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617 lines
26 KiB
Python
617 lines
26 KiB
Python
# SPDX-License-Identifier: Apache-2.0
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"""Attention backend utils"""
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from collections import defaultdict
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from contextlib import contextmanager
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from itertools import accumulate
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from typing import TYPE_CHECKING, Any, Dict, List, Tuple, Type, TypeVar, Union
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import numpy as np
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import torch
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from vllm import envs
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from vllm.attention import (AttentionMetadata, AttentionMetadataBuilder,
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AttentionState)
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from vllm.attention.backends.abstract import AttentionType
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from vllm.logger import logging
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from vllm.multimodal import MultiModalPlaceholderMap
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from vllm.platforms import current_platform
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from vllm.utils import async_tensor_h2d, make_tensor_with_pad
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logger = logging.getLogger(__name__)
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if TYPE_CHECKING:
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from vllm.worker.model_runner_base import ModelRunnerBase
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# Error string(s) for encoder/decoder
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# unsupported attention scenarios
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STR_NOT_IMPL_ENC_DEC_ROCM_HIP = ("ROCm/HIP is not currently supported "
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"with encoder/decoder models.")
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PAD_SLOT_ID = -1
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# Switch to numpy implementation of compute_slot_mapping
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# if we have at least this many elements. Could be tuned further.
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_COMPUTE_SLOT_MAPPING_NUMPY_NUMEL = 256
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if TYPE_CHECKING:
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from vllm.worker.model_runner import ModelInputForGPUBuilder
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def is_block_tables_empty(block_tables: Union[None, Dict]):
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"""
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Check if block_tables is None or a dictionary with all None values.
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"""
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if block_tables is None:
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return True
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return (isinstance(block_tables, dict)
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and all(value is None for value in block_tables.values()))
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def compute_slot_mapping_start_idx(is_prompt: bool, query_len: int,
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context_len: int, sliding_window: int):
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"""
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Compute the start index of slot mapping.
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"""
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start_idx = 0
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if is_prompt and sliding_window is not None:
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start_idx = max(0, query_len - sliding_window)
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return start_idx
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def _compute_slot_mapping_python(slot_mapping: List[int],
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block_table: List[int], range_start: int,
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range_end: int, block_size: int):
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for i in range(range_start, range_end):
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block_number = block_table[i // block_size]
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block_offset = i % block_size
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slot = block_number * block_size + block_offset
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slot_mapping.append(slot)
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def _compute_slot_mapping_numpy(slot_mapping: List[int],
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block_table: List[int], range_start: int,
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range_end: int, block_size: int):
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block_table_array = np.array(block_table)
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idx = np.arange(range_start, range_end)
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block_offset = idx % block_size
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idx //= block_size
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seq_slot_mapping_array = block_table_array[idx]
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seq_slot_mapping_array *= block_size
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seq_slot_mapping_array += block_offset
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slot_mapping.extend(seq_slot_mapping_array)
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def compute_slot_mapping(is_profile_run: bool, slot_mapping: List[int],
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seq_id: int, seq_len: int, context_len: int,
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start_idx: int, block_size: int,
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block_tables: Dict[int, List[int]]):
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"""
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Compute slot mapping.
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"""
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if is_profile_run:
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# During memory profiling, the block tables are not
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# initialized yet. In this case, we just use a dummy
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# slot mapping.
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# In embeddings, the block tables are {seq_id: None}.
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slot_mapping.extend([PAD_SLOT_ID] * seq_len)
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return
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# Mask the [0, start_idx) tokens of the prompt with
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# PAD_SLOT_ID, where start_idx is max(0, seq_len -
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# sliding_window). For example, if the prompt len is 10,
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# sliding window is 8, and block size is 4, the first two
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# tokens are masked and the slot mapping will be
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# [-1, -1, 2, 3, 4, 5, 6, 7, 0, 1].
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padding_mask_len = max(0, start_idx - context_len)
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slot_mapping.extend([PAD_SLOT_ID] * padding_mask_len)
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range_start = max(start_idx, context_len)
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range_end = seq_len
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numel = range_end - range_start
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block_table = block_tables[seq_id]
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# numpy implementation will be faster than python if we have
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# many elements, otherwise it will be slower.
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if numel < _COMPUTE_SLOT_MAPPING_NUMPY_NUMEL:
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_compute_slot_mapping_python(slot_mapping, block_table, range_start,
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range_end, block_size)
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else:
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_compute_slot_mapping_numpy(slot_mapping, block_table, range_start,
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range_end, block_size)
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TAttentionMetadata = TypeVar("TAttentionMetadata", bound='AttentionMetadata')
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class CommonMetadataBuilder(AttentionMetadataBuilder[TAttentionMetadata]):
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_metadata_cls: Type[TAttentionMetadata]
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def __init__(self, input_builder: "ModelInputForGPUBuilder"):
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self.input_builder = input_builder
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self.runner = input_builder.runner
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self.sliding_window = input_builder.sliding_window
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self.block_size = input_builder.block_size
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def prepare(self):
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self.slot_mapping: List[int] = []
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self.prefill_seq_lens: List[int] = []
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self.context_lens: List[int] = []
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self.block_tables: List[List[int]] = []
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self.curr_seq_lens: List[int] = []
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self.multimodal_placeholder_maps: Dict[
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str,
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MultiModalPlaceholderMap] = defaultdict(MultiModalPlaceholderMap)
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self.num_prefills = 0
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self.num_prefill_tokens = 0
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self.num_decode_tokens = 0
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def _add_seq_group(
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self, inter_data: "ModelInputForGPUBuilder.InterDataForSeqGroup",
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chunked_prefill_enabled: bool):
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is_prompt = inter_data.is_prompt
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block_tables = inter_data.block_tables
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for (seq_id, token_len, seq_len, curr_seq_len, query_len, context_len,
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curr_sliding_window_block) in zip(
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inter_data.seq_ids, [len(t) for t in inter_data.input_tokens],
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inter_data.orig_seq_lens, inter_data.seq_lens,
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inter_data.query_lens, inter_data.context_lens,
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inter_data.curr_sliding_window_blocks):
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self.context_lens.append(context_len)
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if is_prompt:
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mm_maps = inter_data.multi_modal_placeholder_maps
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if mm_maps:
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for modality, placeholders in mm_maps.items():
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self.multimodal_placeholder_maps[modality].extend(
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placeholders)
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self.num_prefills += 1
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self.num_prefill_tokens += token_len
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self.prefill_seq_lens.append(seq_len)
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else:
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assert query_len == 1, (
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"seq_len: {}, context_len: {}, query_len: {}".format(
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seq_len, context_len, query_len))
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self.num_decode_tokens += query_len
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self.curr_seq_lens.append(curr_seq_len)
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# Compute block table.
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# TODO(sang): Combine chunked prefill and prefix caching by
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# only allowing multiple of block_size chunk size.
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# NOTE: This only works for oooooooxxx style attention.
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block_table = []
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if inter_data.prefix_cache_hit:
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block_table = block_tables[seq_id]
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elif ((chunked_prefill_enabled or not is_prompt)
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and block_tables is not None):
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if curr_sliding_window_block == 0:
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block_table = block_tables[seq_id]
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else:
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block_table = block_tables[seq_id][
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-curr_sliding_window_block:]
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self.block_tables.append(block_table)
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# Compute slot mapping.
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is_profile_run = is_block_tables_empty(block_tables)
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start_idx = compute_slot_mapping_start_idx(is_prompt, query_len,
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context_len,
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self.sliding_window)
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compute_slot_mapping(is_profile_run, self.slot_mapping, seq_id,
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seq_len, context_len, start_idx,
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self.block_size, inter_data.block_tables)
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def build(self, seq_lens: List[int], query_lens: List[int],
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cuda_graph_pad_size: int, batch_size: int):
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"""Build attention metadata with on-device tensors.
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Args:
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seq_lens: The maybe padded sequence lengths of the input sequences.
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query_lens: The query lengths of the input sequences.
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cuda_graph_pad_size: The padding size for cuda graph.
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-1 if cuda graph is not used.
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batch_size: The maybe padded batch size.
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"""
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for inter_data in self.input_builder.inter_data_list:
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self._add_seq_group(inter_data,
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self.input_builder.chunked_prefill_enabled)
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device = self.runner.device
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use_captured_graph = cuda_graph_pad_size != -1
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max_query_len = max(query_lens)
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max_prefill_seq_len = max(self.prefill_seq_lens, default=0)
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max_decode_seq_len = max(self.curr_seq_lens, default=0)
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num_decode_tokens = self.num_decode_tokens
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query_start_loc = list(accumulate(query_lens, initial=0))
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seq_start_loc = list(accumulate(seq_lens, initial=0))
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if use_captured_graph:
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self.slot_mapping.extend([PAD_SLOT_ID] * cuda_graph_pad_size)
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self.block_tables.extend([] * cuda_graph_pad_size)
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num_decode_tokens = batch_size
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# The shape of graph_block_tables is
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# [max batch size, max context len // block size].
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input_block_tables = self.runner.graph_block_tables[:batch_size]
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for i, block_table in enumerate(self.block_tables):
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if block_table:
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input_block_tables[i, :len(block_table)] = block_table
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block_tables = torch.from_numpy(input_block_tables).to(
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device, non_blocking=True)
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else:
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block_tables = make_tensor_with_pad(
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self.block_tables,
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pad=0,
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dtype=torch.int,
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device=device,
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)
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assert max_query_len > 0, "query_lens: {}".format(query_lens)
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assert device is not None
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context_lens_tensor = async_tensor_h2d(self.context_lens, torch.int,
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device, self.runner.pin_memory)
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seq_lens_tensor = async_tensor_h2d(seq_lens, torch.int, device,
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self.runner.pin_memory)
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slot_mapping_tensor = async_tensor_h2d(self.slot_mapping, torch.long,
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device, self.runner.pin_memory)
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query_start_loc_tensor = async_tensor_h2d(query_start_loc, torch.int32,
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device,
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self.runner.pin_memory)
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seq_start_loc_tensor = async_tensor_h2d(seq_start_loc, torch.int32,
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device, self.runner.pin_memory)
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placeholder_index_maps = {
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modality: placeholder_map.index_map()
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for modality, placeholder_map in
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self.multimodal_placeholder_maps.items()
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}
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return self._metadata_cls( # type: ignore
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num_prefills=self.num_prefills,
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slot_mapping=slot_mapping_tensor,
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multi_modal_placeholder_index_maps=placeholder_index_maps,
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enable_kv_scales_calculation=True,
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num_prefill_tokens=self.num_prefill_tokens,
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num_decode_tokens=num_decode_tokens,
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seq_lens=seq_lens,
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seq_lens_tensor=seq_lens_tensor,
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max_query_len=max_query_len,
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max_prefill_seq_len=max_prefill_seq_len,
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max_decode_seq_len=max_decode_seq_len,
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query_start_loc=query_start_loc_tensor,
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seq_start_loc=seq_start_loc_tensor,
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context_lens_tensor=context_lens_tensor,
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block_tables=block_tables,
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use_cuda_graph=use_captured_graph,
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)
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class CommonAttentionState(AttentionState):
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def __init__(self, runner: "ModelRunnerBase"):
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self.runner = runner
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self._is_graph_capturing = False
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@contextmanager
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def graph_capture(self, max_batch_size: int):
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self._is_graph_capturing = True
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self._graph_slot_mapping = torch.full((max_batch_size, ),
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PAD_SLOT_ID,
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dtype=torch.long,
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device=self.runner.device)
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self._graph_seq_lens = torch.ones(max_batch_size,
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dtype=torch.int32,
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device=self.runner.device)
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self._graph_block_tables = torch.from_numpy(
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self.runner.graph_block_tables).to(device=self.runner.device)
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yield
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self._is_graph_capturing = False
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del self._graph_slot_mapping
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del self._graph_seq_lens
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del self._graph_block_tables
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def graph_clone(self, batch_size: int) -> "CommonAttentionState":
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assert self._is_graph_capturing
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return self.__class__(self.runner)
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def graph_capture_get_metadata_for_batch(
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self, batch_size: int, is_encoder_decoder_model: bool = False):
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assert self._is_graph_capturing
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attn_metadata = self.runner.attn_backend.make_metadata(
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num_prefills=0,
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num_prefill_tokens=0,
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num_decode_tokens=batch_size,
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slot_mapping=self._graph_slot_mapping[:batch_size],
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multi_modal_placeholder_index_maps=None,
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enable_kv_scales_calculation=True,
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seq_lens=None,
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seq_lens_tensor=self._graph_seq_lens[:batch_size],
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max_query_len=1,
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max_decode_query_len=1,
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max_prefill_seq_len=0,
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max_decode_seq_len=self.runner.max_seq_len_to_capture,
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query_start_loc=None,
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seq_start_loc=None,
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context_lens_tensor=None,
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block_tables=self._graph_block_tables[:batch_size],
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use_cuda_graph=True,
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)
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if is_encoder_decoder_model:
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# The encoder decoder model works only with XFormers and
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# Flash Attention backend. Assert the same.
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assert self.runner.attn_backend.get_name() in\
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["XFORMERS", "FLASH_ATTN"], \
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f"Expected attn_backend name to be either 'XFORMERS' or " \
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f"'FLASH_ATTN', but "\
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f"got '{self.runner.attn_backend.get_name()}'"
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self._update_captured_metadata_for_enc_dec_model(
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batch_size=batch_size, attn_metadata=attn_metadata)
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return attn_metadata
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def get_graph_input_buffers(
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self,
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attn_metadata,
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is_encoder_decoder_model: bool = False) -> Dict[str, Any]:
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input_buffers = {
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"slot_mapping": attn_metadata.slot_mapping,
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"seq_lens_tensor": attn_metadata.decode_metadata.seq_lens_tensor,
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"block_tables": attn_metadata.decode_metadata.block_tables,
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}
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if is_encoder_decoder_model:
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# The encoder decoder model works only with XFormers and
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# Flash Attention backend. Assert the same.
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assert self.runner.attn_backend.get_name() in\
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["XFORMERS", "FLASH_ATTN"], \
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f"Expected attn_backend name to be either 'XFORMERS' or "\
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f"'FLASH_ATTN', but "\
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f"got '{self.runner.attn_backend.get_name()}'"
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self._add_additonal_input_buffers_for_enc_dec_model(
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attn_metadata=attn_metadata, input_buffers=input_buffers)
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return input_buffers
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def prepare_graph_input_buffers(
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self,
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input_buffers,
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attn_metadata,
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is_encoder_decoder_model: bool = False) -> None:
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input_buffers["seq_lens_tensor"].copy_(
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attn_metadata.decode_metadata.seq_lens_tensor, non_blocking=True)
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input_buffers["block_tables"].copy_(
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attn_metadata.decode_metadata.block_tables, non_blocking=True)
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if is_encoder_decoder_model:
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# The encoder decoder model works only with XFormers and
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# Flash Attention backend. Assert the same.
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assert self.runner.attn_backend.get_name() in\
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["XFORMERS", "FLASH_ATTN"], \
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f"Expected attn_backend name to be either 'XFORMERS' or "\
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f"'FLASH_ATTN', but "\
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f"got '{self.runner.attn_backend.get_name()}'"
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self._prepare_input_buffers_for_enc_dec_model(
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attn_metadata, input_buffers)
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def begin_forward(self, model_input) -> None:
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return
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def _update_captured_metadata_for_enc_dec_model(self, batch_size: int,
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attn_metadata):
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"""
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Updates the attention metadata parameters for CUDA graph capture in an
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encoder-decoder model.
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This method modifies attention-related tensors and metadata required
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for CUDA graph capture in encoder-decoder models. Specifically, it
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updates the cross-attention and encoder sequence tensors in the
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AttentionMetadata object.
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"""
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# During decode phase the cross_slot_mapping will be empty. Hence set
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# an empty tensor for CUDA Graph capture.
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attn_metadata.cross_slot_mapping = torch.tensor(
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[], dtype=torch.int).cuda()
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attn_metadata.cross_block_tables = torch.full(
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(batch_size, self.runner.get_max_block_per_batch()),
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1,
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dtype=torch.int).cuda()
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attn_metadata.encoder_seq_lens = torch.full((batch_size, ),
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1,
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dtype=torch.int).cuda()
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attn_metadata.encoder_seq_lens_tensor = torch.full(
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(batch_size, ), 1, dtype=torch.int).cuda()
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attn_metadata.max_encoder_seq_len = self.runner.max_seq_len_to_capture
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attn_metadata.num_encoder_tokens = 0
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def _add_additonal_input_buffers_for_enc_dec_model(
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self, attn_metadata, input_buffers: Dict[str, Any]):
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"""
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Saves additional input buffers specific to the encoder-decoder model
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from the attention metadata.
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This method extracts and stores encoder-decoder related input buffers
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from the `attn_metadata` into the `input_buffers` dictionary. The
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buffers include encoder sequence lengths, cross-slot mappings, and
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cross-block tables, which are essential for the encoder-decoder model
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during CUDA graph replay.
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"""
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input_buffers["encoder_seq_lens_tensor"] = (
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attn_metadata.decode_metadata.encoder_seq_lens_tensor)
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input_buffers["cross_slot_mapping"] = (
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attn_metadata.decode_metadata.cross_slot_mapping)
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input_buffers["cross_block_tables"] = (
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attn_metadata.decode_metadata.cross_block_tables)
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def _prepare_input_buffers_for_enc_dec_model(self, attn_metadata,
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input_buffers: Dict[str,
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Any]):
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"""
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|
Populates input buffers with data from the encoder-decoder model's
|
|
attention metadata.
|
|
|
|
This method fills the input buffers with encoder-decoder specific
|
|
tensors. It copies data from the `attn_metadata` and keyword arguments
|
|
(`kwargs`) into corresponding buffers in the `input_buffers` dictionary.
|
|
The copied data includes attention-related metadata as well as input
|
|
IDs and positional information for the encoder.
|
|
"""
|
|
input_buffers["encoder_seq_lens_tensor"].copy_(
|
|
attn_metadata.decode_metadata.encoder_seq_lens_tensor,
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|
non_blocking=True)
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|
input_buffers["cross_slot_mapping"].copy_(
|
|
attn_metadata.decode_metadata.cross_slot_mapping,
|
|
non_blocking=True)
|
|
input_buffers["cross_block_tables"].copy_(
|
|
attn_metadata.decode_metadata.cross_block_tables,
|
|
non_blocking=True)
|
|
|
|
|
|
def is_all_encoder_attn_metadata_set(attn_metadata):
|
|
'''
|
|
All attention metadata required for encoder attention is set.
|
|
'''
|
|
return ((attn_metadata.encoder_seq_lens is not None)
|
|
and (attn_metadata.encoder_seq_lens_tensor is not None)
|
|
and (attn_metadata.max_encoder_seq_len is not None))
|
|
|
|
|
|
def is_all_cross_attn_metadata_set(attn_metadata):
|
|
'''
|
|
All attention metadata required for enc/dec cross-attention is set.
|
|
|
|
Superset of encoder attention required metadata.
|
|
'''
|
|
return (attn_metadata.is_all_encoder_attn_metadata_set
|
|
and (attn_metadata.cross_slot_mapping is not None)
|
|
and (attn_metadata.cross_block_tables is not None))
|
|
|
|
|
|
def get_seq_len_block_table_args(
|
|
attn_metadata,
|
|
is_prompt: bool,
|
|
attn_type: str,
|
|
) -> tuple:
|
|
'''
|
|
The particular choice of sequence-length- and block-table-related
|
|
attributes which should be extracted from attn_metadata is dependent
|
|
on the type of attention operation.
|
|
|
|
Decoder attn -> select entirely decoder self-attention-related fields
|
|
Encoder/decoder cross-attn -> select encoder sequence lengths &
|
|
cross-attn block-tables fields
|
|
Encoder attn -> select encoder sequence lengths fields & no block tables
|
|
|
|
Arguments:
|
|
|
|
* attn_metadata: Attention metadata structure associated with attention op
|
|
* is_prompt: True if prefill, False otherwise
|
|
* attn_type: encoder attention, decoder self-attention,
|
|
encoder/decoder cross-attention
|
|
|
|
Returns:
|
|
|
|
* Appropriate sequence-lengths tensor
|
|
* Appropriate max sequence-length scalar
|
|
* Appropriate block tables (or None)
|
|
'''
|
|
|
|
if attn_type == AttentionType.DECODER:
|
|
# Decoder self-attention
|
|
# Choose max_seq_len based on whether we are in prompt_run
|
|
if is_prompt:
|
|
max_seq_len = attn_metadata.max_prefill_seq_len
|
|
else:
|
|
max_seq_len = attn_metadata.max_decode_seq_len
|
|
return (attn_metadata.seq_lens_tensor, max_seq_len,
|
|
attn_metadata.block_tables)
|
|
elif attn_type == AttentionType.ENCODER_DECODER:
|
|
# Enc/dec cross-attention KVs match encoder sequence length;
|
|
# cross-attention utilizes special "cross" block tables
|
|
return (attn_metadata.encoder_seq_lens_tensor,
|
|
attn_metadata.max_encoder_seq_len,
|
|
attn_metadata.cross_block_tables)
|
|
elif attn_type == AttentionType.ENCODER:
|
|
# No block tables associated with encoder attention
|
|
return (attn_metadata.encoder_seq_lens_tensor,
|
|
attn_metadata.max_encoder_seq_len, None)
|
|
else:
|
|
raise AttributeError(f"Invalid attention type {str(attn_type)}")
|
|
|
|
|
|
def get_num_prefill_decode_query_kv_tokens(
|
|
attn_metadata,
|
|
attn_type: str,
|
|
) -> Tuple[int, int, int]:
|
|
"""
|
|
Calculate the number of prefill and decode tokens for query, key/value
|
|
based on the attention metadata and the specified attention type.
|
|
|
|
Args:
|
|
attn_metadata (FlashAttentionMetadata): Attention Metadata object.
|
|
attn_type (AttentionType): The type of attention being used.
|
|
Returns:
|
|
Tuple[int, int, int]: A tuple containing three integers:
|
|
- The number of prefill query tokens.
|
|
- The number of prefill key/value tokens.
|
|
- The number of decode query tokens.
|
|
|
|
Raises:
|
|
AssertionError: If the number of encoder tokens in `attn_metadata`
|
|
is `None` when required for the calculations.
|
|
"""
|
|
num_prefill_query_tokens = 0
|
|
num_decode_query_tokens = 0
|
|
num_prefill_kv_tokens = 0
|
|
if attn_type == AttentionType.ENCODER:
|
|
# Encoder attention is only invoked during prefill phase.
|
|
# The same input servers a both query and key.
|
|
assert attn_metadata.num_encoder_tokens is not None
|
|
num_prefill_query_tokens = attn_metadata.num_encoder_tokens
|
|
num_prefill_kv_tokens = attn_metadata.num_encoder_tokens
|
|
num_decode_query_tokens = 0
|
|
elif attn_type == AttentionType.ENCODER_DECODER:
|
|
assert attn_metadata.num_encoder_tokens is not None
|
|
num_prefill_query_tokens = attn_metadata.num_prefill_tokens
|
|
# The key is the encoder/cross-attention.
|
|
num_prefill_kv_tokens = attn_metadata.num_encoder_tokens
|
|
num_decode_query_tokens = attn_metadata.num_decode_tokens
|
|
else: # attn_type == AttentionType.DECODER or
|
|
# attn_type == AttentionType.ENCODER_ONLY
|
|
num_prefill_query_tokens = attn_metadata.num_prefill_tokens
|
|
num_prefill_kv_tokens = attn_metadata.num_prefill_tokens
|
|
num_decode_query_tokens = attn_metadata.num_decode_tokens
|
|
|
|
return (num_prefill_query_tokens, num_prefill_kv_tokens,
|
|
num_decode_query_tokens)
|
|
|
|
|
|
try:
|
|
from vllm.vllm_flash_attn.flash_attn_interface import (
|
|
fa_version_unsupported_reason, is_fa_version_supported)
|
|
|
|
def flash_attn_version():
|
|
# if hopper default to FA3, otherwise stick to FA2 for now
|
|
# TODO(lucas): profile FA3 on ampere to see if it makes sense to
|
|
# use FA3 as default for both
|
|
if current_platform.get_device_capability()[0] >= 9:
|
|
fa_version = 3 if is_fa_version_supported(3) else 2
|
|
else:
|
|
fa_version = 2
|
|
|
|
if envs.VLLM_FLASH_ATTN_VERSION is not None:
|
|
assert envs.VLLM_FLASH_ATTN_VERSION in [2, 3]
|
|
fa_version = envs.VLLM_FLASH_ATTN_VERSION
|
|
|
|
if not is_fa_version_supported(fa_version):
|
|
logger.error("Cannot use FA version %d is not supported due to %s",
|
|
fa_version, fa_version_unsupported_reason(fa_version))
|
|
|
|
assert is_fa_version_supported(fa_version)
|
|
return fa_version
|
|
|
|
VLLM_FLASH_ATTN_VERSION = flash_attn_version()
|
|
except ImportError:
|
|
VLLM_FLASH_ATTN_VERSION = None
|