[diffusion] improve: norm fusion for z-image (#18762)

Signed-off-by: Chi McIsaac <chixie.mcisaac@gmail.com>
Co-authored-by: yihanc <yingluosanqian@gmail.com>
Co-authored-by: Mick <mickjagger19@icloud.com>
This commit is contained in:
Chi McIsaac
2026-04-04 14:01:01 +08:00
committed by GitHub
co-authored by yihanc Mick
parent ef13031243
commit 005e582d06
4 changed files with 602 additions and 8 deletions
@@ -0,0 +1,379 @@
from typing import Optional, Tuple
import cuda.bindings.driver as cuda
import cutlass
import cutlass.cute as cute
import torch
from sglang.jit_kernel.diffusion.cutedsl.common.norm_fusion import (
apply_norm_cta,
broadcast_tensor_for_bsfd,
tensor_slice_for_bsfd,
)
from sglang.jit_kernel.diffusion.cutedsl.utils import TORCH_TO_CUTE_DTYPE, WARP_SIZE
_COMPILE_CACHE = {}
def to_cute_arg(
t,
*,
assume_aligned: Optional[int] = 32,
use_32bit_stride: bool = False,
enable_tvm_ffi: bool = True,
):
"""
Convert a Python value into a CuTeDSL value.
"""
if isinstance(t, torch.Tensor):
return cute.runtime.from_dlpack(
t,
assumed_align=assume_aligned,
use_32bit_stride=use_32bit_stride,
enable_tvm_ffi=enable_tvm_ffi,
)
if isinstance(t, int):
return cutlass.Int32(t)
if isinstance(t, float):
return cutlass.Float32(t)
return t
def to_fake_cute_args(t: torch.Tensor):
if isinstance(t, torch.Tensor):
# Only keep the last dim as compile-time value to maximum compiled kernel reuse
# e.g. (1,2,1536):(3027,1536,1) -> (?,?,1536):(?,?,1)
D = t.shape[-1]
dtype = TORCH_TO_CUTE_DTYPE[t.dtype]
shape = (*(cute.sym_int() for _ in range(t.ndim - 1)), D)
stride = (*(cute.sym_int(divisibility=D) for _ in range(t.ndim - 1)), 1)
fake_t = cute.runtime.make_fake_tensor(
dtype, shape, stride, memspace=cute.AddressSpace.gmem, assumed_align=32
)
return fake_t
return to_cute_arg(t)
class NormTanhMulAddNormScale:
@classmethod
def make_hash_key(cls, *inputs):
"""
Compile-time values:
- D: hidden dimension (size of the last dimension)
- norm_type: layer norm or RMS norm
- tensor dtype
- tensor rank (i.e., tensor.ndim)
Runtime values:
- all other inputs
This hash key defines the compile-time specialization boundary for
NormTanhMulAddNormScale kernels.
"""
def _sig(val):
if isinstance(val, torch.Tensor):
return (val.dtype, val.ndim, val.shape[-1])
return val
return tuple(_sig(val) for val in inputs)
def __init__(self, D: int, norm_type: str, is_norm2: bool):
self.D = D
self.norm_type = norm_type # "layer" or "rms"
self.is_norm2 = is_norm2 # single norm or double norm
self.num_warps = self.D // 256 # num of warps per cta
self.num_threads = self.num_warps * WARP_SIZE # num of threads per cta
@cute.jit
def __call__(
self,
mY,
mY2,
mX,
mWeight,
mBias,
mScale,
mShift,
mWeight2,
mBias2,
mScale2,
eps: cutlass.Float32 = cutlass.Float32(1e-5),
stream: cuda.CUstream = cuda.CUstream(cuda.CUstream_flags.CU_STREAM_DEFAULT),
):
# Tensor shapes
B, S, _ = mX.shape # (batch, seq_len, hidden_dim)
# Vectorized copy configuration
num_vectorized = 8 # maximum num of elem per copy
atom_copy = cute.make_copy_atom(
cute.nvgpu.CopyUniversalOp(),
mX.element_type,
num_bits_per_copy=128,
)
# Thread/value layouts for tiled copy
t_layout = cute.make_layout(self.num_threads) # thread layout within a CTA
v_layout = cute.make_layout(num_vectorized) # per-thread vector layout
tiled_copy = cute.make_tiled_copy_tv(atom_copy, t_layout, v_layout)
self.kernel(
mY,
mY2,
mX,
mWeight,
mBias,
mScale,
mShift,
mWeight2,
mBias2,
mScale2,
tiled_copy,
eps,
).launch(
grid=[B * S, 1, 1],
block=[self.num_threads, 1, 1],
stream=stream,
)
@cute.kernel
def kernel(
self,
mY,
mY2,
mX,
mWeight,
mBias,
mScale,
mShift,
mWeight2,
mBias2,
mScale2,
tiled_copy: cute.TiledCopy,
eps: cutlass.Float32,
):
_, S, _ = mX.shape
tidx, _, _ = cute.arch.thread_idx() # thread index
bid, _, _ = cute.arch.block_idx() # cta index
bidx = cutlass.Int32(bid // S) # batch index
bidy = cutlass.Int32(bid % S) # seq_len index
thr_copy = tiled_copy.get_slice(tidx)
@cute.jit
def slice_if(mV):
if cutlass.const_expr(isinstance(mV, cute.Tensor)):
return tensor_slice_for_bsfd(mV, thr_copy, bidx, bidy, S, self.D)
return mV, mV
@cute.jit
def copy_if(src, dst):
if cutlass.const_expr(
isinstance(src, cute.Tensor) and isinstance(src, cute.Tensor)
):
cute.autovec_copy(src, dst) # LDG.128
@cute.jit
def norm(x, weight, bias):
return apply_norm_cta(
self.norm_type, self.num_warps, tidx, x, weight, bias, self.D, eps
)
# Slice: retrieve the per-thread data slices for both global memory (gmem)
tXgX, tXrX = slice_if(mX) # x
tWgW, tWrW = slice_if(mWeight) # weight
tBgB, tBrB = slice_if(mBias) # bias
tSCgSC, tSCrSC = slice_if(mScale) # scale
tSHgSH, tSHrSH = slice_if(mShift) # shift
tYgY, tYrY = slice_if(mY) # y
if cutlass.const_expr(self.is_norm2):
tYgY2, tYrY2 = slice_if(mY2) # y2
tWgW2, tWrW2 = slice_if(mWeight2) # weight2
tBgB2, tBrB2 = slice_if(mBias2) # bias2
tSCgSC2, tSCrSC2 = slice_if(mScale2) # scale2
# Load: load tensor from global memory to registers
copy_if(tXgX, tXrX) # gmem -> rmem
copy_if(tWgW, tWrW) # gmem -> rmem
copy_if(tBgB, tBrB) # gmem -> rmem
tNrN = norm(tXrX, tWrW, tBrB)
# Compute: value = value * tanh(<scale>) + <shift>
copy_if(tSCgSC, tSCrSC) # gmem -> rmem
copy_if(tSHgSH, tSHrSH) # gmem -> rmem
value = tNrN.load() * cute.tanh(tSCrSC.load()) + tSHrSH.load()
# Store: y
tYrY.store(value.to(tYrY.element_type))
copy_if(tYrY, tYgY) # rmem -> gmem
if cutlass.const_expr(self.is_norm2):
copy_if(tWgW2, tWrW2) # gmem -> rmem
copy_if(tBgB2, tBrB2) # gmem -> rmem
tNrN2 = norm(tYrY, tWrW2, tBrB2)
# Compute: value2 = value2 * (1 + <scale2>)
copy_if(tSCgSC2, tSCrSC2) # gmem -> rmem
value2 = tNrN2.load() * (1 + tSCrSC2.load())
# Store: y2
tYrY2.store(value2.to(tYrY2.element_type))
copy_if(tYrY2, tYgY2) # rmem -> gmem
def validate_3d(t: torch.Tensor, B: int, S: int, D: int):
if t.dtype not in (torch.float16, torch.bfloat16, torch.float32):
raise ValueError(f"Validate failed: unsupported dtype: {t.dtype}")
if (
t.ndim != 3
or (t.shape[0] not in (1, B))
or (t.shape[1] not in (1, S) or t.shape[2] != D)
):
raise ValueError(f"Validate failed: unsupported 3d-tensor: {t.shape}.")
if t.stride()[-1] != 1:
raise ValueError(f"Validate failed: not contiguous on dim D.")
def validate_weight_bias(t: Optional[torch.Tensor], D: int):
if t is None:
return
if t.dtype not in (torch.float16, torch.bfloat16, torch.float32):
raise ValueError(f"Validate failed: unsupported dtype: {t.dtype}")
if t.shape != (D,):
raise ValueError(f"Validate failed: unsupported tensor shape: {t.shape}.")
if t.stride()[-1] != 1:
raise ValueError(f"Validate failed: not contiguous on dim D.")
@torch.library.custom_op("sglang::fused_norm_tanh_mul_add", mutates_args=())
def fused_norm_tanh_mul_add(
x: torch.Tensor,
weight: Optional[torch.Tensor],
bias: Optional[torch.Tensor],
scale: torch.Tensor,
shift: torch.Tensor,
norm_type: str,
eps: float = 1e-5,
) -> torch.Tensor:
"""
Fuse: norm(x) * tanh(scale) + shift
where norm is either layernorm or rmsnorm.
Expects:
- x: [B, S, D]
- weight/bias: None, [D]
- scale/shift: [1/B, 1/S, D]
- norm_type: str, "layer" or "rms"
- eps: Optional[float], default: 1e-5
D must be a multiple of 256 and <= 8192 to enable LDG.128 vectorized loads per
thread and avoid predicated loads (e.g., bounds checks such as `index < D`).
"""
stream = cuda.CUstream(torch.cuda.current_stream().cuda_stream)
# Tensor Validation
BSD = x.shape
validate_3d(x, *BSD)
validate_weight_bias(weight, BSD[2])
validate_weight_bias(bias, BSD[2])
validate_3d(scale, *BSD)
validate_3d(shift, *BSD)
if norm_type == "layer" or norm_type == "rms":
D = x.shape[-1]
if D % 256 != 0 or D > 8192:
raise ValueError(
f"D={D} not supported, must be multiple of 256 and <= 8192"
)
y = torch.empty_like(x) # create output tensor
scale = broadcast_tensor_for_bsfd(scale, *x.shape) # handle various shapes
shift = broadcast_tensor_for_bsfd(shift, *x.shape) # handle various shapes
# y2, weight2, bias2, scale2 is None
torch_tensors = [y, None, x, weight, bias, scale, shift, None, None, None]
cute_tensor_args = [to_cute_arg(t) for t in torch_tensors]
# Compile cache
hash_key = NormTanhMulAddNormScale.make_hash_key(norm_type, *torch_tensors)
compiled_fn = _COMPILE_CACHE.get(hash_key)
if compiled_fn is None:
kernel = NormTanhMulAddNormScale(D, norm_type, is_norm2=False)
fake_sig_args = [to_fake_cute_args(t) for t in torch_tensors]
compiled_fn = cute.compile(
kernel, *fake_sig_args, options="--enable-tvm-ffi"
)
_COMPILE_CACHE[hash_key] = compiled_fn
# Execute
compiled_fn(*cute_tensor_args, eps, stream)
return y
else:
raise ValueError(f'norm_type must be one of "layer" and "rms"')
@fused_norm_tanh_mul_add.register_fake
def _fused_norm_tanh_mul_add_fake(x, weight, bias, scale, shift, norm_type, eps=1e-5):
return x.new_empty(x.shape)
@torch.library.custom_op("sglang::fused_norm_tanh_mul_add_norm_scale", mutates_args=())
def fused_norm_tanh_mul_add_norm_scale(
x: torch.Tensor,
weight: Optional[torch.Tensor],
bias: Optional[torch.Tensor],
scale: torch.Tensor,
shift: torch.Tensor,
weight2: Optional[torch.Tensor],
bias2: Optional[torch.Tensor],
scale2: torch.Tensor,
norm_type: str,
eps: float = 1e-5,
) -> Tuple[torch.Tensor, torch.Tensor]:
"""
Fuse:
y = norm(x) * tanh(scale) + shift
y2 = norm(y) * (1 + scale2)
where norm is either layernorm or rmsnorm.
Expects:
- x: [B, S, D]
- weight/bia/weight2/bias2: None, [D]
- scale/shift/scale2: [1/B, 1/S, D]
- norm_type: str, "layer" or "rms"
- eps: Optional[float], default: 1e-5
D must be a multiple of 256 and <= 8192 to enable LDG.128 vectorized loads per
thread and avoid predicated loads (e.g., bounds checks such as `index < D`).
"""
stream = cuda.CUstream(torch.cuda.current_stream().cuda_stream)
# Tensor Validation
BSD = x.shape
validate_3d(x, *BSD)
validate_weight_bias(weight, BSD[2])
validate_weight_bias(bias, BSD[2])
validate_3d(scale, *BSD)
validate_3d(shift, *BSD)
validate_weight_bias(weight2, BSD[2])
validate_weight_bias(bias2, BSD[2])
validate_3d(scale2, *BSD)
if norm_type == "layer" or norm_type == "rms":
D = x.shape[-1]
if D % 256 != 0 or D > 8192:
raise ValueError(
f"D={D} not supported, must be multiple of 256 and <= 8192"
)
y = torch.empty_like(x) # create output tensor
y2 = torch.empty_like(x) # create output tensor
scale = broadcast_tensor_for_bsfd(scale, *x.shape) # handle various shapes
shift = broadcast_tensor_for_bsfd(shift, *x.shape) # handle various shapes
scale2 = broadcast_tensor_for_bsfd(scale2, *x.shape) # handle various shapes
torch_tensors = [y, y2, x, weight, bias, scale, shift, weight2, bias2, scale2]
cute_tensor_args = [to_cute_arg(t) for t in torch_tensors]
# Compile cache
hash_key = NormTanhMulAddNormScale.make_hash_key(norm_type, *torch_tensors)
compiled_fn = _COMPILE_CACHE.get(hash_key)
if compiled_fn is None:
kernel = NormTanhMulAddNormScale(D, norm_type, is_norm2=True)
fake_sig_args = [to_fake_cute_args(t) for t in torch_tensors]
compiled_fn = cute.compile(
kernel, *fake_sig_args, options="--enable-tvm-ffi"
)
_COMPILE_CACHE[hash_key] = compiled_fn
# Execute
compiled_fn(*cute_tensor_args, eps, stream)
return y, y2
else:
raise ValueError(f'norm_type must be one of "layer" and "rms"')
@fused_norm_tanh_mul_add_norm_scale.register_fake
def _fused_norm_tanh_mul_add_norm_scale_fake(
x, weight, bias, scale, shift, weight2, bias2, scale2, norm_type, eps=1e-5
):
return x.new_empty(x.shape), x.new_empty(x.shape)