Skip to main content

/

Docs

Nightly

v24.6

Log in

Mojo struct

ContiguousKVCacheManager

struct ContiguousKVCacheManager[type: DType, kv_params: KVCacheStaticParams]

Manages a Batch-split KV cache across multiple user sessions.

Each request is assigned a seq_id, which is associated with a set of buffers to store the key and value projections per layer.

The order of calls for an active request is expected to be:

  • claim -- assigned blocks to the sequence and give it a unique id
  • step -- commit context encoding projections
  • foreach token generated:
    • fetch -- retrieve blocks based on a seq_id
    • step -- commit token generation projections
  • release -- mark blocks as not in use

TODO this is not currently threadsafe, make it so

Aliases​

  • CollectionType = ContiguousKVCacheCollection[type, kv_params]:

Fields​

  • ​blocks_buf (Tensor[type, 6]):
  • ​num_blocks (Int):
  • ​max_batch_size (Int):
  • ​max_seq_len (Int):
  • ​active_seq_ids (List[Int]):
  • ​cache_lengths (List[Int]):
  • ​seq_id_counter (Int):
  • ​num_layers (Int):
  • ​other_device (Device):
  • ​this_device (Device):
  • ​cache_lengths_tensor_host (DeviceTensor):
  • ​cache_lengths_tensor_dev (DeviceTensor):

Implemented traits​

AnyType, KVCacheManagerT, UnknownDestructibility

Methods​

__init__​

__init__(out self, max_batch_size: Int, max_seq_len: Int, num_layers: Int, mut other_device: Device, mut this_device: Device)

claim​

claim(mut self, batch_size: Int) -> List[Int]

Assign batch_size blocks for incoming requests.

This returns a List of seq_ids, which can be passed to fetch to retrieve the KVCollection for the given batch.

fetch​

fetch[collection_t: KVCollectionT](mut self, seq_ids: List[Int]) -> collection_t

Retrieves the pre-assigned blocks for the given seq_ids.

if any of the seq_ids are not valid (e.g. no assigned blocks) then and error is raised.

step​

step[collection_t: KVCollectionT](mut self, valid_lengths: List[Int], owned inflight_cache: collection_t)

Commits changes to the ContiguousKVCache blocks.

This is used to note that a KV projection step has occured and the values in these buffers have been written to. We note the new tokens in the blocks and update the valid_length counter.

release​

release(mut self, seq_id: Int)

Marks seq_id as no longer necessary, their blocks are reintroduced to the pool.