[AMD] Add fused all-reduce RMSNorm per-group quant for Qwen3.5 FP8 (#24651)

Co-authored-by: jacky.cheng <yichiche@amd.com>
Co-authored-by: yctseng0211 <yctseng@amd.com>
Co-authored-by: HAI <hixiao@gmail.com>
This commit is contained in:
Hubert Lu
2026-07-22 07:33:03 -07:00
committed by GitHub
co-authored by jacky.cheng yctseng0211 HAI
parent b855efd9e6
commit e8e765b9d6
9 changed files with 1192 additions and 8 deletions
@@ -0,0 +1,540 @@
"""
Benchmark fused AllReduce + RMSNorm + per-group FP8 quant on AMD with
correctness checks.
This script targets the three op paths used by SGLang on ROCm/aiter for
Qwen3.5-FP8 style models:
1. Split (3 kernels) - reference:
tensor_model_parallel_all_reduce -> RMSNorm -> aiter per-1x128 quant.
2. Fused AR+RMSNorm + separate per-group quant (2 kernels):
tensor_model_parallel_fused_allreduce_rmsnorm -> aiter per-1x128 quant.
3. Fully fused AR+RMSNorm+per-group-quant (1 kernel):
tensor_model_parallel_fused_allreduce_rmsnorm_quant_per_group.
Default shape sets cover the Qwen3.5-397B-A17B-FP8 layout:
* hidden_size = 4096
* TP = 8 (launched with torchrun --nproc_per_node=8)
* Prefill batch sizes up to a few thousand tokens.
* Decode batch sizes 1-512 covering typical steady-state running_req values.
Usage:
torchrun --nproc_per_node=8 \
benchmark/kernels/all_reduce/benchmark_fused_ar_rms_quant_amd.py \
--dtype bf16 --group-size 128
"""
import argparse
import csv
import os
import statistics
from typing import Dict, List, Optional, Tuple
import torch
import torch.distributed as dist
import torch.nn.functional as F
from sglang.srt.distributed.communication_op import (
tensor_model_parallel_all_reduce,
tensor_model_parallel_fused_allreduce_rmsnorm,
tensor_model_parallel_fused_allreduce_rmsnorm_quant_per_group,
)
from sglang.srt.distributed.parallel_state import (
destroy_distributed_environment,
destroy_model_parallel,
graph_capture,
init_distributed_environment,
initialize_model_parallel,
set_custom_all_reduce,
)
Shape = Tuple[int, int]
FP8_DTYPE = torch.float8_e4m3fnuz
def parse_shapes(raw: str) -> List[Shape]:
shapes: List[Shape] = []
for item in [x.strip() for x in raw.split(",") if x.strip()]:
if "x" not in item:
raise ValueError(f"Invalid shape '{item}', expected MxN format.")
m_str, n_str = item.split("x", 1)
m, n = int(m_str), int(n_str)
if m <= 0 or n <= 0:
raise ValueError(f"Invalid shape '{item}', both dims must be positive.")
shapes.append((m, n))
if not shapes:
raise ValueError("Empty shape list is not allowed.")
return shapes
def dtype_from_name(name: str) -> torch.dtype:
mapping = {
"fp16": torch.float16,
"float16": torch.float16,
"bf16": torch.bfloat16,
"bfloat16": torch.bfloat16,
}
if name not in mapping:
raise ValueError(f"Unsupported dtype: {name}")
return mapping[name]
def _barrier(device: torch.device) -> None:
try:
dist.barrier(device_ids=[device.index])
except TypeError:
dist.barrier()
def _mean_across_ranks(val: float, device: torch.device) -> float:
t = torch.tensor([val], dtype=torch.float64, device=device)
dist.all_reduce(t, op=dist.ReduceOp.SUM)
t /= dist.get_world_size()
return float(t.item())
def _all_true_across_ranks(val: bool, device: torch.device) -> bool:
t = torch.tensor([1 if val else 0], dtype=torch.int32, device=device)
dist.all_reduce(t, op=dist.ReduceOp.MIN)
return bool(int(t.item()))
def _measure_us(
fn, warmup: int, iters: int, repeats: int, device: torch.device
) -> float:
for _ in range(max(1, warmup)):
fn()
torch.cuda.synchronize()
start = torch.cuda.Event(enable_timing=True)
end = torch.cuda.Event(enable_timing=True)
samples: List[float] = []
for _ in range(max(1, repeats)):
_barrier(device)
torch.cuda.synchronize()
start.record()
for _ in range(iters):
fn()
end.record()
end.synchronize()
samples.append(start.elapsed_time(end) * 1000.0 / iters)
samples.sort()
return float(statistics.median(samples))
def _make_inputs(
shape: Shape, dtype: torch.dtype, seed: int, rank: int, device: torch.device
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
m, n = shape
torch.manual_seed(seed + rank * 17)
# fp32 first then downcast so every rank has distinct values that still
# sum to a well-conditioned pre-norm tensor after all-reduce.
x = torch.randn((m, n), dtype=torch.float32, device=device).to(dtype)
residual = x.clone()
weight = torch.randn((n,), dtype=torch.float32, device=device).to(dtype)
return x, residual, weight
def _split_3_reference(
x: torch.Tensor,
residual: torch.Tensor,
weight: torch.Tensor,
eps: float,
group_size: int,
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
"""Reference: plain all_reduce -> RMSNorm -> aiter per-1x128 quant."""
import aiter
ar_out = tensor_model_parallel_all_reduce(x.clone())
residual_out = ar_out + residual
normed = F.rms_norm(residual_out, (residual_out.shape[-1],), weight, eps)
hip_quant = aiter.get_hip_quant(aiter.QuantType.per_1x128)
fp8_out, scale_out = hip_quant(normed, quant_dtype=aiter.dtypes.fp8)
return fp8_out, residual_out, scale_out
def _fused_ar_rms_then_quant(
x: torch.Tensor,
residual: torch.Tensor,
weight: torch.Tensor,
eps: float,
group_size: int,
) -> Optional[Tuple[torch.Tensor, torch.Tensor, torch.Tensor]]:
"""2-kernel: fused AR+RMSNorm (existing) + separate per-group quant."""
import aiter
result = tensor_model_parallel_fused_allreduce_rmsnorm(
x.clone(), residual.clone(), weight, eps
)
if result is None:
return None
normed, residual_out = result
hip_quant = aiter.get_hip_quant(aiter.QuantType.per_1x128)
fp8_out, scale_out = hip_quant(normed, quant_dtype=aiter.dtypes.fp8)
return fp8_out, residual_out, scale_out
def _fully_fused(
x: torch.Tensor,
residual: torch.Tensor,
weight: torch.Tensor,
eps: float,
group_size: int,
) -> Optional[Tuple[torch.Tensor, torch.Tensor, torch.Tensor]]:
"""1-kernel: fused AR+RMSNorm+per-group-quant (fp8+scale only)."""
return tensor_model_parallel_fused_allreduce_rmsnorm_quant_per_group(
x.clone(), residual.clone(), weight, eps, group_size
)
def _fully_fused_with_bf16(
x: torch.Tensor,
residual: torch.Tensor,
weight: torch.Tensor,
eps: float,
group_size: int,
) -> Optional[Tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor]]:
"""1-kernel: fused AR+RMSNorm+per-group-quant with bf16 side-output
(GDN keep_bf16=True path — replaces fused_ar_rms + separate per-group
quant with a single kernel that writes BOTH fp8+scale and bf16).
"""
return tensor_model_parallel_fused_allreduce_rmsnorm_quant_per_group(
x.clone(), residual.clone(), weight, eps, group_size, emit_bf16=True
)
def _check_quant_close(
fp8_a: torch.Tensor,
scale_a: torch.Tensor,
fp8_b: torch.Tensor,
scale_b: torch.Tensor,
group_size: int,
) -> Tuple[bool, str]:
"""Compare two (fp8, scale) per-group quantized outputs by dequantizing."""
dq_a = fp8_a.float() * scale_a.repeat_interleave(group_size, dim=-1)
dq_b = fp8_b.float() * scale_b.repeat_interleave(group_size, dim=-1)
max_diff = (dq_a - dq_b).abs().max().item()
denom = dq_a.abs().max().item() + 1e-6
rel_err = max_diff / denom
ok = rel_err < 0.15
return ok, f"max_diff={max_diff:.4f},rel={rel_err:.4f}"
def bench_shape(
x: torch.Tensor,
residual: torch.Tensor,
weight: torch.Tensor,
eps: float,
group_size: int,
warmup: int,
iters: int,
repeats: int,
mode: str,
) -> Dict[str, object]:
device = x.device
# --- Split 3-kernel baseline ---
split_fn = lambda: _split_3_reference(x, residual, weight, eps, group_size)
if mode == "graph":
with graph_capture() as gc:
g = torch.cuda.CUDAGraph()
with torch.cuda.graph(g, stream=gc.stream):
_split_3_reference(x, residual, weight, eps, group_size)
split_fn = g.replay
split_us = _measure_us(split_fn, warmup, iters, repeats, device)
# --- Fused AR+RMSNorm + separate quant (2 kernels) ---
probe2 = _fused_ar_rms_then_quant(x, residual, weight, eps, group_size)
fused2_available = probe2 is not None
fused2_us: Optional[float] = None
if fused2_available:
fused2_fn = lambda: _fused_ar_rms_then_quant(
x, residual, weight, eps, group_size
)
if mode == "graph":
with graph_capture() as gc:
g2 = torch.cuda.CUDAGraph()
with torch.cuda.graph(g2, stream=gc.stream):
_fused_ar_rms_then_quant(x, residual, weight, eps, group_size)
fused2_fn = g2.replay
fused2_us = _measure_us(fused2_fn, warmup, iters, repeats, device)
# --- Fully fused, fp8-only (1 kernel) — std-attention path ---
probe1 = _fully_fused(x, residual, weight, eps, group_size)
fused1_available = probe1 is not None
fused1_us: Optional[float] = None
if fused1_available:
fused1_fn = lambda: _fully_fused(x, residual, weight, eps, group_size)
if mode == "graph":
with graph_capture() as gc:
g1 = torch.cuda.CUDAGraph()
with torch.cuda.graph(g1, stream=gc.stream):
_fully_fused(x, residual, weight, eps, group_size)
fused1_fn = g1.replay
fused1_us = _measure_us(fused1_fn, warmup, iters, repeats, device)
# --- Fully fused, fp8+bf16 (1 kernel) — GDN keep_bf16=True path ---
probe1b = _fully_fused_with_bf16(x, residual, weight, eps, group_size)
# The bf16 side-output is only emitted when the call actually returned
# a 4-tuple; a 3-tuple means the aiter build doesn't support it.
fused1bf16_available = (
probe1b is not None and isinstance(probe1b, tuple) and len(probe1b) == 4
)
fused1bf16_us: Optional[float] = None
if fused1bf16_available:
fused1bf16_fn = lambda: _fully_fused_with_bf16(
x, residual, weight, eps, group_size
)
if mode == "graph":
with graph_capture() as gc:
g1b = torch.cuda.CUDAGraph()
with torch.cuda.graph(g1b, stream=gc.stream):
_fully_fused_with_bf16(x, residual, weight, eps, group_size)
fused1bf16_fn = g1b.replay
fused1bf16_us = _measure_us(fused1bf16_fn, warmup, iters, repeats, device)
# --- Correctness ---
# (a) fused1 fp8+scale vs fused2 fp8+scale (both emit fp8 pair)
# (b) fused1_bf16 bf16 side-output vs fused2 bf16 (both describe the
# same normed value; fused2 writes bf16 explicitly, fused1_bf16
# writes bf16 AND fp8; comparing bf16 against bf16 is the tightest
# check of the bf16 hook).
correctness = "N/A"
if fused1_available and fused2_available:
res1 = _fully_fused(x, residual, weight, eps, group_size)
res2 = _fused_ar_rms_then_quant(x, residual, weight, eps, group_size)
ok, detail = _check_quant_close(res2[0], res2[2], res1[0], res1[2], group_size)
correctness = "PASS" if ok else f"FAIL({detail})"
correctness_bf16 = "N/A"
if fused1bf16_available and fused2_available:
res1b = _fully_fused_with_bf16(x, residual, weight, eps, group_size)
res2 = _fused_ar_rms_then_quant(x, residual, weight, eps, group_size)
# res1b = (fp8, res_out, scale, bf16); res2 = (fp8, res_out, scale)
# Cross-check: dequant(res1b.fp8) ≈ dequant(res2.fp8) and
# res1b.bf16 ≈ dequant(res1b.fp8) within ~one FP8 step.
ok_fp8, detail_fp8 = _check_quant_close(
res2[0], res2[2], res1b[0], res1b[2], group_size
)
bf16_vs_fp8 = (
(
res1b[3].float()
- (res1b[0].float() * res1b[2].repeat_interleave(group_size, dim=-1))
)
.abs()
.max()
.item()
)
if not ok_fp8:
correctness_bf16 = f"FAIL_fp8({detail_fp8})"
elif bf16_vs_fp8 > 1.0:
correctness_bf16 = f"FAIL_bf16(diff={bf16_vs_fp8:.4f})"
else:
correctness_bf16 = f"PASS(bf16_diff={bf16_vs_fp8:.3f})"
return {
"split_us": split_us,
"fused2_available": fused2_available,
"fused2_us": fused2_us,
"fused1_available": fused1_available,
"fused1_us": fused1_us,
"fused1bf16_available": fused1bf16_available,
"fused1bf16_us": fused1bf16_us,
"correctness": correctness,
"correctness_bf16": correctness_bf16,
}
# Qwen3.5-397B-A17B-FP8 has hidden_size=4096 (both GDN and standard attention
# layers go through input_layernorm at full hidden dim before the TP projections
# are applied, so the fused op sees [M, 4096] inputs on every rank).
_DEFAULT_PREFILL_SHAPES = (
"64x4096,128x4096,256x4096,512x4096,1024x4096,2048x4096,4096x4096,8192x4096"
)
_DEFAULT_DECODE_SHAPES = (
"1x4096,2x4096,4x4096,8x4096,16x4096,32x4096,64x4096,128x4096,256x4096,512x4096"
)
def main() -> None:
parser = argparse.ArgumentParser(
description=(
"Benchmark fused AR+RMSNorm+per-group-quant for Qwen3.5-FP8 shapes."
)
)
parser.add_argument(
"--dtype",
type=str,
default="bf16",
choices=["fp16", "bf16", "float16", "bfloat16"],
)
parser.add_argument("--eps", type=float, default=1e-6)
parser.add_argument("--seed", type=int, default=1234)
parser.add_argument("--group-size", type=int, default=128)
parser.add_argument("--prefill-shapes", type=str, default=_DEFAULT_PREFILL_SHAPES)
parser.add_argument("--decode-shapes", type=str, default=_DEFAULT_DECODE_SHAPES)
parser.add_argument("--warmup", type=int, default=10)
parser.add_argument("--iters", type=int, default=30)
parser.add_argument("--repeats", type=int, default=5)
parser.add_argument(
"--mode",
type=str,
default="both",
choices=["eager", "graph", "both"],
)
parser.add_argument("--csv-out", type=str, default=None)
args = parser.parse_args()
dtype = dtype_from_name(args.dtype)
rank = int(os.environ.get("RANK", "0"))
world_size = int(os.environ.get("WORLD_SIZE", "1"))
local_rank = int(os.environ.get("LOCAL_RANK", str(rank)))
torch.cuda.set_device(local_rank % torch.cuda.device_count())
device = torch.device(f"cuda:{local_rank % torch.cuda.device_count()}")
set_custom_all_reduce(True)
init_distributed_environment(
world_size=world_size,
rank=rank,
local_rank=local_rank,
distributed_init_method="env://",
backend="nccl",
)
initialize_model_parallel(tensor_model_parallel_size=world_size)
if rank == 0:
print(
f"Config: world_size={world_size}, dtype={dtype}, "
f"group_size={args.group_size}"
)
print(
f" 1-stage boundary: total_bytes <= 128KB "
f"(M <= {128 * 1024 // (4096 * 2)} for hidden=4096 bf16)"
)
print(
f" 2-stage boundary: total_bytes <= 512KB "
f"(M <= {512 * 1024 // (4096 * 2)} for hidden=4096 bf16)"
)
print(
" fallback: fused_ar_rms + per_group_quant (2 kernels) "
"when single-kernel path is unavailable"
)
run_modes = ("eager", "graph") if args.mode == "both" else (args.mode,)
csv_rows: List[Dict[str, object]] = []
for mode in run_modes:
shapes = parse_shapes(
args.prefill_shapes if mode == "eager" else args.decode_shapes
)
if rank == 0:
phase = "prefill(eager)" if mode == "eager" else "decode(graph)"
print(f"\n{'=' * 145}")
print(f"Mode: {phase}")
print(
"| Shape | Bytes/rank | Split(3k) us | Fused2(2k) us | "
"Fused1(1k) us | Fused1+bf16(1k) us | Speedup(2k) | "
"Speedup(1k) | Speedup(1k+bf16) | Corr fp8 | Corr bf16 |"
)
print(
"|:------|----------:|-----------:|------------:|-----------:|"
"-----------:|-----------:|-----------:|-----------:|"
":---------|:----------|"
)
for shape in shapes:
x, residual, weight = _make_inputs(shape, dtype, args.seed, rank, device)
m = bench_shape(
x,
residual,
weight,
args.eps,
args.group_size,
args.warmup,
args.iters,
args.repeats,
mode,
)
split_us = _mean_across_ranks(m["split_us"], device)
fused2_avail = _all_true_across_ranks(m["fused2_available"], device)
fused1_avail = _all_true_across_ranks(m["fused1_available"], device)
fused1bf16_avail = _all_true_across_ranks(m["fused1bf16_available"], device)
fused2_us = (
_mean_across_ranks(m["fused2_us"], device)
if m["fused2_us"] is not None
else None
)
fused1_us = (
_mean_across_ranks(m["fused1_us"], device)
if m["fused1_us"] is not None
else None
)
fused1bf16_us = (
_mean_across_ranks(m["fused1bf16_us"], device)
if m["fused1bf16_us"] is not None
else None
)
if rank == 0:
M, N = shape
nbytes = M * N * 2
f2_str = f"{fused2_us:.1f}" if fused2_us else "N/A"
f1_str = f"{fused1_us:.1f}" if fused1_us else "N/A"
f1b_str = f"{fused1bf16_us:.1f}" if fused1bf16_us else "N/A"
s2 = (
f"{split_us / fused2_us:.2f}x"
if fused2_us and fused2_us > 0
else "N/A"
)
s1 = (
f"{split_us / fused1_us:.2f}x"
if fused1_us and fused1_us > 0
else "N/A"
)
s1b = (
f"{fused2_us / fused1bf16_us:.2f}x"
if fused1bf16_us and fused2_us and fused1bf16_us > 0
else "N/A"
)
print(
f"| {M}x{N} | {nbytes} | {split_us:.1f} | {f2_str} | "
f"{f1_str} | {f1b_str} | {s2} | {s1} | {s1b} | "
f"{m['correctness']} | {m['correctness_bf16']} |"
)
csv_rows.append(
{
"mode": mode,
"shape": f"{M}x{N}",
"m": M,
"n": N,
"bytes_per_rank": nbytes,
"split_us": split_us,
"fused2_us": fused2_us if fused2_us is not None else "",
"fused1_us": fused1_us if fused1_us is not None else "",
"fused1bf16_us": (
fused1bf16_us if fused1bf16_us is not None else ""
),
"fused1_available": fused1_avail,
"fused2_available": fused2_avail,
"fused1bf16_available": fused1bf16_avail,
"correctness": m["correctness"],
"correctness_bf16": m["correctness_bf16"],
}
)
if rank == 0 and args.csv_out and csv_rows:
os.makedirs(os.path.dirname(args.csv_out) or ".", exist_ok=True)
with open(args.csv_out, "w", newline="") as f:
w = csv.DictWriter(f, fieldnames=list(csv_rows[0].keys()))
w.writeheader()
w.writerows(csv_rows)
print(f"\nSaved CSV: {args.csv_out}")
_barrier(device)
destroy_model_parallel()
destroy_distributed_environment()
if __name__ == "__main__":
main()