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sglang/python/sglang/multimodal_gen/runtime/ipc_array.py
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Python

# SPDX-License-Identifier: Apache-2.0
"""Helpers for transferring large arrays between local scheduler processes."""
from __future__ import annotations
import os
import tempfile
from dataclasses import dataclass
from pathlib import Path
from typing import Any
import numpy as np
import torch
from sglang.multimodal_gen.runtime.utils.logging_utils import init_logger
logger = init_logger(__name__)
_MIN_FILE_REF_BYTES = 32 << 20
@dataclass
class NumpyArrayFileRef:
path: str
def materialize(self) -> np.ndarray:
try:
return np.load(self.path, allow_pickle=False)
finally:
try:
os.unlink(self.path)
except FileNotFoundError:
pass
@dataclass
class TorchTensorFileRef:
"""A tensor spilled as raw bytes; dtype and shape are restored on the far side."""
ref: NumpyArrayFileRef
dtype: str
shape: tuple[int, ...]
def materialize(self) -> torch.Tensor:
flat = torch.from_numpy(self.ref.materialize())
return flat.view(getattr(torch, self.dtype)).reshape(self.shape)
def is_local_endpoint(endpoint: str) -> bool:
return endpoint.startswith(
("tcp://127.0.0.1:", "tcp://localhost:", "ipc://", "inproc://")
)
def spill_large_arrays_to_file_refs(value: Any) -> Any:
directory = _array_ipc_dir()
if directory is None:
return value
return _spill_large_arrays_to_file_refs(value, directory)
def _spill_large_arrays_to_file_refs(value: Any, directory: str) -> Any:
# A payload that does not fit in shared memory is still deliverable inline,
# so a full /dev/shm slows the reply down instead of failing the request.
if isinstance(value, np.ndarray) and value.nbytes >= _MIN_FILE_REF_BYTES:
# only spill if the array size is above the threshold. if not, it's not worth it
try:
return _spill_array(value, directory)
except OSError:
logger.warning_once(
f"Spilling an array to {directory} failed; sending it inline."
)
return value
if _is_large_tensor(value):
try:
return _spill_tensor(value, directory)
except OSError:
logger.warning_once(
f"Spilling a tensor to {directory} failed; sending it inline."
)
return value
if isinstance(value, list):
return [_spill_large_arrays_to_file_refs(item, directory) for item in value]
if isinstance(value, tuple):
return tuple(
_spill_large_arrays_to_file_refs(item, directory) for item in value
)
return value
def materialize_file_refs(value: Any) -> Any:
if isinstance(value, (NumpyArrayFileRef, TorchTensorFileRef)):
return value.materialize()
if isinstance(value, list):
return [materialize_file_refs(item) for item in value]
if isinstance(value, tuple):
return tuple(materialize_file_refs(item) for item in value)
return value
def _spill_array(array: np.ndarray, directory: str) -> NumpyArrayFileRef:
if not array.flags.c_contiguous:
array = np.ascontiguousarray(array)
fd, path = tempfile.mkstemp(
prefix="sgldiffusion-array-",
suffix=".npy",
dir=directory,
)
try:
with os.fdopen(fd, "wb") as f:
np.save(f, array, allow_pickle=False)
except Exception:
try:
os.unlink(path)
except FileNotFoundError:
pass
raise
return NumpyArrayFileRef(path=path)
def _is_large_tensor(value: Any) -> bool:
return (
isinstance(value, torch.Tensor)
and value.numel() * value.element_size() >= _MIN_FILE_REF_BYTES
)
def _spill_tensor(tensor: torch.Tensor, directory: str) -> TorchTensorFileRef:
host = tensor.detach().to("cpu", copy=False).contiguous()
# Spill the raw bytes: numpy has no bfloat16, and the byte view needs no
# dtype table to stay exact.
array = host.reshape(-1).view(torch.uint8).numpy()
return TorchTensorFileRef(
ref=_spill_array(array, directory),
dtype=str(host.dtype).removeprefix("torch."),
shape=tuple(host.shape),
)
def _array_ipc_dir() -> str | None:
shm_path = Path("/dev/shm")
if shm_path.is_dir() and os.access(shm_path, os.W_OK):
return str(shm_path)
return None