Move the KV cache

The move interface is defined as the following:

move(old_position: Tuple[str, str], new_position: Tuple[str, str],
     tokens: Optional[List[int]] = [], copy: Optional[bool] = False) -> event_id: str, num_tokens: int

The function moves the KV cache chunks identified by tokens from old_position to new_position. Each position is a tuple of (instance_id, location). Setting copy to True copies the KV cache instead of moving it.

Example usage:

First, prepare two yaml files instance1.yaml and instance2.yaml to configure two lmcache instances:

# instance1.yaml
chunk_size: 256
local_cpu: True
max_local_cpu_size: 5

enable_controller: True
lmcache_instance_id: "lmcache_instance_1"
controller_url: "localhost:9001"
lmcache_worker_port: 8002
distributed_url: "localhost:8004"

# instance2.yaml
chunk_size: 256
local_cpu: True
max_local_cpu_size: 5

enable_controller: True
lmcache_instance_id: "lmcache_instance_2"
controller_url: "localhost:9001"
lmcache_worker_port: 8003
distributed_url: "localhost:8005"

Start two vllm engines:

CUDA_VISIBLE_DEVICES=0 LMCACHE_CONFIG_FILE=instance1.yaml vllm serve meta-llama/Llama-3.1-8B-Instruct --max-model-len 4096 \
  --gpu-memory-utilization 0.8 --port 8000 --kv-transfer-config '{"kv_connector":"LMCacheConnectorV1", "kv_role":"kv_both"}'

CUDA_VISIBLE_DEVICES=1 LMCACHE_CONFIG_FILE=instance2.yaml vllm serve meta-llama/Llama-3.1-8B-Instruct --max-model-len 4096 \
  --gpu-memory-utilization 0.8 --port 8001 --kv-transfer-config '{"kv_connector":"LMCacheConnectorV1", "kv_role":"kv_both"}'

Start the lmcache controller at port 9000 and the monitor at port 9001:

lmcache_controller --host localhost --port 9000 --monitor-port 9001

Send a request to vllm engine 1:

curl -X POST http://localhost:8000/v1/completions \
  -H "Content-Type: application/json" \
  -d '{
        "model": "meta-llama/Llama-3.1-8B-Instruct",
        "prompt": "Explain the significance of KV cache in language models.",
        "max_tokens": 10
      }'

Tokenize the prompt to obtain token ids:

curl -X POST http://localhost:8000/tokenize \
  -H "Content-Type: application/json" \
  -d '{
        "model": "meta-llama/Llama-3.1-8B-Instruct",
        "prompt": "Explain the significance of KV cache in language models."
      }'

Move the KV cache from engine 1’s CPU to engine 2’s CPU using the token ids:

curl -X POST http://localhost:9000/move \
  -H "Content-Type: application/json" \
  -d '{
        "old_position": ["lmcache_instance_1", "LocalCPUBackend"],
        "new_position": ["lmcache_instance_2", "LocalCPUBackend"],
        "tokens": [128000, 849, 21435, 279, 26431, 315, 85748, 6636, 304, 4221, 4211, 13]
      }'

The controller responds with a message similar to:

{"num_tokens": 12, "event_id": "xxx"}

num_tokens indicates how many tokens’ KV cache are being moved. The returned event_id can be used to query the status of the operation.