAT32_BYTES = torch.finfo(torch.float).bits // 8
-
-# KV Cache Layout for TRT-LLM
-# kv_cache_shape = (num_blocks, 2, num_kv_heads, page_size, head_dim)
+FP8_DTYPE = torch.float8_e4m3fn
 
 
 def to_float8(x, dtype=torch.float8_e4m3fn):
@@ -26,149 +24,168 @@ def to_float8(x, dtype=torch.float8_e4m3fn):
 
 @torch.no_grad()
 def benchmark_decode(
-    num_seqs,
-    max_seq_len,
-    page_size=16,
-    dtype=torch.bfloat16,
-    kv_layout="HND",
-    num_kv_heads=8,
-    kv_cache_dtype="auto",
-    head_dim=128,
-    warmup=10,
-    trials=20,
+    dtype: torch.dtype,
+    quant_dtypes: tuple[
+        Optional[torch.dtype], Optional[torch.dtype], Optional[torch.dtype]
+    ],
+    batch_size: int,
+    max_seq_len: int,
+    num_heads: tuple[int, int] = (64, 8),
+    head_size: int = 128,
+    kv_layout: str = "HND",
+    block_size: int = 16,
+    warmup: int = 10,
+    trials: int = 20,
 ):
     torch.set_default_device("cuda")
-    device = "cuda"
     torch.manual_seed(0)
 
-    HEAD_GRP_SIZE = 8
-    MAX_SEQ_LEN = max_seq_len
-
-    # large number to reduce kv_cache reuse
-    NUM_BLOCKS = int(256000 / page_size)
-
-    workspace_buffer = torch.empty(1024 * 1024 * 1024, dtype=torch.int8, device=device)
+    q_quant_dtype, kv_quant_dtype, o_quant_dtype = quant_dtypes
+    q_quant_dtype = q_quant_dtype or dtype
+    kv_quant_dtype = kv_quant_dtype or dtype
+    o_quant_dtype = o_quant_dtype or dtype
 
-    # For decode, batch_size is num_decode_token
-    num_qo_heads = num_kv_heads * HEAD_GRP_SIZE
-    sm_scale = float(1.0 / (head_dim**0.5))
-    q = torch.randn(num_seqs, num_qo_heads, head_dim, device=device, dtype=dtype)
-    kv_lens = [random.randint(1, MAX_SEQ_LEN) for _ in range(num_seqs)]
+    num_qo_heads, num_kv_heads = num_heads
+    assert num_qo_heads % num_kv_heads == 0
 
-    max_kv_len = max(kv_lens)
-    kv_lens_tensor = torch.tensor(kv_lens, dtype=torch.int, device=device)
-    max_num_blocks_per_seq = (max_kv_len + page_size - 1) // page_size
+    sm_scale = float(1.0 / (head_size**0.5))
 
+    # large number to reduce kv_cache reuse
+    NUM_BLOCKS = int(256000 / block_size)
+
+    kv_cache_shape = None
+    if kv_layout == "NHD":
+        kv_cache_shape = (NUM_BLOCKS, 2, block_size, num_kv_heads, head_size)
+    elif kv_layout == "HND":
+        kv_cache_shape = (NUM_BLOCKS, 2, num_kv_heads, block_size, head_size)
+    else:
+        raise ValueError(f"Invalid kv_layout: {kv_layout}")
+
+    query = torch.randn(batch_size, num_qo_heads, head_size, dtype=dtype)
+    if q_quant_dtype == FP8_DTYPE:
+        query, q_scale = to_float8(query)
+        ref_query = query.to(dtype) * q_scale
+    else:
+        q_scale = 1.0
+        ref_query = query
+
+    kv_lens = torch.randint(1, max_seq_len, (batch_size,), dtype=torch.int32)
+    kv_lens[-1] = max_seq_len
+
+    seq_lens = kv_lens
+    max_seq_len = torch.max(seq_lens).item()
+
+    kv_cache = torch.randn(kv_cache_shape, dtype=dtype)
+    if kv_quant_dtype == FP8_DTYPE:
+        kv_cache, kv_scale = to_float8(kv_cache)
+        ref_kv_cache = kv_cache.to(dtype) * kv_scale
+    else:
+        kv_scale = 1.0
+        ref_kv_cache = kv_cache
+    k_scale = v_scale = kv_scale
+
+    max_num_blocks_per_seq = (max_seq_len + block_size - 1) // block_size
     block_tables = torch.randint(
-        0, NUM_BLOCKS, (num_seqs, max_num_blocks_per_seq), dtype=torch.int32
+        0, NUM_BLOCKS, (batch_size, max_num_blocks_per_seq), dtype=torch.int32
     )
-
-    kv_cache_shape = (NUM_BLOCKS, 2, num_kv_heads, page_size, head_dim)
-    kv_cache = torch.randn(size=kv_cache_shape, device=device, dtype=dtype)
-    k_scale = v_scale = 1.0
-
-    if kv_cache_dtype.startswith("fp8"):
-        kv_cache, _ = to_float8(kv_cache)
-
-    output_trtllm = torch.empty(q.shape, dtype=dtype)
-
-    # Benchmark TRT decode
-    def trt_decode():
-        return flashinfer.decode.trtllm_batch_decode_with_kv_cache(
-            q,
-            kv_cache,
-            workspace_buffer,
-            block_tables,
-            kv_lens_tensor,
-            max_kv_len,
-            bmm1_scale=k_scale * sm_scale,
-            bmm2_scale=v_scale,
-            out=output_trtllm,
-        )
-
-    def time_fn(fn, warmup=10, trials=20):
-        torch.cuda.synchronize()
-        start = torch.cuda.Event(enable_timing=True)
-        end = torch.cuda.Event(enable_timing=True)
-        times = []
-        for i in range(warmup):
-            fn()
-        for i in range(trials):
-            start.record()
-            fn()
-            end.record()
-            torch.cuda.synchronize()
-            times.append(start.elapsed_time(end))  # ms
-        return sum(times) / len(times), torch.std(torch.tensor(times))
-
-    # TRT Decode
-    trt_mean, trt_std = time_fn(trt_decode)
-
     kv_indptr = [0]
     kv_indices = []
     kv_last_page_lens = []
-    for i in range(num_seqs):
-        seq_len = kv_lens[i]
+    for i in range(batch_size):
+        seq_len = seq_lens[i]
         assert seq_len > 0
-        num_blocks = (seq_len + page_size - 1) // page_size
+        num_blocks = (seq_len + block_size - 1) // block_size
         kv_indices.extend(block_tables[i, :num_blocks])
         kv_indptr.append(kv_indptr[-1] + num_blocks)
-        kv_last_page_len = seq_len % page_size
+        kv_last_page_len = seq_len % block_size
         if kv_last_page_len == 0:
-            kv_last_page_len = page_size
+            kv_last_page_len = block_size
         kv_last_page_lens.append(kv_last_page_len)
 
     kv_indptr = torch.tensor(kv_indptr, dtype=torch.int32)
     kv_indices = torch.tensor(kv_indices, dtype=torch.int32)
     kv_last_page_lens = torch.tensor(kv_last_page_lens, dtype=torch.int32)
-
-    output_baseline = torch.empty(q.shape, dtype=dtype)
+    workspace_buffer = torch.zeros(1024 * 1024 * 1024, dtype=torch.int8)
 
     wrapper = flashinfer.BatchDecodeWithPagedKVCacheWrapper(
         workspace_buffer,
         kv_layout,
         use_tensor_cores=((num_qo_heads // num_kv_heads) > 4),
     )
-
     wrapper.plan(
         kv_indptr,
         kv_indices,
         kv_last_page_lens,
         num_qo_heads,
         num_kv_heads,
-        head_dim,
-        page_size,
+        head_size,
+        block_size,
         "NONE",
+        sm_scale=sm_scale,
         q_data_type=dtype,
-        kv_data_type=torch.float8_e4m3fn if kv_cache_dtype.startswith("fp8") else dtype,
+        kv_data_type=dtype,
     )
 
+    def time_fn(fn, warmup=10, trials=20):
+        torch.cuda.synchronize()
+        start = torch.cuda.Event(enable_timing=True)
+        end = torch.cuda.Event(enable_timing=True)
+        times = []
+        for i in range(warmup):
+            fn()
+        for i in range(trials):
+            start.record()
+            fn()
+            end.record()
+            torch.cuda.synchronize()
+            times.append(start.elapsed_time(end))  # ms
+        return sum(times) / len(times), torch.std(torch.tensor(times))
+
+    o_scale = 1.0
+    output_baseline = torch.empty(ref_query.shape, dtype=dtype)
+    output_trtllm = torch.empty(query.shape, dtype=o_quant_dtype)
+
     def baseline_decode():
-        return wrapper.run(q, kv_cache, sm_scale, k_scale, v_scale, output_baseline)
+        return wrapper.run(ref_query, ref_kv_cache, out=output_baseline)
+
+    def trtllm_decode():
+        return flashinfer.decode.trtllm_batch_decode_with_kv_cache(
+            query=query,
+            kv_cache=kv_cache,
+            workspace_buffer=workspace_buffer,
+            block_tables=block_tables,
+            seq_lens=seq_lens,
+            max_seq_len=max_seq_len,
+            bmm1_scale=q_scale * k_scale * sm_scale,
+            bmm2_scale=v_scale / o_scale,
+            out=output_trtllm,
+        )
 
     baseline_mean, baseline_std = time_fn(baseline_decode)
+    trtllm_mean, trtllm_std = time_fn(trtllm_decode)
 
     # Calculate percentage speedup (positive means TRT is faster)
-    speedup_percent = (baseline_mean - trt_mean) / baseline_mean
+    speedup_percent = (baseline_mean - trtllm_mean) / baseline_mean
 
     print(
-        f"\t{num_seqs}\t{max_seq_len}\t{trt_mean:.3f}\t{trt_std.item():.3f}"
+        f"\t{batch_size}\t{max_seq_len}\t{trtllm_mean:.3f}\t{trtllm_std.item():.3f}"
         f"\t{baseline_mean:.3f}\t{baseline_std.item():.3f}\t{speedup_percent:.3f}"
     )
 
     # Return results for CSV writing
     return {
-        "num_seqs": num_seqs,
-        "trt_mean": trt_mean,
-        "trt_std": trt_std.item(),
+        "batch_size": batch_size,
+        "trtllm_mean": trtllm_mean,
+        "trtllm_std": trtllm_std.item(),
         "baseline_mean": baseline_mean,
         "baseline_std": baseline_std.item(),
         "speedup_percent": speedup_percent,
-        "q_dtype": str(dtype),
-        "kv_cache_dtype": kv_cache_dtype,
-        "page_size": page_size,
+        "q_dtype": str(q_quant_dtype),
+        "kv_cache_dtype": str(kv_quant_dtype),
+        "output_dtype": str(o_quant_dtype),
+        "block_size": block_size,
         "num_kv_heads": num_kv_heads,
-        "head_dim": head_dim,
+        "head_size": head_size,
         "max_seq_len": max_seq_len,
     }
 
@@ -180,17 +197,18 @@ def write_results_to_csv(results, filename=None):
         filename = f"flashinfer_trtllm_benchmark_{timestamp}.csv"
 
     fieldnames = [
-        "num_seqs",
-        "trt_mean",
-        "trt_std",
+        "batch_size",
+        "trtllm_mean",
+        "trtllm_std",
         "baseline_mean",
         "baseline_std",
         "speedup_percent",
         "q_dtype",
         "kv_cache_dtype",
-        "page_size",
+        "output_dtype",
+        "block_size",
         "num_kv_heads",
-        "head_dim",
+        "head_size",
         "max_seq_len",
     ]
 
@@ -209,45 +227,42 @@ def write_results_to_csv(results, filename=None):
 
 
 if __name__ == "__main__":
-    num_seqs = [1, 4, 8, 16, 32, 64, 128, 256]
+    batch_sizes = [1, 4, 8, 16, 32, 64, 128, 256]
     max_seq_lens = [1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072]
     all_results = []
 
-    print(
-        "Running benchmark for q_dtype = bfloat16, kv_cache_dtype: bfloat16, "
-        "output_dtype: bfloat16"
-    )
-    print(
-        "\tnum_seqs\tmax_seq_len\ttrt_mean\ttrt_std\tbaseline_mean\t"
-        "baseline_std\tspeedup_percent"
-    )
-    for max_seq_len in max_seq_lens:
-        for bs in num_seqs:
-            result = benchmark_decode(
-                bs,
-                max_seq_len,
-                dtype=torch.bfloat16,
-                kv_cache_dtype="auto",
-            )
-            all_results.append(result)
+    dtype = torch.bfloat16
+    quant_dtypes = [
+        # (q_quant_dtype, kv_quant_dtype, o_quant_dtype)
+        (None, None, None),
+        (None, FP8_DTYPE, None),
+        (FP8_DTYPE, FP8_DTYPE, FP8_DTYPE),
+    ]
 
-    print(
-        "Running benchmark for q_dtype = bfloat16, kv_cache_dtype: fp8, "
-        "output_dtype: bfloat16"
-    )
-    print(
-        "\tnum_seqs\tmax_seq_len\ttrt_mean\ttrt_std\tbaseline_mean\t"
-        "baseline_std\tspeedup_percent"
-    )
-    for max_seq_len in max_seq_lens:
-        for bs in num_seqs:
-            result = benchmark_decode(
-                bs,
-                max_seq_len,
-                dtype=torch.bfloat16,
-                kv_cache_dtype="fp8",
-            )
-            all_results.append(result)
+    for quant_dtype in quant_dtypes:
+        q_quant_dtype, kv_quant_dtype, o_quant_dtype = quant_dtype
+        q_quant_dtype = q_quant_dtype or dtype
+        kv_quant_dtype = kv_quant_dtype or dtype
+        o_quant_dtype = o_quant_dtype or dtype
+
+        print(
+            f"Running benchmark for q_dtype = {q_quant_dtype}, "
+            f"kv_cache_dtype: {kv_quant_dtype}, "
+            f"output_dtype: {o_quant_dtype}"
+        )
+        print(
+            "\tbatch_size\tmax_seq_len\ttrtllm_mean\ttrtllm_std\tbaseline_mean\t"
+            "baseline_std\tspeedup_percent"
+        )
+        for max_seq_len in max_seq_lens:
+            for bs in batch_sizes:
+                result = benchmark_decode(
+                    dtype=dtype,
+                    quant_dtypes=quant_dtype,
+                    batch_size=bs,
+                    max_seq_len=max_seq_len,
+                )
+                all_results.append(result)
 
     # Write all results to CSV
     write_results_to_csv(all_results)