[CAR] Let custom allreduce support VMM based allocation (#27593)
Co-authored-by: Lianmin Zheng <lianminzheng@gmail.com>
This commit is contained in:
Yinghai Lu
co-authored by
Lianmin Zheng
Lianmin Zheng
parent
12ebb35439
commit
fcca4611fa
@@ -12,6 +12,10 @@ from sglang.srt.distributed.device_communicators.custom_all_reduce_utils import
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can_use_custom_all_reduce_with_nvlink,
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is_weak_contiguous,
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)
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from sglang.srt.distributed.device_communicators.custom_all_reduce_vmm_utils import (
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VmmGraphInputManager,
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is_vmm_pointer,
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)
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from sglang.srt.model_executor.runner_backend_utils.tc_piecewise_cuda_graph import (
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is_in_tc_piecewise_cuda_graph,
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)
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@@ -67,6 +71,12 @@ class CustomAllReduceV2:
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max_pull_blocks=max_pull_blocks,
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max_push_blocks=max_push_blocks,
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)
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self._vmm_graph_input_manager = VmmGraphInputManager(
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obj=self.obj,
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group=self.group,
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rank=self.rank,
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world_size=self.world_size,
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)
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self._post_init_obj()
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self.disabled = False
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log_info_on_rank0(logger, "Custom allreduce v2 initialized successfully")
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@@ -97,10 +107,21 @@ class CustomAllReduceV2:
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yield
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finally:
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self.obj.set_cuda_graph_capture(False)
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# cannot call when graph is capturing
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assert (
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torch.cuda.is_current_stream_capturing() == False
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not torch.cuda.is_current_stream_capturing()
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), "Cannot register graph inputs while capturing CUDA graph"
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raw_ptrs = self.obj.get_graph_capture_ptrs()
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if raw_ptrs and is_vmm_pointer(raw_ptrs[0]):
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self._vmm_graph_input_manager.register_graph_inputs()
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else:
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self._register_graph_inputs_ipc()
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def _register_graph_inputs_ipc(self):
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"""Register graph capture inputs via cudaIpcGetMemHandle.
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This is the fast path for cudaMalloc-backed allocations. Fails
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on VMM pointers (expandable_segments).
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"""
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pairs = self.obj.share_graph_inputs()
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handles = [handle for _, handle in pairs]
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offsets = [offset for offset, _ in pairs]
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@@ -108,7 +129,9 @@ class CustomAllReduceV2:
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offsets_all = self._share_list(offsets)
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result = [list(zip(o, h)) for o, h in zip(offsets_all, handles_all)]
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self.obj.register_inputs(result)
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log_info_on_rank0(logger, f"Registering {len(pairs)} cuda graph addresses")
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log_info_on_rank0(
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logger, f"Registered {len(pairs)} cuda graph addresses via IPC"
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)
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def should_custom_ar(self, inp: torch.Tensor) -> bool:
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"""Check if the input tensor is suitable for custom all-reduce."""
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@@ -134,6 +157,8 @@ class CustomAllReduceV2:
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def close(self):
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if not self.disabled and hasattr(self, "obj"):
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self.obj.free(self.group)
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if hasattr(self, "_vmm_graph_input_manager"):
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self._vmm_graph_input_manager.close()
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def _all_reduce(self, input: torch.Tensor) -> torch.Tensor:
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"""Perform the actual all-reduce via JIT kernel."""
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@@ -0,0 +1,579 @@
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import logging
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import os
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import struct
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import time
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from typing import Any, List, Optional
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import torch
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import torch.distributed as dist
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from torch.distributed import ProcessGroup
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from sglang.srt.utils import log_info_on_rank0
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logger = logging.getLogger(__name__)
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_drv = None
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_FD_HEADER_BYTES = 24
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_FD_SEND_TIMEOUT_S = 120.0
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def _get_cuda_driver():
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"""Lazily import cuda.bindings.driver (cached after first call)."""
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global _drv
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if _drv is None:
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from cuda.bindings import driver
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_drv = driver
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return _drv
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def _check_drv(result_tuple, label):
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"""Check a cuda.bindings driver call result and return the value."""
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if not isinstance(result_tuple, tuple):
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result_tuple = (result_tuple,)
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err = result_tuple[0]
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drv = _get_cuda_driver()
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if err != drv.CUresult.CUDA_SUCCESS:
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raise RuntimeError(f"{label}: {err}")
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return result_tuple[1] if len(result_tuple) > 1 else None
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def is_vmm_pointer(ptr: int) -> bool:
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"""Check if a device pointer is VMM-backed (cuMemCreate/cuMemMap).
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cuMemRetainAllocationHandle succeeds only on pointers from cuMemCreate;
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it fails on cudaMalloc pointers.
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"""
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drv = _get_cuda_driver()
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err, handle = drv.cuMemRetainAllocationHandle(ptr)
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if err == drv.CUresult.CUDA_SUCCESS:
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drv.cuMemRelease(handle)
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return True
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return False
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def _send_fd(sock, fd: int, src_rank: int, base_idx: int) -> None:
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import array
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import socket
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fds = array.array("i", [int(fd)])
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header = struct.pack("<QQQ", int(src_rank), int(base_idx), 1)
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sent = sock.sendmsg(
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[header],
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[(socket.SOL_SOCKET, socket.SCM_RIGHTS, fds.tobytes())],
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)
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if sent != len(header):
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raise RuntimeError(f"sendmsg sent {sent} bytes, expected {len(header)}")
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def _recv_fd(sock):
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import array
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import socket
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fd_item_size = array.array("i").itemsize
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data, ancdata, _, _ = sock.recvmsg(
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_FD_HEADER_BYTES, socket.CMSG_SPACE(fd_item_size)
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)
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if not data:
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return None
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if len(data) != _FD_HEADER_BYTES:
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raise RuntimeError(
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f"received truncated fd header: {len(data)} < {_FD_HEADER_BYTES}"
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)
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src_rank, base_idx, fd_count = struct.unpack("<QQQ", data)
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fds = array.array("i")
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for level, cmsg_type, cmsg_data in ancdata:
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if level == socket.SOL_SOCKET and cmsg_type == socket.SCM_RIGHTS:
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fds.frombytes(cmsg_data[: len(cmsg_data) - (len(cmsg_data) % fd_item_size)])
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if fd_count != 1 or len(fds) != 1:
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for fd in fds:
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os.close(fd)
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raise RuntimeError(
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f"expected one fd, got header={fd_count}, ancillary={len(fds)}"
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)
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return int(src_rank), int(base_idx), int(fds[0])
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class VmmGraphInputManager:
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def __init__(
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self,
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obj: Any,
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group: ProcessGroup,
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rank: int,
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world_size: int,
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) -> None:
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self.obj = obj
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self.group = group
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self.rank = rank
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self.world_size = world_size
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self._peer_mappings = []
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def register_graph_inputs(self):
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"""Register graph capture inputs via VMM handle exchange.
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VMM-compatible path for expandable_segments. The C++ side deduplicates
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graph capture pointers into unique base allocations via cuMemGetAddressRange.
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Python exports handles for each unique base, imports + cuMemMaps peer
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allocations, then registers the peer VAs. FABRIC handles are preferred;
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POSIX file descriptors are used when FABRIC is unavailable.
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"""
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drv = _get_cuda_driver()
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FABRIC = drv.CUmemAllocationHandleType.CU_MEM_HANDLE_TYPE_FABRIC
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POSIX_FD = (
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drv.CUmemAllocationHandleType.CU_MEM_HANDLE_TYPE_POSIX_FILE_DESCRIPTOR
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)
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FABRIC_HANDLE_BYTES = 64
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MAX_VMM_BASES = 4096
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MAX_CHUNKS_PER_INPUT = 16
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t0 = time.perf_counter()
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bases_info, input_chunk_indices, input_offsets = (
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self.obj.get_graph_capture_bases()
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)
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if not bases_info:
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return
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new_count = len(input_chunk_indices)
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num_bases = len(bases_info)
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device_id = torch.cuda.current_device()
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if num_bases > MAX_VMM_BASES:
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raise RuntimeError(
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f"Too many VMM bases to share: {num_bases} > {MAX_VMM_BASES}"
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)
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local_fabric_handles: List[bytes] = []
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local_posix_fds: List[int] = []
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retained_handles = []
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try:
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for base_ptr, _ in bases_info:
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alloc_h = _check_drv(
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drv.cuMemRetainAllocationHandle(base_ptr),
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"cuMemRetainAllocationHandle",
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)
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retained_handles.append(alloc_h)
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local_fabric_error: Optional[Exception] = None
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try:
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for alloc_h in retained_handles:
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fabric_h = _check_drv(
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drv.cuMemExportToShareableHandle(alloc_h, FABRIC, 0),
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"cuMemExportToShareableHandle(FABRIC)",
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)
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local_fabric_handles.append(bytes(fabric_h.data))
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local_fabric_ok = True
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except Exception as e:
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local_fabric_error = e
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local_fabric_ok = False
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local_fabric_handles = []
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logger.info(
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"FABRIC handle export failed on rank %s; falling back to "
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"POSIX fd transport: %s",
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self.rank,
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e,
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)
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use_fabric = self._all_ranks_ok(local_fabric_ok)
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if not use_fabric:
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local_posix_error: Optional[Exception] = None
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try:
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for alloc_h in retained_handles:
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fd = _check_drv(
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drv.cuMemExportToShareableHandle(alloc_h, POSIX_FD, 0),
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"cuMemExportToShareableHandle(POSIX_FD)",
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)
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local_posix_fds.append(int(fd))
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local_posix_ok = True
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except Exception as e:
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local_posix_error = e
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local_posix_ok = False
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for fd in local_posix_fds:
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try:
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os.close(fd)
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except OSError:
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pass
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local_posix_fds = []
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if not self._all_ranks_ok(local_posix_ok):
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local_cause = local_posix_error or local_fabric_error
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message = (
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"VMM graph input registration failed: FABRIC export "
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"failed on at least one rank and POSIX fd export failed "
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"on at least one rank"
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)
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if local_cause is not None:
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message += f"; local rank {self.rank} error: {local_cause}"
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raise RuntimeError(message) from local_posix_error
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local_input_chunks = [
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[int(idx) for idx in indices] for indices in input_chunk_indices
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]
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for chunks in local_input_chunks:
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if len(chunks) > MAX_CHUNKS_PER_INPUT:
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raise RuntimeError(
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"Too many VMM chunks for graph input: "
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f"{len(chunks)} > {MAX_CHUNKS_PER_INPUT}"
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)
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# All-gather base metadata and per-input VMM spans. A captured tensor
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# can cross expandable-segment allocation boundaries, so peer mappings
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# must preserve each input's contiguous virtual-address span. FABRIC
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# handles are inline metadata; POSIX fds are exchanged separately via
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# SCM_RIGHTS because fd integers are process-local.
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header_struct = struct.Struct("<QQ")
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base_struct = struct.Struct(
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f"<QQ{FABRIC_HANDLE_BYTES}s" if use_fabric else "<QQ"
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)
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input_struct = struct.Struct(f"<QQ{MAX_CHUNKS_PER_INPUT}Q")
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base_offset = header_struct.size
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input_offset = base_offset + MAX_VMM_BASES * base_struct.size
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payload_size = input_offset + new_count * input_struct.size
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local_payload = bytearray(payload_size)
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header_struct.pack_into(local_payload, 0, num_bases, new_count)
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for i, (base_ptr, alloc_size) in enumerate(bases_info):
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if use_fabric:
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base_struct.pack_into(
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local_payload,
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base_offset + i * base_struct.size,
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int(base_ptr),
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int(alloc_size),
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local_fabric_handles[i],
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)
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else:
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base_struct.pack_into(
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local_payload,
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base_offset + i * base_struct.size,
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int(base_ptr),
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int(alloc_size),
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)
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for i, (chunks, offset) in enumerate(
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zip(local_input_chunks, input_offsets)
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):
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padded_chunks = chunks + [0] * (MAX_CHUNKS_PER_INPUT - len(chunks))
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input_struct.pack_into(
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local_payload,
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input_offset + i * input_struct.size,
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int(offset),
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len(chunks),
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*padded_chunks,
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)
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in_buf = torch.frombuffer(local_payload, dtype=torch.uint8).clone()
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gather_list = [torch.empty_like(in_buf) for _ in range(self.world_size)]
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dist.all_gather(gather_list, in_buf, group=self.group)
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all_base_payload = []
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all_input_chunks = []
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all_input_offsets = []
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for rank, gathered in enumerate(gather_list):
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payload = gathered.numpy().tobytes()
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peer_num_bases, peer_new_count = header_struct.unpack_from(payload, 0)
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if peer_new_count != new_count:
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raise RuntimeError(
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"Mismatched graph input count across ranks: "
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f"rank {rank} has {peer_new_count}, expected {new_count}"
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)
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peer_bases = []
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for i in range(peer_num_bases):
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if use_fabric:
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base_ptr, alloc_size, fabric_handle = base_struct.unpack_from(
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payload, base_offset + i * base_struct.size
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)
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else:
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base_ptr, alloc_size = base_struct.unpack_from(
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payload, base_offset + i * base_struct.size
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)
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fabric_handle = None
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peer_bases.append((base_ptr, fabric_handle, alloc_size))
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peer_chunks = []
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peer_offsets = []
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for i in range(new_count):
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unpacked = input_struct.unpack_from(
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payload, input_offset + i * input_struct.size
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)
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offset, chunk_count, *chunks = unpacked
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peer_offsets.append(offset)
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peer_chunks.append(list(chunks[:chunk_count]))
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all_base_payload.append(peer_bases)
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all_input_chunks.append(peer_chunks)
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all_input_offsets.append(peer_offsets)
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posix_peer_fds = {}
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if not use_fabric:
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posix_peer_fds = self._exchange_posix_fds(
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local_posix_fds,
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[len(peer_bases) for peer_bases in all_base_payload],
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)
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# Import + map peer allocations. Individual base mappings are kept for
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# single-chunk inputs; span mappings reserve a contiguous VA range and
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# map each chunk at its original relative offset.
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peer_base_va = {} # (rank, base_idx) -> local VA
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peer_span_va = {} # (rank, chunk_indices...) -> (local VA, peer base)
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new_mappings = []
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def import_peer_handle(peer_rank: int, base_idx: int, fabric_handle):
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if use_fabric:
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return _check_drv(
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drv.cuMemImportFromShareableHandle(fabric_handle, FABRIC),
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f"cuMemImportFromShareableHandle(rank={peer_rank})",
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)
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fd = posix_peer_fds[(peer_rank, base_idx)]
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dup_fd = os.dup(fd)
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try:
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return _check_drv(
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drv.cuMemImportFromShareableHandle(dup_fd, POSIX_FD),
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f"cuMemImportFromShareableHandle(rank={peer_rank}, POSIX_FD)",
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)
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finally:
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try:
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os.close(dup_fd)
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except OSError:
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pass
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try:
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for peer_rank in range(self.world_size):
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if peer_rank == self.rank:
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for idx, (bp, _) in enumerate(bases_info):
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peer_base_va[(peer_rank, idx)] = int(bp)
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continue
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peer_bases = all_base_payload[peer_rank]
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for idx, (_, fb, alloc_size) in enumerate(peer_bases):
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imp_h = import_peer_handle(peer_rank, idx, fb)
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prop = _check_drv(
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drv.cuMemGetAllocationPropertiesFromHandle(imp_h),
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"cuMemGetAllocationPropertiesFromHandle",
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)
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gran = _check_drv(
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drv.cuMemGetAllocationGranularity(
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prop,
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drv.CUmemAllocationGranularity_flags.CU_MEM_ALLOC_GRANULARITY_RECOMMENDED,
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),
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"cuMemGetAllocationGranularity",
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)
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va = _check_drv(
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drv.cuMemAddressReserve(alloc_size, int(gran), 0, 0),
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"cuMemAddressReserve",
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)
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_check_drv(
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drv.cuMemMap(int(va), alloc_size, 0, imp_h, 0),
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"cuMemMap",
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)
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access = drv.CUmemAccessDesc()
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access.location.type = (
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drv.CUmemLocationType.CU_MEM_LOCATION_TYPE_DEVICE
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)
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access.location.id = device_id
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access.flags = (
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drv.CUmemAccess_flags.CU_MEM_ACCESS_FLAGS_PROT_READWRITE
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)
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_check_drv(
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drv.cuMemSetAccess(int(va), alloc_size, [access], 1),
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"cuMemSetAccess",
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)
|
||||
peer_base_va[(peer_rank, idx)] = int(va)
|
||||
new_mappings.append((int(va), alloc_size, [(0, alloc_size)]))
|
||||
_check_drv(drv.cuMemRelease(imp_h), "cuMemRelease(peer)")
|
||||
|
||||
# Build per-input peer VA lists and register.
|
||||
peer_ptrs = []
|
||||
for j in range(new_count):
|
||||
ptrs_j = []
|
||||
for rank in range(self.world_size):
|
||||
chunks = all_input_chunks[rank][j]
|
||||
off = all_input_offsets[rank][j]
|
||||
if len(chunks) == 1:
|
||||
ptrs_j.append(peer_base_va[(rank, chunks[0])] + off)
|
||||
continue
|
||||
|
||||
span_key = (rank, *chunks)
|
||||
if span_key not in peer_span_va:
|
||||
peer_bases = all_base_payload[rank]
|
||||
first_base = peer_bases[chunks[0]][0]
|
||||
last_base, _, last_size = peer_bases[chunks[-1]]
|
||||
span_size = (
|
||||
int(last_base) + int(last_size) - int(first_base)
|
||||
)
|
||||
if rank == self.rank:
|
||||
span_va = int(first_base)
|
||||
else:
|
||||
span_va = _check_drv(
|
||||
drv.cuMemAddressReserve(span_size, 0, 0, 0),
|
||||
"cuMemAddressReserve(span)",
|
||||
)
|
||||
mapped_chunks = []
|
||||
for chunk_idx in chunks:
|
||||
base_ptr, fb, alloc_size = peer_bases[chunk_idx]
|
||||
rel = int(base_ptr) - int(first_base)
|
||||
imp_h = import_peer_handle(rank, chunk_idx, fb)
|
||||
_check_drv(
|
||||
drv.cuMemMap(
|
||||
int(span_va) + rel,
|
||||
int(alloc_size),
|
||||
0,
|
||||
imp_h,
|
||||
0,
|
||||
),
|
||||
"cuMemMap(span)",
|
||||
)
|
||||
access = drv.CUmemAccessDesc()
|
||||
access.location.type = (
|
||||
drv.CUmemLocationType.CU_MEM_LOCATION_TYPE_DEVICE
|
||||
)
|
||||
access.location.id = device_id
|
||||
access.flags = (
|
||||
drv.CUmemAccess_flags.CU_MEM_ACCESS_FLAGS_PROT_READWRITE
|
||||
)
|
||||
_check_drv(
|
||||
drv.cuMemSetAccess(
|
||||
int(span_va) + rel,
|
||||
int(alloc_size),
|
||||
[access],
|
||||
1,
|
||||
),
|
||||
"cuMemSetAccess(span)",
|
||||
)
|
||||
mapped_chunks.append((rel, int(alloc_size)))
|
||||
_check_drv(
|
||||
drv.cuMemRelease(imp_h), "cuMemRelease(span)"
|
||||
)
|
||||
new_mappings.append(
|
||||
(int(span_va), span_size, mapped_chunks)
|
||||
)
|
||||
peer_span_va[span_key] = (int(span_va), int(first_base))
|
||||
|
||||
span_va, _ = peer_span_va[span_key]
|
||||
ptrs_j.append(span_va + off)
|
||||
peer_ptrs.append(ptrs_j)
|
||||
|
||||
self.obj.register_peer_mapped_inputs(peer_ptrs)
|
||||
self._peer_mappings.extend(new_mappings)
|
||||
except Exception:
|
||||
self._release_peer_mappings(new_mappings)
|
||||
raise
|
||||
finally:
|
||||
for fd in posix_peer_fds.values():
|
||||
os.close(fd)
|
||||
|
||||
elapsed_ms = (time.perf_counter() - t0) * 1000
|
||||
transport = "FABRIC" if use_fabric else "POSIX fd"
|
||||
log_info_on_rank0(
|
||||
logger,
|
||||
f"Registered {new_count} cuda graph addresses via "
|
||||
f"{transport} handles ({num_bases} unique allocations) "
|
||||
f"in {elapsed_ms:.1f} ms",
|
||||
)
|
||||
finally:
|
||||
for fd in local_posix_fds:
|
||||
os.close(fd)
|
||||
for h in retained_handles:
|
||||
_check_drv(drv.cuMemRelease(h), "cuMemRelease(retained)")
|
||||
|
||||
def close(self):
|
||||
if not self._peer_mappings:
|
||||
return
|
||||
self._release_peer_mappings(self._peer_mappings)
|
||||
|
||||
def _all_ranks_ok(self, ok: bool) -> bool:
|
||||
flag = torch.tensor([1 if ok else 0], dtype=torch.int32)
|
||||
dist.all_reduce(flag, op=dist.ReduceOp.BAND, group=self.group)
|
||||
return flag.item() == 1
|
||||
|
||||
def _exchange_posix_fds(self, local_fds: List[int], peer_base_counts: List[int]):
|
||||
import socket
|
||||
import tempfile
|
||||
import threading
|
||||
|
||||
sock_kind = getattr(socket, "SOCK_SEQPACKET", socket.SOCK_STREAM)
|
||||
sock_dir = tempfile.mkdtemp(prefix="sgl_ar_fd_")
|
||||
sock_path = os.path.join(sock_dir, f"rank_{self.rank}.sock")
|
||||
server = socket.socket(socket.AF_UNIX, sock_kind)
|
||||
server.settimeout(_FD_SEND_TIMEOUT_S)
|
||||
received_fds = {}
|
||||
errors = []
|
||||
|
||||
def recv_loop():
|
||||
try:
|
||||
for _ in range(self.world_size - 1):
|
||||
conn, _ = server.accept()
|
||||
with conn:
|
||||
conn.settimeout(_FD_SEND_TIMEOUT_S)
|
||||
while True:
|
||||
packet = _recv_fd(conn)
|
||||
if packet is None:
|
||||
break
|
||||
src_rank, base_idx, fd = packet
|
||||
key = (src_rank, base_idx)
|
||||
if key in received_fds:
|
||||
os.close(fd)
|
||||
raise RuntimeError(f"duplicate fd for {key}")
|
||||
received_fds[key] = fd
|
||||
except BaseException as e:
|
||||
errors.append(e)
|
||||
|
||||
try:
|
||||
server.bind(sock_path)
|
||||
server.listen(self.world_size)
|
||||
paths = [None] * self.world_size
|
||||
dist.all_gather_object(paths, sock_path, group=self.group)
|
||||
|
||||
thread = threading.Thread(target=recv_loop, daemon=True)
|
||||
thread.start()
|
||||
try:
|
||||
for peer_rank, peer_path in enumerate(paths):
|
||||
if peer_rank == self.rank:
|
||||
continue
|
||||
with socket.socket(socket.AF_UNIX, sock_kind) as sock:
|
||||
sock.settimeout(_FD_SEND_TIMEOUT_S)
|
||||
sock.connect(peer_path)
|
||||
for base_idx, fd in enumerate(local_fds):
|
||||
_send_fd(sock, fd, self.rank, base_idx)
|
||||
finally:
|
||||
thread.join(_FD_SEND_TIMEOUT_S)
|
||||
|
||||
if thread.is_alive():
|
||||
raise RuntimeError("timed out waiting for POSIX fd exchange")
|
||||
if errors:
|
||||
raise RuntimeError("POSIX fd exchange receive failed") from errors[0]
|
||||
|
||||
expected = {
|
||||
(rank, base_idx)
|
||||
for rank, count in enumerate(peer_base_counts)
|
||||
if rank != self.rank
|
||||
for base_idx in range(count)
|
||||
}
|
||||
missing = expected.difference(received_fds)
|
||||
extra = set(received_fds).difference(expected)
|
||||
if missing or extra:
|
||||
for fd in received_fds.values():
|
||||
os.close(fd)
|
||||
raise RuntimeError(
|
||||
"POSIX fd exchange mismatch: "
|
||||
f"missing={sorted(missing)[:8]}, extra={sorted(extra)[:8]}"
|
||||
)
|
||||
return received_fds
|
||||
finally:
|
||||
server.close()
|
||||
try:
|
||||
os.unlink(sock_path)
|
||||
except FileNotFoundError:
|
||||
pass
|
||||
try:
|
||||
os.rmdir(sock_dir)
|
||||
except OSError:
|
||||
pass
|
||||
|
||||
def _release_peer_mappings(self, mappings):
|
||||
drv = _get_cuda_driver()
|
||||
while mappings:
|
||||
va, span_size, mapped_chunks = mappings.pop()
|
||||
for rel, size in mapped_chunks:
|
||||
_check_drv(drv.cuMemUnmap(int(va) + int(rel), int(size)), "cuMemUnmap")
|
||||
_check_drv(
|
||||
drv.cuMemAddressFree(int(va), int(span_size)), "cuMemAddressFree"
|
||||
)
|
||||
Reference in New Issue
Block a user