ce4f5a29fb
Co-authored-by: ElizaWszola <eliza@neuralmagic.com> Co-authored-by: Michael Goin <michael@neuralmagic.com>
472 lines
19 KiB
Python
472 lines
19 KiB
Python
"""A block manager that manages token blocks."""
|
|
import enum
|
|
from itertools import count
|
|
from os.path import commonprefix
|
|
from typing import Dict, List, Optional, Set, Tuple
|
|
|
|
from vllm.block import BlockTable, PhysicalTokenBlock
|
|
from vllm.sequence import Sequence, SequenceGroup, SequenceStatus
|
|
from vllm.utils import Device
|
|
from vllm.core.evictor import Evictor, EvictionPolicy, make_evictor
|
|
|
|
|
|
class BlockAllocator:
|
|
"""Manages free physical token blocks for a device.
|
|
|
|
The allocator maintains a list of free blocks and allocates a block when
|
|
requested. When a block is freed, its reference count is decremented. If
|
|
the reference count becomes zero, the block is added back to the free list.
|
|
"""
|
|
|
|
def __init__(self,
|
|
device: Device,
|
|
block_size: int,
|
|
num_blocks: int,
|
|
eviction_policy: EvictionPolicy = EvictionPolicy.LRU,
|
|
enable_caching: bool = False) -> None:
|
|
self.device = device
|
|
self.block_size = block_size
|
|
self.num_blocks = num_blocks
|
|
self.enable_caching = enable_caching
|
|
|
|
self.current_num_blocks = 0
|
|
self.cached_blocks: Dict[int, PhysicalTokenBlock] = {}
|
|
|
|
# Switch over to FIFO eviction when caching is disabled
|
|
if not self.enable_caching:
|
|
eviction_policy = EvictionPolicy.FIFO
|
|
self.evictor: Evictor = make_evictor(eviction_policy)
|
|
|
|
self.default_hash_ctr = count()
|
|
|
|
def allocate_block(self, block_hash: int,
|
|
num_hashed_tokens: int) -> PhysicalTokenBlock:
|
|
if self.current_num_blocks == self.num_blocks:
|
|
block = self.evictor.evict()
|
|
block.block_hash = block_hash
|
|
block.num_hashed_tokens = num_hashed_tokens
|
|
return block
|
|
block = PhysicalTokenBlock(device=self.device,
|
|
block_number=self.current_num_blocks,
|
|
block_size=self.block_size,
|
|
block_hash=block_hash,
|
|
num_hashed_tokens=num_hashed_tokens)
|
|
self.current_num_blocks += 1
|
|
return block
|
|
|
|
def allocate(self,
|
|
block_hash: Optional[int] = None,
|
|
num_hashed_tokens: int = 0) -> PhysicalTokenBlock:
|
|
# If caching is disabled, just allocate a new block and return it
|
|
if not self.enable_caching:
|
|
block = self.allocate_block(next(self.default_hash_ctr),
|
|
num_hashed_tokens)
|
|
block.ref_count += 1
|
|
return block
|
|
|
|
if block_hash is None:
|
|
block_hash = next(self.default_hash_ctr)
|
|
if block_hash in self.evictor:
|
|
assert block_hash not in self.cached_blocks
|
|
block = self.evictor.remove(block_hash)
|
|
assert block.ref_count == 0
|
|
self.cached_blocks[block_hash] = block
|
|
block.ref_count += 1
|
|
assert block.block_hash == block_hash
|
|
return block
|
|
if block_hash not in self.cached_blocks:
|
|
self.cached_blocks[block_hash] = self.allocate_block(
|
|
block_hash, num_hashed_tokens)
|
|
block = self.cached_blocks[block_hash]
|
|
assert block.block_hash == block_hash
|
|
block.ref_count += 1
|
|
return block
|
|
|
|
def free(self, block: PhysicalTokenBlock) -> None:
|
|
if block.ref_count == 0:
|
|
raise ValueError(f"Double free! {block} is already freed.")
|
|
block.ref_count -= 1
|
|
if block.ref_count == 0:
|
|
assert block.block_hash not in self.evictor
|
|
self.evictor.add(block)
|
|
|
|
# If caching is enabled, remove the block from the cached_blocks
|
|
if self.enable_caching:
|
|
del self.cached_blocks[block.block_hash]
|
|
|
|
def get_num_free_blocks(self) -> int:
|
|
return self.num_blocks - self.current_num_blocks + self.evictor.num_blocks
|
|
|
|
def contains_block(self, block_hash: int) -> bool:
|
|
return block_hash in self.cached_blocks or block_hash in self.evictor
|
|
|
|
def update_hash(self, block_hash: int, block: PhysicalTokenBlock):
|
|
# If caching is enabled, update the hash of block and the cached_blocks dictionary.
|
|
if self.enable_caching:
|
|
assert not self.contains_block(block_hash)
|
|
old_hash = block.block_hash
|
|
block.block_hash = block_hash
|
|
del self.cached_blocks[old_hash]
|
|
self.cached_blocks[block_hash] = block
|
|
|
|
|
|
class AllocStatus(enum.Enum):
|
|
"""Result for BlockSpaceManager.can_allocate
|
|
|
|
1. Ok: seq_group can be allocated now.
|
|
2. Later: seq_group cannot be allocated.
|
|
The capacity of allocator is larger than seq_group required.
|
|
3. Never: seq_group can never be allocated.
|
|
The seq_group is too large to allocated in GPU.
|
|
"""
|
|
OK = enum.auto()
|
|
LATER = enum.auto()
|
|
NEVER = enum.auto()
|
|
|
|
|
|
class BlockSpaceManager:
|
|
"""Manages the mapping between logical and physical token blocks."""
|
|
|
|
def __init__(
|
|
self,
|
|
block_size: int,
|
|
num_gpu_blocks: int,
|
|
num_cpu_blocks: int,
|
|
watermark: float = 0.01,
|
|
sliding_window: Optional[int] = None,
|
|
enable_caching: bool = False,
|
|
) -> None:
|
|
self.block_size = block_size
|
|
self.num_total_gpu_blocks = num_gpu_blocks
|
|
self.num_total_cpu_blocks = num_cpu_blocks
|
|
|
|
self.block_sliding_window = None
|
|
if sliding_window is not None:
|
|
assert sliding_window % block_size == 0, (sliding_window,
|
|
block_size)
|
|
self.block_sliding_window = sliding_window // block_size
|
|
|
|
self.watermark = watermark
|
|
assert watermark >= 0.0
|
|
|
|
self.enable_caching = enable_caching
|
|
|
|
self.watermark_blocks = int(watermark * num_gpu_blocks)
|
|
self.gpu_allocator = BlockAllocator(Device.GPU,
|
|
block_size,
|
|
num_gpu_blocks,
|
|
enable_caching=enable_caching)
|
|
self.cpu_allocator = BlockAllocator(Device.CPU,
|
|
block_size,
|
|
num_cpu_blocks,
|
|
enable_caching=enable_caching)
|
|
# Mapping: seq_id -> BlockTable.
|
|
self.block_tables: Dict[int, BlockTable] = {}
|
|
|
|
def can_allocate(self, seq_group: SequenceGroup) -> AllocStatus:
|
|
# FIXME(woosuk): Here we assume that all sequences in the group share
|
|
# the same prompt. This may not be true for preempted sequences.
|
|
seq = seq_group.get_seqs(status=SequenceStatus.WAITING)[0]
|
|
num_required_blocks = len(seq.logical_token_blocks)
|
|
|
|
if self.block_sliding_window is not None:
|
|
num_required_blocks = min(num_required_blocks,
|
|
self.block_sliding_window)
|
|
num_free_gpu_blocks = self.gpu_allocator.get_num_free_blocks()
|
|
|
|
# Use watermark to avoid frequent cache eviction.
|
|
if (self.num_total_gpu_blocks - num_required_blocks <
|
|
self.watermark_blocks):
|
|
return AllocStatus.NEVER
|
|
if num_free_gpu_blocks - num_required_blocks >= self.watermark_blocks:
|
|
return AllocStatus.OK
|
|
else:
|
|
return AllocStatus.LATER
|
|
|
|
def allocate(self, seq_group: SequenceGroup) -> None:
|
|
# NOTE: Here we assume that all sequences in the group have the same
|
|
# prompt.
|
|
seq = seq_group.get_seqs(status=SequenceStatus.WAITING)[0]
|
|
|
|
# Allocate new physical token blocks that will store the prompt tokens.
|
|
num_prompt_blocks = len(seq.logical_token_blocks)
|
|
|
|
block_table: BlockTable = []
|
|
for logical_idx in range(num_prompt_blocks):
|
|
if (self.block_sliding_window is not None
|
|
and logical_idx >= self.block_sliding_window):
|
|
block = block_table[logical_idx % self.block_sliding_window]
|
|
else:
|
|
block = self.gpu_allocator.allocate(
|
|
seq.hash_of_block(logical_idx),
|
|
seq.num_hashed_tokens_of_block(logical_idx))
|
|
block_table.append(block)
|
|
|
|
# Assign the block table for each sequence.
|
|
for seq in seq_group.get_seqs(status=SequenceStatus.WAITING):
|
|
self.block_tables[seq.seq_id] = block_table.copy()
|
|
|
|
def can_append_slot(self, seq_group: SequenceGroup) -> bool:
|
|
# Simple heuristic: If there is at least one free block
|
|
# for each sequence, we can append.
|
|
num_free_gpu_blocks = self.gpu_allocator.get_num_free_blocks()
|
|
num_seqs = seq_group.num_seqs(status=SequenceStatus.RUNNING)
|
|
return num_seqs <= num_free_gpu_blocks
|
|
|
|
def _promote_last_block(
|
|
self,
|
|
seq: Sequence,
|
|
last_block: PhysicalTokenBlock,
|
|
) -> PhysicalTokenBlock:
|
|
# Compute a new hash for the block so that it can be shared by other Sequences
|
|
new_hash = seq.hash_of_block(len(seq.logical_token_blocks) - 1)
|
|
|
|
# if new_hash is already in the cached table, then free last_block and return the cached version
|
|
if self.gpu_allocator.contains_block(new_hash):
|
|
self.gpu_allocator.free(last_block)
|
|
return self.gpu_allocator.allocate(new_hash)
|
|
else:
|
|
self.gpu_allocator.update_hash(new_hash, last_block)
|
|
return last_block
|
|
|
|
def _is_last_block_full(
|
|
self,
|
|
seq: Sequence,
|
|
) -> bool:
|
|
token_ids_len = len(seq.data.get_token_ids())
|
|
return token_ids_len > 0 and token_ids_len % seq.block_size == 0
|
|
|
|
def _is_last_block(
|
|
self,
|
|
seq: Sequence,
|
|
index: int,
|
|
) -> bool:
|
|
return index == len(seq.logical_token_blocks) - 1
|
|
|
|
def _maybe_promote_last_block(
|
|
self,
|
|
seq: Sequence,
|
|
last_block: PhysicalTokenBlock,
|
|
) -> PhysicalTokenBlock:
|
|
if self._is_last_block_full(seq):
|
|
return self._promote_last_block(seq, last_block)
|
|
else:
|
|
return last_block
|
|
|
|
def _allocate_last_physical_block(
|
|
self,
|
|
seq: Sequence,
|
|
) -> PhysicalTokenBlock:
|
|
block_hash: Optional[int] = None
|
|
if (self._is_last_block_full(seq)):
|
|
block_hash = seq.hash_of_block(len(seq.logical_token_blocks) - 1)
|
|
num_hashed_tokens = seq.num_hashed_tokens_of_block(
|
|
len(seq.logical_token_blocks) - 1)
|
|
new_block = self.gpu_allocator.allocate(block_hash, num_hashed_tokens)
|
|
if block_hash is None:
|
|
assert new_block.ref_count == 1
|
|
return new_block
|
|
|
|
def append_slot(
|
|
self,
|
|
seq: Sequence,
|
|
) -> Optional[Tuple[int, int]]:
|
|
"""Allocate a physical slot for a new token."""
|
|
logical_blocks = seq.logical_token_blocks
|
|
block_table = self.block_tables[seq.seq_id]
|
|
# If we need to allocate a new physical block
|
|
if len(block_table) < len(logical_blocks):
|
|
# Currently this code only supports adding one physical block
|
|
assert len(block_table) == len(logical_blocks) - 1
|
|
|
|
if (self.block_sliding_window
|
|
and len(block_table) >= self.block_sliding_window):
|
|
# reuse a block
|
|
block_table.append(block_table[len(block_table) %
|
|
self.block_sliding_window])
|
|
else:
|
|
# The sequence has a new logical block.
|
|
# Allocate a new physical block.
|
|
new_block = self._allocate_last_physical_block(seq)
|
|
block_table.append(new_block)
|
|
return None
|
|
|
|
# We want to append the token to the last physical block.
|
|
last_block = block_table[-1]
|
|
assert last_block.device == Device.GPU
|
|
if last_block.ref_count == 1:
|
|
# Not shared with other sequences. Appendable.
|
|
# If the last block is now complete, promote it to a full block so that it can be shared
|
|
new_block = self._maybe_promote_last_block(seq, last_block)
|
|
block_table[-1] = new_block
|
|
return None
|
|
else:
|
|
# The last block is shared with other sequences.
|
|
# Copy on Write: Allocate a new block and copy the tokens.
|
|
new_block = self._allocate_last_physical_block(seq)
|
|
|
|
block_table[-1] = new_block
|
|
self.gpu_allocator.free(last_block)
|
|
return last_block.block_number, new_block.block_number
|
|
|
|
def fork(self, parent_seq: Sequence, child_seq: Sequence) -> None:
|
|
# NOTE: fork does not allocate a new physical block.
|
|
# Thus, it is always safe from OOM.
|
|
src_block_table = self.block_tables[parent_seq.seq_id]
|
|
self.block_tables[child_seq.seq_id] = src_block_table.copy()
|
|
for block in src_block_table:
|
|
block.ref_count += 1
|
|
|
|
def _get_physical_blocks(
|
|
self, seq_group: SequenceGroup) -> List[PhysicalTokenBlock]:
|
|
# NOTE: Here, we assume that the physical blocks are only shared by
|
|
# the sequences in the same group.
|
|
blocks: Set[PhysicalTokenBlock] = set()
|
|
for seq in seq_group.get_seqs():
|
|
if seq.is_finished():
|
|
continue
|
|
blocks.update(self.block_tables[seq.seq_id])
|
|
return list(blocks)
|
|
|
|
def can_swap_in(self, seq_group: SequenceGroup) -> bool:
|
|
blocks = self._get_physical_blocks(seq_group)
|
|
num_swapped_seqs = seq_group.num_seqs(status=SequenceStatus.SWAPPED)
|
|
num_free_blocks = self.gpu_allocator.get_num_free_blocks()
|
|
# NOTE: Conservatively, we assume that every sequence will allocate
|
|
# at least one free block right after the swap-in.
|
|
# NOTE: This should match the logic in can_append_slot().
|
|
num_required_blocks = len(blocks) + num_swapped_seqs
|
|
return num_free_blocks - num_required_blocks >= self.watermark_blocks
|
|
|
|
def swap_in(self, seq_group: SequenceGroup) -> Dict[int, int]:
|
|
# CPU block -> GPU block.
|
|
mapping: Dict[PhysicalTokenBlock, PhysicalTokenBlock] = {}
|
|
for seq in seq_group.get_seqs(status=SequenceStatus.SWAPPED):
|
|
new_block_table: BlockTable = []
|
|
block_table = self.block_tables[seq.seq_id]
|
|
|
|
for cpu_block in block_table:
|
|
if cpu_block in mapping:
|
|
gpu_block = mapping[cpu_block]
|
|
gpu_block.ref_count += 1
|
|
else:
|
|
gpu_block = self.gpu_allocator.allocate(
|
|
cpu_block.block_hash, cpu_block.num_hashed_tokens)
|
|
mapping[cpu_block] = gpu_block
|
|
new_block_table.append(gpu_block)
|
|
# Free the CPU block swapped in to GPU.
|
|
self.cpu_allocator.free(cpu_block)
|
|
self.block_tables[seq.seq_id] = new_block_table
|
|
|
|
block_number_mapping = {
|
|
cpu_block.block_number: gpu_block.block_number
|
|
for cpu_block, gpu_block in mapping.items()
|
|
}
|
|
return block_number_mapping
|
|
|
|
def can_swap_out(self, seq_group: SequenceGroup) -> bool:
|
|
blocks = self._get_physical_blocks(seq_group)
|
|
return len(blocks) <= self.cpu_allocator.get_num_free_blocks()
|
|
|
|
def swap_out(self, seq_group: SequenceGroup) -> Dict[int, int]:
|
|
# GPU block -> CPU block.
|
|
mapping: Dict[PhysicalTokenBlock, PhysicalTokenBlock] = {}
|
|
for seq in seq_group.get_seqs(status=SequenceStatus.RUNNING):
|
|
new_block_table: BlockTable = []
|
|
block_table = self.block_tables[seq.seq_id]
|
|
|
|
for gpu_block in block_table:
|
|
if gpu_block in mapping:
|
|
cpu_block = mapping[gpu_block]
|
|
cpu_block.ref_count += 1
|
|
else:
|
|
cpu_block = self.cpu_allocator.allocate(
|
|
gpu_block.block_hash, gpu_block.num_hashed_tokens)
|
|
mapping[gpu_block] = cpu_block
|
|
new_block_table.append(cpu_block)
|
|
# Free the GPU block swapped out to CPU.
|
|
self.gpu_allocator.free(gpu_block)
|
|
self.block_tables[seq.seq_id] = new_block_table
|
|
|
|
block_number_mapping = {
|
|
gpu_block.block_number: cpu_block.block_number
|
|
for gpu_block, cpu_block in mapping.items()
|
|
}
|
|
return block_number_mapping
|
|
|
|
def _free_block_table(self, block_table: BlockTable) -> None:
|
|
for block in set(block_table):
|
|
if block.device == Device.GPU:
|
|
self.gpu_allocator.free(block)
|
|
else:
|
|
self.cpu_allocator.free(block)
|
|
|
|
def free(self, seq: Sequence) -> None:
|
|
if seq.seq_id not in self.block_tables:
|
|
# Already freed or haven't been scheduled yet.
|
|
return
|
|
block_table = self.block_tables[seq.seq_id]
|
|
self._free_block_table(block_table)
|
|
del self.block_tables[seq.seq_id]
|
|
|
|
def reset(self) -> None:
|
|
for block_table in self.block_tables.values():
|
|
self._free_block_table(block_table)
|
|
self.block_tables.clear()
|
|
|
|
def get_block_table(self, seq: Sequence) -> List[int]:
|
|
block_table = self.block_tables[seq.seq_id]
|
|
return [block.block_number for block in block_table]
|
|
|
|
def get_num_free_gpu_blocks(self) -> int:
|
|
return self.gpu_allocator.get_num_free_blocks()
|
|
|
|
def get_num_free_cpu_blocks(self) -> int:
|
|
return self.cpu_allocator.get_num_free_blocks()
|
|
|
|
def access_all_blocks_in_seq(
|
|
self,
|
|
seq: Sequence,
|
|
access_time: float,
|
|
) -> None:
|
|
block_table = self.block_tables[seq.seq_id]
|
|
for block in block_table:
|
|
block.last_accessed = access_time
|
|
|
|
def compute_last_full_block_in_seq(self, seq: Sequence):
|
|
if seq.seq_id not in self.block_tables:
|
|
return
|
|
max_full_block = seq.get_len() // seq.block_size - 1
|
|
block_table = self.block_tables[seq.seq_id]
|
|
if max_full_block == -1:
|
|
return
|
|
block_table[max_full_block].computed = True
|
|
|
|
def get_all_block_ids_till_computed(self, seq: Sequence) -> List[int]:
|
|
if seq.seq_id not in self.block_tables:
|
|
return []
|
|
block_table = self.block_tables[seq.seq_id]
|
|
for block_idx in reversed(range(len(block_table))):
|
|
if block_table[block_idx].computed:
|
|
return [b.block_number for b in block_table[:block_idx + 1]]
|
|
return []
|
|
|
|
# Can return non-empty result only with prefix caching enabled.
|
|
def get_common_computed_block_ids(self,
|
|
seq_group: SequenceGroup) -> List[int]:
|
|
if not self.enable_caching:
|
|
return []
|
|
|
|
ids_list = [
|
|
self.get_all_block_ids_till_computed(seq)
|
|
for seq in iter(seq_group.seqs_dict.values())
|
|
]
|
|
return commonprefix([ids for ids in ids_list if ids != []])
|
|
|
|
# We only mark the last full block because with prefix caching,
|
|
# all blocks until the marked one are guaranteed to be computed.
|
|
def mark_blocks_as_computed(self, seq_group: SequenceGroup):
|
|
if self.enable_caching:
|
|
for seq in seq_group.seqs_dict.values():
|
|
self.compute_last_full_block_in_seq(seq)
|