319 lines
11 KiB
Python
319 lines
11 KiB
Python
from typing import Dict, FrozenSet, Iterable, List, Optional, Set
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from vllm.core.block.common import (CopyOnWriteTracker, RefCounter,
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get_all_blocks_recursively)
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from vllm.core.block.interfaces import Block, BlockAllocator, BlockId, Device
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Refcount = int
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class NaiveBlockAllocator(BlockAllocator):
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"""A simple block allocator that manages blocks of memory without prefix
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caching.
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Args:
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create_block (Block.Factory): A factory function for creating new
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blocks. This is used when a NaiveBlockAllocator is composed within
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a prefix caching allocator -- the naive block allocator must
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construct prefix caching blocks (but shouldn't know anything else
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about them).
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num_blocks (int): The total number of blocks to manage.
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block_size (int): The size of each block in tokens.
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block_ids (Optional[Iterable[int]], optional): An optional iterable of
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block IDs. If not provided, block IDs will be assigned sequentially
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from 0 to num_blocks - 1.
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"""
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def __init__(
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self,
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create_block: Block.Factory,
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num_blocks: int,
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block_size: int,
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block_ids: Optional[Iterable[int]] = None,
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):
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if block_ids is None:
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block_ids = range(num_blocks)
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self._free_block_indices: Set[BlockId] = set(block_ids)
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self._all_block_indices = frozenset(block_ids)
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assert len(self._all_block_indices) == num_blocks
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self._refcounter = RefCounter(
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all_block_indices=self._free_block_indices)
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self._create_block = create_block
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self._block_size = block_size
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self._cow_tracker = CopyOnWriteTracker(
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refcounter=self._refcounter.as_readonly(),
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allocator=self,
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)
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def allocate_immutable(self,
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prev_block: Optional[Block],
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token_ids: List[int],
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device: Optional[Device] = None) -> Block:
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"""Allocates a new immutable block with the given token IDs, linked to
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the previous block.
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Args:
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prev_block (Optional[Block]): The previous block in the sequence. If
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None, then the block to be allocated is the first block in the
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sequence.
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token_ids (List[int]): The token IDs to be stored in the new block.
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Returns:
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Block: The newly allocated immutable block.
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"""
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assert device is None
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block = self.allocate_mutable(prev_block=prev_block)
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block.append_token_ids(token_ids)
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return block
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def allocate_mutable(self,
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prev_block: Optional[Block],
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device: Optional[Device] = None) -> Block:
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"""Allocates a new mutable block, linked to the previous block.
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Args:
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prev_block (Optional[Block]): The previous block in the sequence. If
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None, then the block to be allocated is the first block in the
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sequence.
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Returns:
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Block: The newly allocated mutable block.
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"""
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assert device is None
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block_id = self._allocate_new_block_id()
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return self._create_block(
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prev_block=prev_block,
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token_ids=[],
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block_id=block_id,
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block_size=self._block_size,
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allocator=self,
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)
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def free(self, block: Block) -> None:
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assert block.block_id is not None
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self._free_block_id(block.block_id)
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# Mark the block as having no allocation.
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block.block_id = None
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def fork(self, last_block: Block) -> List[Block]:
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"""Creates a new sequence of blocks that shares the same underlying
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memory as the original sequence.
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Args:
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last_block (Block): The last block in the original sequence.
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Returns:
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List[Block]: The new sequence of blocks that shares the same memory
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as the original sequence.
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"""
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source_blocks = get_all_blocks_recursively(last_block)
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forked_blocks = []
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prev_block = None
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for block in source_blocks:
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# Increment refcount for each block.
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assert block.block_id is not None
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refcount = self._refcounter.incr(block.block_id)
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assert refcount != 1, "can't fork free'd block"
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forked_blocks.append(
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self._create_block(
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prev_block=prev_block,
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token_ids=block.token_ids,
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block_id=block.block_id,
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block_size=self._block_size,
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allocator=self,
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))
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prev_block = forked_blocks[-1]
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return forked_blocks
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def get_num_free_blocks(self) -> int:
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return len(self._free_block_indices)
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def get_num_total_blocks(self) -> int:
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return len(self._all_block_indices)
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def _allocate_new_block_id(self) -> BlockId:
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if not self._free_block_indices:
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raise BlockAllocator.NoFreeBlocksError()
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block_id = next(iter(self._free_block_indices))
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self._refcounter.incr(block_id)
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self._free_block_indices.remove(block_id)
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return block_id
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def _free_block_id(self, block_id: BlockId) -> None:
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refcount = self._refcounter.decr(block_id)
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if refcount == 0:
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self._free_block_indices.add(block_id)
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@property
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def refcounter(self):
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return self._refcounter
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@property
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def all_block_ids(self) -> FrozenSet[int]:
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return self._all_block_indices
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def cow_block_if_not_appendable(self, block: Block) -> Optional[BlockId]:
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"""Performs a copy-on-write operation on the given block if it is not
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appendable.
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Args:
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block (Block): The block to check for copy-on-write.
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Returns:
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Optional[BlockId]: The block index of the new block if a copy-on
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-write operation was performed, or the original block index if
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no copy-on-write was necessary.
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"""
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return self._cow_tracker.cow_block_if_not_appendable(block)
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def clear_copy_on_writes(self) -> Dict[BlockId, List[BlockId]]:
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"""Returns the copy-on-write source->destination mapping and clears it.
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Returns:
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Dict[BlockId, List[BlockId]]: A dictionary mapping source
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block indices to lists of destination block indices.
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"""
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return self._cow_tracker.clear_cows()
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def mark_blocks_as_accessed(self, block_ids: List[int],
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now: float) -> None:
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"""Mark blocks as accessed, used in prefix caching.
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Since the naive allocator does not implement prefix caching, we do
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nothing.
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"""
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pass
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def mark_blocks_as_computed(self, block_ids: List[int]) -> None:
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"""Mark blocks as computed, used in prefix caching.
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Since the naive allocator does not implement prefix caching, we do
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nothing.
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"""
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pass
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def get_common_computed_block_ids(
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self, seq_block_ids: List[List[int]]) -> List[int]:
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"""Determine blocks that can be skipped in prefill.
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Since the naive allocator does not support prefix caching, always return
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an empty list.
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"""
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return []
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def promote_to_immutable_block(self, block: Block) -> BlockId:
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raise NotImplementedError
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class NaiveBlock(Block):
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"""An implementation of the Block class that does not support prefix
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caching.
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The NaiveBlock class represents a block of token IDs with a fixed size. It
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provides methods for appending token IDs to the block and manages copy-on
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-write operations when necessary.
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Args:
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prev_block (Block): The previous block in the sequence.
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token_ids (List[int]): The initial token IDs to be stored in the block.
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block_size (int): The maximum number of token IDs that can be stored in
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the block.
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allocator (BlockAllocator): The block allocator associated with this
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block.
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block_id (Optional[int], optional): The physical block index
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of this block. Defaults to None, which means no allocation has been
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made.
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_cow_target (Optional[Block], optional): The copy-on-write target block.
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If not provided, it defaults to self.
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"""
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def __init__(self,
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prev_block: Optional[Block],
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token_ids: List[int],
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block_size: int,
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allocator: BlockAllocator,
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block_id: Optional[int] = None,
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_cow_target: Optional[Block] = None):
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self._token_ids: List[int] = []
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self._block_size = block_size
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self._prev_block = prev_block
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self._block_id = block_id
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self._allocator = allocator
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self._cow_target = _cow_target if _cow_target is not None else self
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self._append_token_ids_no_cow(token_ids)
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def append_token_ids(self, token_ids: List[int]) -> None:
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"""Appends the given token IDs to the block, instructing the allocator
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to perform a copy-on-write if necessary.
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Args:
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token_ids (List[int]): The token IDs to be appended to the block.
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"""
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self._append_token_ids_no_cow(token_ids)
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if self._block_id is not None:
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self._block_id = (self._allocator.cow_block_if_not_appendable(
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self._cow_target))
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def _append_token_ids_no_cow(self, token_ids: List[int]) -> None:
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assert self.num_empty_slots >= len(token_ids)
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self._token_ids.extend(token_ids)
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@property
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def computed(self) -> bool:
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raise NotImplementedError
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@computed.setter
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def computed(self, value) -> None:
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raise NotImplementedError
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@property
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def last_accessed(self) -> float:
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raise NotImplementedError
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@last_accessed.setter
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def last_accessed(self, last_accessed_ts: float):
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raise NotImplementedError
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@property
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def block_id(self) -> Optional[int]:
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return self._block_id
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@block_id.setter
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def block_id(self, value: Optional[int]) -> None:
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self._block_id = value
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@property
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def is_full(self) -> bool:
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return self.num_empty_slots == 0
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@property
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def num_empty_slots(self) -> int:
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return self._block_size - len(self._token_ids)
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@property
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def token_ids(self) -> List[int]:
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return self._token_ids
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@property
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def block_size(self) -> int:
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return self._block_size
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@property
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def prev_block(self) -> Optional["Block"]:
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return self._prev_block
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@property
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def content_hash(self) -> Optional[int]:
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return None
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