init

v1/core/kv_cache_utils.py

@@ -0,0 +1,996 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""KV-Cache Utilities."""
+
+import os
+from collections import defaultdict, deque
+from collections.abc import Iterable, Sequence
+from dataclasses import dataclass
+from typing import Any, Callable, NamedTuple, Optional
+
+from vllm.config import VllmConfig
+from vllm.logger import init_logger
+from vllm.utils import GiB_bytes, cdiv, sha256
+from vllm.v1.kv_cache_interface import (FullAttentionSpec, KVCacheConfig,
+                                        KVCacheGroupSpec, KVCacheSpec,
+                                        KVCacheTensor, SlidingWindowSpec)
+from vllm.v1.metrics.stats import PrefixCacheStats
+from vllm.v1.request import Request
+
+logger = init_logger(__name__)
+
+
+class BlockHash(NamedTuple):
+    """Hash value of a block (int), the token IDs in the block, and extra keys.
+    We keep a tuple of token IDs and extra keys to reduce the likelihood of
+    hash collisions when the hash value is the same. By using SHA256 however,
+    hash collisions are practically impossible.
+    """
+    # Hash value of the block in an integer.
+    hash_value: int
+    # Token IDs in the block.
+    token_ids: tuple[int, ...]
+    # Extra keys for the block.
+    extra_keys: Optional[Any] = None
+
+
+class BlockHashWithGroupId(NamedTuple):
+    # The hash value for the contents (e.g., token_ids) of a block without group
+    # ID. The value is the same for blocks representing the same tokens but for
+    # different groups.
+    block_hash: BlockHash
+    # The KV cache group ID.
+    group_id: int
+
+    def get_hash_value(self) -> int:
+        return self.block_hash.hash_value
+
+
+# The hash seed for the first block of the prefix block sequence.
+#
+# Even if the hash function is the builtin hash(), we use sha256 to generate
+# the initial hash to simplify the code. This is not performance critical
+# as it is done one per process.
+#
+# We use a random value to avoid hash collisions or PYTHONHASHSEED environment
+# variable if set such that processes can share the seed if needed.
+# This aligns with the behavior of Python's hash() function, which also uses
+# a random seed if PYTHONHASHSEED is not set.
+NONE_HASH = int.from_bytes(os.urandom(32), byteorder="big") if os.getenv(
+    "PYTHONHASHSEED") is None else sha256(os.getenv("PYTHONHASHSEED"))
+
+
+class PrefixCachingMetrics:
+    """Metrics for prefix caching with a hit rate of the max recent N requests.
+
+    Args:
+        max_recent_requests: The number of the max recent requests to aggregate.
+            Defaults to 1000.
+    """
+
+    def __init__(self, max_recent_requests: int = 1000):
+        self.max_recent_requests = max_recent_requests
+        # The current aggregated values.
+        self.aggregated_requests = 0
+        self.aggregated_query_total = 0
+        self.aggregated_query_hit = 0
+        # A deque of (requests, queries, hits) for the most recent requests.
+        self.query_queue: deque[tuple[int, int, int]] = deque()
+
+    def observe(self, stats: PrefixCacheStats):
+        """Observe the prefix caching for a set of requests.
+
+        This function is called with information gathered when new requests
+        are being scheduled and are looking for computed blocks.
+
+        When there are more than `interval` requests, the oldest set of
+        requests are removed from the metrics.
+
+        Args:
+            stats: The prefix cache stats.
+        """
+        # reset_prefix_cache was invoked before the current update.
+        # Reset the metrics before aggregating the current stats.
+        if stats.reset:
+            self.reset()
+
+        # Update the metrics.
+        self.query_queue.append((stats.requests, stats.queries, stats.hits))
+        self.aggregated_requests += stats.requests
+        self.aggregated_query_total += stats.queries
+        self.aggregated_query_hit += stats.hits
+
+        # Remove the oldest stats if the number of requests exceeds.
+        if self.aggregated_requests > self.max_recent_requests:
+            old_requests, old_queries, old_hits = self.query_queue.popleft()
+            self.aggregated_requests -= old_requests
+            self.aggregated_query_total -= old_queries
+            self.aggregated_query_hit -= old_hits
+
+    def reset(self):
+        """Reset the metrics."""
+        self.aggregated_requests = 0
+        self.aggregated_query_total = 0
+        self.aggregated_query_hit = 0
+        self.query_queue.clear()
+
+    @property
+    def hit_rate(self) -> float:
+        """Calculate the hit rate for the past N requests."""
+        if self.aggregated_query_total == 0:
+            return 0.0
+        return self.aggregated_query_hit / self.aggregated_query_total
+
+
+@dataclass
+class KVCacheBlock:
+    """KV-cache block metadata."""
+    # Block ID, ranging from 0 to num_gpu_blocks - 1.
+    block_id: int
+    # Reference count.
+    ref_cnt: int = 0
+    # The hash of the block composed of (block hash, tuple of token IDs).
+    # It is only available when the block is full.
+    _block_hash: Optional[BlockHashWithGroupId] = None
+
+    # Used to construct a doubly linked list for free blocks.
+    # These two attributes should only be manipulated by FreeKVCacheBlockQueue.
+    prev_free_block: Optional["KVCacheBlock"] = None
+    next_free_block: Optional["KVCacheBlock"] = None
+
+    # Whether the block is a null block that should never be cached.
+    is_null: bool = False
+
+    def incr_ref(self):
+        self.ref_cnt += 1
+
+    def decr_ref(self):
+        self.ref_cnt -= 1
+
+    @property
+    def block_hash(self) -> Optional[BlockHashWithGroupId]:
+        return self._block_hash
+
+    @block_hash.setter
+    def block_hash(self, block_hash: BlockHashWithGroupId):
+        assert self.block_hash is None, (
+            "The block already has a hash. This should not happen.")
+        self._block_hash = block_hash
+
+    def reset_hash(self):
+        """Reset the block hash when the block is evicted."""
+        self._block_hash = None
+
+    def __repr__(self) -> str:
+        # Use block_id instead of KVCacheBlock object to avoid calling __repr__
+        # on KVCacheBlock object recursively.
+        prev_block_id = (self.prev_free_block.block_id
+                         if self.prev_free_block else None)
+        next_block_id = (self.next_free_block.block_id
+                         if self.next_free_block else None)
+        return (f"KVCacheBlock(block_id={self.block_id}, "
+                f"ref_cnt={self.ref_cnt}, "
+                f"_block_hash={self._block_hash}, "
+                f"prev_free_block={prev_block_id}, "
+                f"next_free_block={next_block_id})")
+
+
+class FreeKVCacheBlockQueue:
+    """This class organizes a list of KVCacheBlock objects to a doubly linked
+    list of free blocks. We implement this class instead of using Python
+    builtin deque to support removing a block in the middle of the queue
+    in O(1) time. To close the performance gap to the builtin deque which is
+    implemented in C++, this class does not allocate any Python objects when
+    manipulating the linked list. Instead, this class manipulates the
+    prev_free_block and next_free_block attributes of the given blocks.
+
+    The queue is ordered by block ID in the beginning. When a block is allocated
+    and then freed, it will be appended back with the eviction order:
+    1. The least recent used block is at the front (LRU).
+    2. If two blocks have the same last accessed time (allocated by the
+       same sequence), the one with more hash tokens (the tail of a block
+       chain) is at the front.
+    Note that we maintain this order by reversing the block order when free
+    blocks of a request. This operation is outside of this class.
+
+    Args:
+        blocks: A list of KVCacheBlock objects.
+    """
+
+    def __init__(self, blocks: list[KVCacheBlock]) -> None:
+        self.num_free_blocks = len(blocks)
+
+        # Initialize the doubly linked list of free blocks.
+        self.free_list_head: Optional[KVCacheBlock] = blocks[0]
+        self.free_list_tail: Optional[KVCacheBlock] = blocks[-1]
+        for i in range(self.num_free_blocks):
+            if i > 0:
+                blocks[i].prev_free_block = blocks[i - 1]
+            if i < self.num_free_blocks - 1:
+                blocks[i].next_free_block = blocks[i + 1]
+
+    def popleft(self) -> KVCacheBlock:
+        """Pop the first free block and reduce num_free_blocks by 1.
+
+        Returns:
+            The first free block.
+        """
+        if not self.free_list_head:
+            raise ValueError("No free blocks available")
+
+        block = self.free_list_head
+        self.remove(block)
+        return block
+
+    def remove(self, block: KVCacheBlock) -> None:
+        """Remove a block in the free list and reduce num_free_blocks by 1.
+
+        Args:
+            block: The block to remove.
+        """
+        if block.prev_free_block is not None:
+            # Link the previous block to the next block.
+            block.prev_free_block.next_free_block = block.next_free_block
+        if block.next_free_block is not None:
+            # Link the next block to the previous block.
+            block.next_free_block.prev_free_block = block.prev_free_block
+
+        if block == self.free_list_head:
+            # Update the head if the block is the head.
+            self.free_list_head = block.next_free_block
+        if block == self.free_list_tail:
+            # Update the tail if the block is the tail.
+            self.free_list_tail = block.prev_free_block
+
+        # Remove the block from the linked list.
+        block.prev_free_block = block.next_free_block = None
+        self.num_free_blocks -= 1
+
+    def append(self, block: KVCacheBlock) -> None:
+        """Put a block back into the free list and increase
+        num_free_blocks by 1.
+
+        Args:
+            block: The block to append.
+        """
+        if self.free_list_tail is not None:
+            # Link the last block to the new block.
+            self.free_list_tail.next_free_block = block
+            block.prev_free_block = self.free_list_tail
+            self.free_list_tail = block
+        else:
+            # The free list is empty.
+            assert self.free_list_head is None
+            self.free_list_head = self.free_list_tail = block
+
+        block.next_free_block = None
+        self.num_free_blocks += 1
+
+    def get_all_free_blocks(self) -> list[KVCacheBlock]:
+        """Get all free blocks in the free list. Mainly used for testing.
+
+        Returns:
+            A list of free blocks.
+        """
+        ret = []
+        curr_block = self.free_list_head
+        while curr_block is not None:
+            ret.append(curr_block)
+            curr_block = curr_block.next_free_block
+        return ret
+
+
+def need_extra_keys(request: Request) -> bool:
+    """Check whether the blocks allocated to this request need extra hash keys.
+
+    Args:
+        request (Request): The request.
+
+    Returns:
+        bool: Whether blocks allocated to this request need extra hash keys.
+    """
+
+    # Multimodal requests need to include the MM hash.
+    # LoRA requests need to include the LoRA ID.
+    # Request with provided cache salt need to include the salt.
+    return bool(request.mm_positions) or (request.lora_request
+                                          is not None) or (request.cache_salt
+                                                           is not None)
+
+
+def _gen_mm_extra_hash_keys(request: Request, start_token_idx: int,
+                            end_token_idx: int,
+                            start_mm_idx: int) -> tuple[list[Any], int]:
+    """Generate extra keys related to MultiModal request for block hash
+    computation. For multi-modal inputs, the extra keys are
+    (mm_hash, start_offset) that indicate a mm input contained in the
+    block and its starting offset in the block tokens.
+
+    Args:
+        request: The request object.
+        start_token_idx: The start token index of the block.
+        end_token_idx: The end token index of the block.
+        start_mm_idx: The start multi-modal index of the block.
+
+    Returns:
+        A tuple of extra keys and the next multi-modal index.
+    """
+    extra_keys: list[Any] = []
+
+    mm_positions, mm_hashes = request.mm_positions, request.mm_hashes
+    if not mm_positions:
+        return extra_keys, start_mm_idx
+
+    if mm_positions and len(mm_positions) != len(mm_hashes):
+        raise ValueError(
+            "The number of multi-modal positions and hashes must match. This "
+            "is likely because you do not enable MM preprocessor hashing. "
+            "Please set disable_mm_preprocessor_cache=False.")
+
+    # Note that we assume mm_positions is sorted by offset.
+    # We do not need to check all mm inputs if the start token index is out of
+    # range. This usually happens in the late prefill phase and decoding phase.
+    if mm_positions[-1].offset + mm_positions[-1].length < start_token_idx:
+        return extra_keys, start_mm_idx
+
+    # Support start_mm_idx == -1 to indicate the last mm input.
+    if start_mm_idx < 0:
+        assert -start_mm_idx <= len(mm_positions)
+        start_mm_idx = len(mm_positions) + start_mm_idx
+
+    curr_mm_idx = start_mm_idx
+    while mm_positions and curr_mm_idx < len(mm_positions):
+        assert mm_hashes[curr_mm_idx] is not None
+        offset = mm_positions[curr_mm_idx].offset
+        length = mm_positions[curr_mm_idx].length
+        if end_token_idx > offset:
+            if start_token_idx > offset + length:
+                # This block has passed the current mm input.
+                curr_mm_idx += 1
+                continue
+
+            # The block contains the current mm input.
+            extra_keys.append(mm_hashes[curr_mm_idx])
+
+            if end_token_idx >= offset + length:
+                # If this block contains the end of the current mm input,
+                # move to the next mm input as this block may also contain
+                # the next mm input.
+                curr_mm_idx += 1
+            else:
+                # Otherwise this block is done with mm inputs.
+                break
+        else:
+            # This block has not reached the current mm input.
+            break
+    return extra_keys, curr_mm_idx
+
+
+def _gen_lora_extra_hash_keys(request: Request) -> list[int]:
+    """Generate extra keys related to LoRA for block hash computation.
+
+    Args:
+        request: The request object.
+
+    Returns:
+        Return LoRA id of the request if it is a LoRA request. Return empty
+        list otherwise.
+    """
+    if not request.lora_request:
+        return []
+    return [request.lora_request.lora_int_id]
+
+
+def generate_block_hash_extra_keys(
+        request: Request, start_token_idx: int, end_token_idx: int,
+        start_mm_idx: int) -> tuple[Optional[tuple[Any, ...]], int]:
+    """Generate extra keys for the block hash. The extra keys can come from
+    the multi-modal inputs and request specific metadata (e.g., LoRA ID).
+
+    Args:
+        request: The request object.
+        start_token_idx: The start token index of the block.
+        end_token_idx: The end token index of the block.
+        start_mm_idx: The start multi-modal index of the block.
+
+    Returns:
+        A tuple of extra keys and the next multi-modal index.
+    """
+    mm_extra_keys: list[Any]
+    mm_extra_keys, new_start_mm_idx = _gen_mm_extra_hash_keys(
+        request, start_token_idx, end_token_idx, start_mm_idx)
+    lora_extra_keys: list[int] = _gen_lora_extra_hash_keys(request)
+    cache_salt_keys: list[str] = [request.cache_salt] if (
+        start_token_idx == 0 and request.cache_salt) else []
+
+    extra_keys: list[Any] = lora_extra_keys + mm_extra_keys + cache_salt_keys
+
+    if not extra_keys:
+        return None, new_start_mm_idx
+
+    return tuple(extra_keys), new_start_mm_idx
+
+
+def hash_block_tokens(
+        hash_function: Callable,
+        parent_block_hash: Optional[int],
+        curr_block_token_ids: Sequence[int],
+        extra_keys: Optional[tuple[Any, ...]] = None) -> BlockHash:
+    """Computes a hash value corresponding to the contents of a block and
+    the contents of the preceding block(s). The hash value is used for
+    prefix caching. We use LRU cache for this function to avoid recomputing
+    hash values for the same block contents.
+
+    Args:
+        parent_block_hash: The hash of the parent block. None
+            if this is the first block.
+        curr_block_token_ids: A list of token ids in the current
+            block. The current block is assumed to be full.
+        extra_keys: Extra keys for the block.
+
+    Returns:
+        The hash value of the block and the token ids in the block.
+        The entire tuple is used as the hash key of the block.
+    """
+    if not parent_block_hash:
+        parent_block_hash = NONE_HASH
+
+    curr_block_token_ids_tuple = tuple(curr_block_token_ids)
+    return BlockHash(
+        hash_function(
+            (parent_block_hash, curr_block_token_ids_tuple, extra_keys)),
+        curr_block_token_ids_tuple, extra_keys)
+
+
+def hash_request_tokens(hash_function: Any, block_size: int,
+                        request: Request) -> list[BlockHash]:
+    """Computes hash values of a chain of blocks given a sequence of
+    token IDs. The hash value is used for prefix caching.
+
+    Args:
+        block_size: The size of each block.
+        request: The request object.
+
+    Returns:
+        The list of computed hash values.
+    """
+    token_ids = request.all_token_ids
+
+    req_need_extra_keys = need_extra_keys(request)
+    req_extra_keys = None
+    curr_mm_idx = 0
+
+    ret = []
+    parent_block_hash_value = None
+    for start in range(0, len(token_ids), block_size):
+        end = start + block_size
+        block_token_ids = token_ids[start:end]
+        # Do not hash the block if it is not full.
+        if len(block_token_ids) < block_size:
+            break
+
+        if req_need_extra_keys:
+            # MM and LoRA requests need extra keys for block-hash computation.
+            req_extra_keys, curr_mm_idx = generate_block_hash_extra_keys(
+                request, start, end, curr_mm_idx)
+
+        block_hash = hash_block_tokens(hash_function, parent_block_hash_value,
+                                       block_token_ids, req_extra_keys)
+        ret.append(block_hash)
+        parent_block_hash_value = block_hash.hash_value
+    return ret
+
+
+def max_memory_usage_bytes(vllm_config: VllmConfig,
+                           kv_cache_specs: Iterable[KVCacheSpec]) -> int:
+    """
+    Get the maximum memory usage in bytes for the given KV cache specs.
+    """
+    return sum(
+        spec.max_memory_usage_bytes(vllm_config) for spec in kv_cache_specs)
+
+
+def estimate_max_model_len(vllm_config: VllmConfig,
+                           kv_cache_spec: dict[str, KVCacheSpec],
+                           available_memory: int) -> int:
+    """
+    Estimates the maximum model length that can fit in the available memory
+    using binary search.
+
+    Args:
+        vllm_config: The global VllmConfig
+        kv_cache_spec: The kv cache spec of each attention layer in the model
+        available_memory: Memory available for KV cache in bytes.
+
+    Returns:
+        The estimated maximum model length that can fit in the available memory.
+    """
+
+    # Define a function to check if a given model length fits in memory
+    def fits_in_memory(model_len: int) -> bool:
+        # Modify the max_model_len for this calculation
+        vllm_config.model_config.max_model_len = model_len
+        # Calculate memory needed for the given model length
+        memory_needed = max_memory_usage_bytes(vllm_config,
+                                               kv_cache_spec.values())
+        return memory_needed <= available_memory
+
+    # Binary search for the maximum model length
+    current_max = vllm_config.model_config.max_model_len
+    left, right = 1, current_max
+
+    # If even the smallest model length doesn't fit, return 0
+    if not fits_in_memory(left):
+        return 0
+
+    # Binary search for the maximum model length that fits
+    result = 1
+    while left <= right:
+        mid = (left + right) // 2
+        if fits_in_memory(mid):
+            result = mid
+            left = mid + 1
+        else:
+            right = mid - 1
+    return result
+
+
+def check_enough_kv_cache_memory(vllm_config: VllmConfig,
+                                 kv_cache_spec: dict[str, KVCacheSpec],
+                                 available_memory: int):
+    """
+    Checks whether `available_memory` is enough for the KV cache to hold at
+    least one request with the model's max_model_len.
+
+    Args:
+        vllm_config: The global VllmConfig
+        kv_cache_spec: The kv cache spec of each attention layer in the model
+        available_memory: Memory available for KV cache in bytes.
+
+    Raises:
+        ValueError: If there is not enough memory available for the KV cache.
+    """
+
+    if available_memory <= 0:
+        raise ValueError("No available memory for the cache blocks. "
+                         "Try increasing `gpu_memory_utilization` when "
+                         "initializing the engine.")
+
+    max_model_len = vllm_config.model_config.max_model_len
+    needed_memory = max_memory_usage_bytes(vllm_config, kv_cache_spec.values())
+
+    if needed_memory > available_memory:
+        # Estimate the maximum model length that can fit in the available memory
+        estimated_max_len = estimate_max_model_len(vllm_config, kv_cache_spec,
+                                                   available_memory)
+        estimated_msg = ""
+        if estimated_max_len > 0:
+            estimated_msg = (
+                "Based on the available memory, "
+                f"the estimated maximum model length is {estimated_max_len}.")
+
+        raise ValueError(
+            f"To serve at least one request with the models's max seq len "
+            f"({max_model_len}), ({needed_memory/GiB_bytes:.2f} GiB KV "
+            f"cache is needed, which is larger than the available KV cache "
+            f"memory ({available_memory/GiB_bytes:.2f} GiB). "
+            f"{estimated_msg} "
+            f"Try increasing `gpu_memory_utilization` or decreasing "
+            f"`max_model_len` when initializing the engine.")
+
+
+def create_kv_cache_group_specs(
+        kv_cache_spec: dict[str, KVCacheSpec],
+        grouped_layer_names: list[list[str]]) -> list[KVCacheGroupSpec]:
+    """
+    Create KVCacheGroupSpec object for each kv cache group layer.
+    The layers in the same group should share the same
+    KVCacheSpec.
+
+    Args:
+        kv_cache_spec:
+            A mapping from each layer name to its corresponding KVCacheSpec.
+        grouped_layer_names:
+            A list of kv cache groups, where each element is a list of layer
+            names that belong to the same group and should share the same
+            KVCacheSpec.
+    Returns:
+        A list of KVCacheGroupSpec objects, one for each group.
+    """
+    kv_cache_groups = []
+    for layer_names_one_group in grouped_layer_names:
+        layer_specs = [
+            kv_cache_spec[layer_name] for layer_name in layer_names_one_group
+        ]
+        merged_layer_spec = layer_specs[0].merge(layer_specs)
+        kv_cache_groups.append(
+            KVCacheGroupSpec(layer_names_one_group, merged_layer_spec))
+    return kv_cache_groups
+
+
+def is_kv_cache_type_uniform(kv_cache_spec: dict[str, KVCacheSpec]) -> bool:
+    """
+    Whether all layers in the given KVCacheSpec have the same type of KV cache.
+
+    Args:
+        kv_cache_spec: The kv cache spec of each attention layer in the model
+
+    Returns:
+        True if all layers have the same type, False otherwise.
+    """
+
+    layer_keys = set(layer.type_id for layer in kv_cache_spec.values())
+    return len(layer_keys) == 1
+
+
+def get_max_concurrency_for_kv_cache_config(
+        vllm_config: VllmConfig, kv_cache_config: KVCacheConfig) -> float:
+    """
+    Get the maximum concurrency for the given KV cache configuration.
+    """
+    num_layer_per_group = max(
+        len(group.layer_names) for group in kv_cache_config.kv_cache_groups)
+    max_memory_usage_per_request = num_layer_per_group * max_memory_usage_bytes(
+        vllm_config,
+        (group.kv_cache_spec for group in kv_cache_config.kv_cache_groups))
+    memory_per_block = kv_cache_config.kv_cache_groups[
+        0].kv_cache_spec.page_size_bytes * num_layer_per_group
+    num_block_per_request = cdiv(max_memory_usage_per_request,
+                                 memory_per_block)
+    max_concurrency = kv_cache_config.num_blocks / num_block_per_request
+    return max_concurrency
+
+
+def get_num_blocks(vllm_config: VllmConfig, num_layers: int,
+                   available_memory: int, page_size: int) -> int:
+    """
+    Get the number of kv cache blocks.
+
+    Args:
+        vllm_config: The global VllmConfig
+        num_layers: The number of layers
+        available_memory: Memory available for KV cache in bytes.
+        page_size: The page size of the KV cache.
+    """
+    num_blocks = int(available_memory // page_size // num_layers)
+    num_blocks = max(num_blocks, 0)
+    if vllm_config.cache_config.num_gpu_blocks_override is not None:
+        num_gpu_blocks_override = \
+            vllm_config.cache_config.num_gpu_blocks_override
+        logger.info(
+            "Overriding num_gpu_blocks=%d with "
+            "num_gpu_blocks_override=%d", num_blocks, num_gpu_blocks_override)
+    return num_blocks
+
+
+def get_uniform_page_size(kv_cache_spec: dict[str, KVCacheSpec]) -> int:
+    """
+    Get the page size of the KV cache.
+    """
+    page_sizes = set(layer.page_size_bytes for layer in kv_cache_spec.values())
+    assert len(page_sizes) == 1
+    return page_sizes.pop()
+
+
+def _get_kv_cache_config_uniform_type(vllm_config: VllmConfig,
+                                      kv_cache_spec: dict[str, KVCacheSpec],
+                                      available_memory: int) -> KVCacheConfig:
+    """
+    Generates the KV cache configuration for a model with one type of KV cache.
+    Divide the available memory equally among all layers.
+
+    Args:
+        vllm_config: The global VllmConfig
+        kv_cache_spec: The kv cache spec of each attention layer in the model
+        available_memory: Memory available for KV cache in bytes.
+
+    Returns:
+        The generated KVCacheConfig
+    """
+
+    page_size = get_uniform_page_size(kv_cache_spec)
+    num_blocks = get_num_blocks(vllm_config, len(kv_cache_spec),
+                                available_memory, page_size)
+
+    per_layer_size = page_size * num_blocks
+    # All layers have the same KV cache spec, so we create one kv cache group
+    # for all layers.
+    grouped_layer_names = [list(kv_cache_spec.keys())]
+
+    # Each layer uses a separate Tensor to store its KV cache.
+    kv_cache_tensors = [
+        KVCacheTensor(size=per_layer_size, shared_by=[layer_name])
+        for layer_name in kv_cache_spec
+    ]
+
+    kv_cache_config = KVCacheConfig(
+        num_blocks=num_blocks,
+        kv_cache_tensors=kv_cache_tensors,
+        kv_cache_groups=create_kv_cache_group_specs(kv_cache_spec,
+                                                    grouped_layer_names),
+    )
+
+    num_tokens = num_blocks * vllm_config.cache_config.block_size
+    num_tokens_str = f"{num_tokens:,}"
+    logger.info("GPU KV cache size: %s tokens", num_tokens_str)
+    max_model_len_str = f"{vllm_config.model_config.max_model_len:,}"
+    max_concurrency = get_max_concurrency_for_kv_cache_config(
+        vllm_config, kv_cache_config)
+    logger.info("Maximum concurrency for %s tokens per request: %.2fx",
+                max_model_len_str, max_concurrency)
+    return kv_cache_config
+
+
+def is_kv_cache_page_size_uniform(
+        kv_cache_spec: dict[str, KVCacheSpec]) -> bool:
+    """
+    Whether all layers in the given KVCacheSpec have the same page size.
+    Args:
+        kv_cache_spec: The KVCacheSpec of each attention layer in the model
+
+    Returns:
+        True if all layers have the same page size, False otherwise.
+    """
+
+    page_sizes = {layer.page_size_bytes for layer in kv_cache_spec.values()}
+    return len(page_sizes) == 1
+
+
+def _get_kv_cache_config_uniform_page_size(
+        vllm_config: VllmConfig, kv_cache_spec: dict[str, KVCacheSpec],
+        available_memory: int) -> KVCacheConfig:
+    """
+    Generates the KV cache configuration for hybrid models with multiple 
+    attention types but still with a uniform page size (physical memory per 
+    block per layer) for all layers.
+
+    Detailed explanation about kv cache management of hybrid models:
+    The layers in the models are repeated with some patterns, e.g., a model
+    with 10 full attention layers and 20 sliding window attention layers can be
+    regarded as repeating the pattern (1 * full, 2 * sw) 10 times. 
+    The KVCacheManager allocates different block tables for each of the 3 layers
+    in the pattern, and repeats each of them 10 times to generate the 
+    block_table for the 30 layers in the model.
+    Therefore, we can group the layers in the model into 3 kv_cache_groups, each
+    of which contains 10 layers in the model.
+    The KVCacheManager allocates the block_table for each group based on its
+    kv_cache spec, and the model runner applies the block table to each layer 
+    in the group.
+    For example:
+    1. A model only uses full attention. The pattern is 
+    (num_hidden_layers * full), so there is only one group and the block table 
+    is shared by all layers. It is already handled by 
+    `_get_kv_cache_config_uniform_type`.
+    2. A model with 10 full attention layers and 20 sliding window 
+    attention layers. There are 3 layers in the pattern (1 * full, 2 * sw), so 
+    there are 3 kv_cache_groups, each of which represents 10 layers.
+
+    To simplify the implementation, we make the following assumptions:
+    1. Physical memory per block: Must be the same across all KV cache groups. 
+    Breaking this assumption is non-trivial due to memory fragmentation concerns
+    when allocating blocks of different sizes.
+    2. Tokens per block (block_size): Currently, we directly use 
+    `CacheConfig.block_size` for all layers. It can be extended to vary by KV 
+    cache group, but within each KV cache group, all layers must share the same 
+    block size.
+    3. Physical memory per token per layer: This property is decided by model 
+    config. Currently we only support models that have the same physical memory 
+    per token per layer for all layers. Can be relaxed with a simple extension, 
+    but still need to keep physical memory per block the same for all groups.
+    4. Number of layers per group: Currently assumed the same for all layers. 
+    Can be relaxed with a simple extension, but still need to keep physical 
+    memory per block the same for all groups.
+    5. Attention type within groups: All layers in a group must share the same
+    attention type. One exception is that, when 
+    `--disable-hybrid-kv-cache-manager` is true, the single group for full 
+    attention layers may also include attention layers using sliding window or 
+    LLaMA 4 local attention. See `unify_hybrid_kv_cache_specs` for more details.
+    6. Support for multiple attention types: The design for most components is 
+    general to an arbitrary number of attention types. But 
+    `find_longest_cache_hit` only supports one attention type or two 
+    types of full-attention plus exactly one another type. The general
+    implementation of this function is feasible but we don't know how to 
+    implement it cleanly yet.
+
+    As we assume tokens per block, physical memory per token per layer, and 
+    number of layers per group are the same now, we can ensure that physical 
+    memory per block is the same for all groups.
+
+    Args:
+        vllm_config: The global VllmConfig
+        kv_cache_spec: The KVCacheSpec of each attention layer in the model
+        available_memory: Memory available for KV cache in bytes.
+    Returns:
+        The generated KVCacheConfig
+    """
+    # Group all layers by type_id.
+    # E.g., 2 full attention layers and 3 sliding window attention layers,
+    # -> (full.0, full.1), (sw.0, sw.1, sw.2).
+    same_type_layers: dict[str, list[str]] = defaultdict(list)
+    for layer_name, layer_spec in kv_cache_spec.items():
+        same_type_layers[layer_spec.type_id].append(layer_name)
+
+    # Split each group into smaller groups, to make the number of layers in each
+    # group identical. Add padding to the last group of each type if necessary.
+    # E.g., (full.0, full.1), (sw.0, sw.1, sw.2)
+    # split to 3 groups with 2 layers each:
+    # (full.0, full.1), (sw.0, sw.1), (sw.2, padding).
+    # FIXME(Chen): At the moment of writing this code (2025-06-02), all
+    # open-source hybrid model follows a n:1 pattern between different attention
+    # types (e.g., Gemma3 5:1 between sw and full, LLaMA4 3:1 between local and
+    # full), so we can use the "1" in the n:1 pattern as the group size, which
+    # is the minimum number of layers among all attention types. Need a better
+    # strategy if we want to support more complex patterns (e.g., 20 full + 30
+    # sw, where the group size should be 10).
+    group_size = min([len(layers) for layers in same_type_layers.values()])
+    grouped_layers = []
+    for layers in same_type_layers.values():
+        num_padding_layers = group_size - len(layers) % group_size
+        if num_padding_layers != group_size:
+            logger.warning(
+                "Add %d padding layers, may waste at most %.2f%% KV cache memory",  # noqa
+                num_padding_layers,
+                num_padding_layers / len(layers) * 100,
+            )
+        for i in range(0, len(layers), group_size):
+            grouped_layers.append(layers[i:i + group_size])
+    kv_cache_groups = create_kv_cache_group_specs(kv_cache_spec,
+                                                  grouped_layers)
+
+    # Determine how model runners should initialize the KV cache tensors.
+    # We will have group_size memory pools, each is shared by one layer from
+    # each group. As layers of different groups have different block table,
+    # they will use different parts of the shared Tensor.
+    # The memory layout in the example will be:
+    # full.0, sw.0, sw.2: share a Tensor with size=available_memory//2
+    # full.1, sw.1: share another Tensor with size=available_memory//2
+    page_size = get_uniform_page_size(kv_cache_spec)
+    num_blocks = get_num_blocks(vllm_config, group_size, available_memory,
+                                page_size)
+    per_memory_pool_size = page_size * num_blocks
+    kv_cache_tensors = []
+    for i in range(group_size):
+        shared_by = []
+        for j in range(len(kv_cache_groups)):
+            if i < len(grouped_layers[j]):
+                shared_by.append(grouped_layers[j][i])
+        kv_cache_tensors.append(
+            KVCacheTensor(size=per_memory_pool_size, shared_by=shared_by))
+
+    kv_cache_config = KVCacheConfig(
+        num_blocks=num_blocks,
+        kv_cache_tensors=kv_cache_tensors,
+        kv_cache_groups=kv_cache_groups,
+    )
+
+    # Print the KV cache size and maximum concurrency.
+    num_tokens = num_blocks // len(
+        grouped_layers) * vllm_config.cache_config.block_size
+    num_tokens_str = f"{num_tokens:,}"
+    logger.info("GPU KV cache size: %s tokens", num_tokens_str)
+    max_model_len_str = f"{vllm_config.model_config.max_model_len:,}"
+    max_concurrency = get_max_concurrency_for_kv_cache_config(
+        vllm_config, kv_cache_config)
+    logger.info("Maximum concurrency for %s tokens per request: %.2fx",
+                max_model_len_str, max_concurrency)
+    return kv_cache_config
+
+
+def unify_hybrid_kv_cache_specs(kv_cache_spec: dict[str, KVCacheSpec]):
+    """
+    This function tries to convert the KV cache specs to one type if the model
+    is a hybrid model with multiple type of KV cache. It will convert all
+    SlidingWindowSpec to FullAttentionSpec if both types are present.
+
+    Args:
+        kv_cache_spec: The kv cache spec of each attention layer in the model
+    """
+
+    def is_hybrid(kv_cache_spec: dict[str, KVCacheSpec]) -> bool:
+        type_ids = set(layer_spec.type_id
+                       for layer_spec in kv_cache_spec.values())
+        return len(type_ids) > 1
+
+    if not is_hybrid(kv_cache_spec):
+        return
+
+    logger.warning(
+        "Hybrid KV cache manager is disabled for this hybrid model, "
+        "This means we do not enable any optimizations for saving KV cache "
+        "memory (e.g., dropping the KV cache outside the sliding window). "
+        "The compute of layers like sliding window is still saved.")
+
+    has_full_attention = any(
+        isinstance(spec, FullAttentionSpec) for spec in kv_cache_spec.values())
+    has_sliding_window = any(
+        isinstance(spec, SlidingWindowSpec) for spec in kv_cache_spec.values())
+    if has_full_attention and has_sliding_window:
+        for layer_name, spec in kv_cache_spec.items():
+            if isinstance(spec, SlidingWindowSpec):
+                kv_cache_spec[layer_name] = FullAttentionSpec(
+                    block_size=spec.block_size,
+                    num_kv_heads=spec.num_kv_heads,
+                    head_size=spec.head_size,
+                    dtype=spec.dtype,
+                    use_mla=spec.use_mla,
+                    sliding_window=spec.sliding_window,
+                )
+
+    if is_hybrid(kv_cache_spec):
+        raise ValueError("Hybrid KV cache manager is disabled but failed to "
+                         "convert the KV cache specs to one unified type.")
+
+
+def get_kv_cache_config(
+    vllm_config: VllmConfig,
+    kv_cache_spec: dict[str, KVCacheSpec],
+    available_memory: int,
+) -> KVCacheConfig:
+    """
+    Generates the KV cache configuration for a model.
+
+    Args:
+        vllm_config: The global VllmConfig
+        kv_cache_spec: The kv cache spec of each attention layer in the model
+        available_memory: Memory available for KV cache in bytes.
+
+    Returns:
+        The generated KVCacheConfigs
+    """
+    check_enough_kv_cache_memory(vllm_config, kv_cache_spec, available_memory)
+
+    if vllm_config.scheduler_config.disable_hybrid_kv_cache_manager:
+        unify_hybrid_kv_cache_specs(kv_cache_spec)
+
+    if is_kv_cache_type_uniform(kv_cache_spec):
+        # KV cache of all layers are the same, which is true for
+        # most models. Allocate the same amount of memory for
+        # each layer.
+        return _get_kv_cache_config_uniform_type(vllm_config, kv_cache_spec,
+                                                 available_memory)
+    elif is_kv_cache_page_size_uniform(kv_cache_spec):
+        # Model contains multiple attention types, but KV cache of all layers
+        # have the same physical memory per block per layer. Split the layers
+        # into groups with the same number of layers, and thus same total page
+        # size.
+        return _get_kv_cache_config_uniform_page_size(vllm_config,
+                                                      kv_cache_spec,
+                                                      available_memory)
+
+    raise NotImplementedError
+
+
+def unify_kv_cache_configs(kv_cache_configs: list[KVCacheConfig]):
+    """
+    Make the KV cache configurations for each worker consistent, so that all
+    workers can be controlled by the same KVCacheManager.
+    This function verifies that the layer group of each worker are the same,
+    and changes the num_blocks of each worker to the smallest among all workers.
+
+    Args:
+        kv_cache_configs: The KV cache configurations for each worker. Will be
+            in-place modified to make them consistent.
+    """
+
+    # Sort the kv cache groups by the type_id of their KV cache spec.
+    # This can avoid the inconsistency caused by the order of groups.
+    for kv_cache_config in kv_cache_configs:
+        kv_cache_config.kv_cache_groups.sort(
+            key=lambda x: x.kv_cache_spec.type_id)
+
+    # Verify that the groups of each rank are the same.
+    for kv_cache_config in kv_cache_configs[1:]:
+        for group_rank_0, group_rank_i in zip(
+                kv_cache_configs[0].kv_cache_groups,
+                kv_cache_config.kv_cache_groups):
+            assert group_rank_0.kv_cache_spec == group_rank_i.kv_cache_spec
+
+    # Change the num_blocks of each rank to the smallest among all ranks. We
+    # do not need to shrink the tensor size because it is valid to only use the
+    # first `num_blocks` blocks of the tensor.
+    min_num_blocks = min(kv_cache_config.num_blocks
+                         for kv_cache_config in kv_cache_configs)
+    for kv_cache_config in kv_cache_configs:
+        kv_cache_config.num_blocks = min_num_blocks
+
+    return kv_cache_configs