[feat] Added chunked prefill and kvcache offload mechenism.

nanovllm/kvcache/policies/__init__.py

@@ -0,0 +1,51 @@
+"""
+Eviction policy plugins for KV cache offloading.
+
+Users can create custom policies by subclassing EvictionPolicy
+and specifying the full class path in config.offload_policy.
+"""
+
+from nanovllm.kvcache.policies.base_policy import EvictionPolicy
+from nanovllm.kvcache.policies.lru_policy import LRUPolicy
+from nanovllm.kvcache.policies.fifo_policy import FIFOPolicy
+
+# Built-in policy registry
+BUILTIN_POLICIES = {
+    "lru": LRUPolicy,
+    "fifo": FIFOPolicy,
+}
+
+
+def get_policy(policy_name: str) -> EvictionPolicy:
+    """
+    Get an eviction policy instance by name or class path.
+
+    Args:
+        policy_name: Either a built-in name ("lru", "fifo") or
+                    a full class path ("mymodule.MyPolicy")
+
+    Returns:
+        EvictionPolicy instance
+    """
+    # Check built-in policies first
+    if policy_name.lower() in BUILTIN_POLICIES:
+        return BUILTIN_POLICIES[policy_name.lower()]()
+
+    # Try to import custom policy
+    try:
+        module_path, class_name = policy_name.rsplit(".", 1)
+        import importlib
+        module = importlib.import_module(module_path)
+        policy_class = getattr(module, class_name)
+        if not issubclass(policy_class, EvictionPolicy):
+            raise TypeError(f"{policy_name} is not a subclass of EvictionPolicy")
+        return policy_class()
+    except (ValueError, ImportError, AttributeError) as e:
+        raise ValueError(
+            f"Unknown policy '{policy_name}'. "
+            f"Available built-in policies: {list(BUILTIN_POLICIES.keys())}. "
+            f"For custom policies, use full class path: 'mymodule.MyPolicy'"
+        ) from e
+
+
+__all__ = ["EvictionPolicy", "LRUPolicy", "FIFOPolicy", "get_policy", "BUILTIN_POLICIES"]