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enginex-mlu370-vllm/vllm-v0.6.2/vllm/compilation/fusion.py
2026-02-04 17:22:39 +08:00

292 lines
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Python

import operator
from typing import Iterable, List, Optional
import torch
from torch._higher_order_ops.auto_functionalize import auto_functionalized
from torch._inductor.pattern_matcher import (Match, PatternMatcherPass,
fwd_only, register_replacement)
from vllm.compilation.config import CompilationConfig
from vllm.compilation.inductor_pass import InductorPass
from vllm.logger import init_logger
logger = init_logger(__name__)
def rms_pattern_static(result: torch.Tensor, result_rms: torch.Tensor,
input: torch.Tensor, weight: torch.Tensor,
scale: torch.Tensor):
at1 = auto_functionalized(torch.ops._C.rms_norm.default,
result=result_rms,
input=input,
weight=weight,
epsilon=1e-5)
at2 = auto_functionalized(torch.ops._C.static_scaled_fp8_quant.default,
result=result,
input=at1[1],
scale=scale)
# result
return at2[1]
def rms_replacement_static(result: torch.Tensor, result_rms: torch.Tensor,
input: torch.Tensor, weight: torch.Tensor,
scale: torch.Tensor):
at = auto_functionalized(torch.ops._C.rms_norm_static_fp8_quant.default,
result=result,
input=input,
weight=weight,
scale=scale,
epsilon=1e-5)
# result
return at[1]
def rms_pattern_residual_static(result: torch.Tensor, input: torch.Tensor,
residual: torch.Tensor, weight: torch.Tensor,
scale: torch.Tensor):
at = auto_functionalized(torch.ops._C.fused_add_rms_norm.default,
input=input,
residual=residual,
weight=weight,
epsilon=1e-5)
at1 = auto_functionalized(torch.ops._C.static_scaled_fp8_quant.default,
result=result,
input=at[1],
scale=scale)
# result, residual
return at1[1], at[2]
def rms_replacement_residual_static(result: torch.Tensor, input: torch.Tensor,
residual: torch.Tensor,
weight: torch.Tensor, scale: torch.Tensor):
at = auto_functionalized(
torch.ops._C.fused_add_rms_norm_static_fp8_quant.default,
result=result,
input=input,
residual=residual,
weight=weight,
scale=scale,
epsilon=1e-5)
# result, residual
return at[1], at[2]
def empty_bf16(*args, **kwargs):
return torch.empty(*args, **kwargs, dtype=torch.bfloat16, device="cuda")
def empty_fp8(*args, **kwargs):
fp8 = torch.float8_e4m3fn
return torch.empty(*args, **kwargs, dtype=fp8, device="cuda")
def empty_fp32(*args, **kwargs):
return torch.empty(*args, **kwargs, dtype=torch.float32, device="cuda")
# Utilities for post-processing multi-output matches
def is_func(node: torch.fx.Node, target) -> bool:
return node.op == "call_function" and node.target == target
# Returns the first auto_functionalized node with the given op (if it exists)
def find_auto_fn_maybe(nodes: Iterable[torch.fx.Node],
op) -> Optional[torch.fx.Node]:
for node in nodes:
if is_func(node, auto_functionalized) and node.args[0] == op: # noqa
return node
return None
# Returns the first auto_functionalized node with the given op
def find_auto_fn(nodes: Iterable[torch.fx.Node], op) -> torch.fx.Node:
node = find_auto_fn_maybe(nodes, op)
assert node is not None, f"Could not find {op} in nodes {nodes}"
return node
# Returns the getitem node that extracts the idx-th element from node
# (if it exists)
def find_getitem_maybe(node: torch.fx.Node,
idx: int) -> Optional[torch.fx.Node]:
for user in node.users:
if is_func(user, operator.getitem) and user.args[1] == idx:
return user
return None
# Returns the getitem node that extracts the idx-th element from node
def find_getitem(node: torch.fx.Node, idx: int) -> torch.fx.Node:
ret = find_getitem_maybe(node, idx)
assert ret is not None, f"Could not find getitem {idx} in node {node}"
return ret
class FusionPass(InductorPass):
"""
This pass fuses a pre-defined set of custom ops into fused ops.
It uses the torch pattern matcher to find the patterns and replace them.
It also manually processes multi-output matches, as those are broken in
the torch pattern matcher.
Because patterns can only be registered once, the pass is a singleton.
This will be addressed in a future version of PyTorch:
https://github.com/pytorch/pytorch/pull/139321#issuecomment-2452354980
"""
_instance: 'Optional[FusionPass]' = None
@classmethod
def instance(cls, config: CompilationConfig):
"""
Get the singleton instance of the FusionPass.
If the instance exists, the config is updated but
initialization is not repeated.
"""
if cls._instance is None:
cls._instance = FusionPass(config)
else:
cls._instance.config = config
return cls._instance
def __init__(self, config: CompilationConfig):
assert self.__class__._instance is None, \
"FusionPass singleton instance already exists"
super().__init__(config)
self.matches: List[Match] = []
self.patterns: PatternMatcherPass = PatternMatcherPass(
pass_name="fusion_pass")
# Fuse rms_norm + static_scaled_fp8_quant into
# rms_norm_static_fp8_quant
inputs = [
empty_fp8(5, 4),
empty_bf16(5, 4),
empty_bf16(5, 4),
empty_bf16(1, 5),
empty_fp32(1, 1)
]
register_replacement(rms_pattern_static, rms_replacement_static,
inputs, fwd_only, self.patterns)
# Fuse fused_add_rms_norm + static_scaled_fp8_quant into
# fused_add_rms_norm_static_fp8_quant
# Because pattern has 2 outputs, we need to manually process the match
# (see process_matches)
inputs = [
empty_fp8(5, 4),
empty_bf16(5, 4),
empty_bf16(5, 4),
empty_bf16(1, 5),
empty_fp32(1, 1)
]
register_replacement(rms_pattern_residual_static,
rms_replacement_residual_static,
inputs,
fwd_only,
self.patterns,
extra_check=lambda m: self.record_match(m))
def record_match(self, match: Match) -> bool:
# Hijack the extra_check to record the match and
# save it for post-processing.
self.matches.append(match)
# Return False to prevent automatic replacement.
return False
def process_matches(self, graph: torch.fx.Graph):
"""
Manually process multi-output matches and replace them with fused nodes.
This is necessary because the automatic replacement for multi-output
matches is broken: https://github.com/pytorch/pytorch/issues/137280
"""
for match in self.matches:
# To avoid use-before-definition errors, insert replacement nodes
# after the last node in the match.
# match.nodes is not guaranteed to be sorted.
# Find the last node in the match.
for last_node_in_match in reversed(graph.nodes):
if last_node_in_match in match.nodes:
break
else:
raise ValueError("No nodes in graph")
# Insert a new auto_functionalized node for the fused operation,
# as well as getitem nodes to extract the result and residual.
# The auto_functionalized node returns a tuple of
# (None, result, residual) - None is the function return value.
# The resulting graph looks like this:
# at = auto_functionalized(torch.ops._C.fused_add_rms_norm_static_fp8_quant.default, ...) # noqa
# result_node_new = at[1]
# residual_node_new = at[2]
with graph.inserting_after(last_node_in_match):
kwargs = match.kwargs
kwargs["epsilon"] = 1e-5 # Currently hard-coded in RMSNorm
fused_node = graph.call_function(
auto_functionalized,
(torch.ops._C.fused_add_rms_norm_static_fp8_quant.default,
),
kwargs=kwargs)
graph.inserting_after(fused_node)
result_node_new = graph.call_function(operator.getitem,
(fused_node, 1))
residual_node_new = graph.call_function(
operator.getitem, (fused_node, 2))
# Last part of replacement is rebinding the users of nodes in the
# match to use the new nodes.
# Find the nodes in the match that we need to rebind
rms_node = find_auto_fn(match.nodes,
torch.ops._C.fused_add_rms_norm.default)
quant_node = find_auto_fn(
match.nodes, torch.ops._C.static_scaled_fp8_quant.default)
assert len(rms_node.users) == 2
assert len(quant_node.users) == 1
# meta["val"] is used by de-functionalization and has to contain the
# value of the node (tuple of tensors) that would be returned by the
# functionalized node during tracing.
rms_tup = rms_node.meta["val"]
quant_tup = quant_node.meta["val"]
# The result of fused_node must be a tuple with the first element
# None (the function return value) and the remaining elements
# representing the mutated inputs.
fused_tup = (None, quant_tup[1], rms_tup[1], rms_tup[2])
fused_node.meta["val"] = fused_tup
# Find the getitem nodes and replace their uses with the new nodes.
# The old nodes will be removed by DCE at the end of the pass.
find_getitem(rms_node, 2).replace_all_uses_with(residual_node_new)
find_getitem(quant_node, 1).replace_all_uses_with(result_node_new)
# Finally, remove matched nodes
graph.eliminate_dead_code()
assert all(node not in graph.nodes for match in self.matches
for node in match.nodes)
def __call__(self, graph: torch.fx.Graph):
self.dump_graph(graph, "before_fusion")
count = self.patterns.apply(graph)
logger.debug("Replaced %s patterns", count)
self.dump_graph(graph, "after_pattern_match")
# Manually process multi-output matches (and run DCE)
self.process_matches(graph)
logger.debug("Post-processed %s matches", len(self.matches))
self.dump_graph(graph, "after_fusion")
self.matches.clear()