sglang/python/sglang/srt/mem_cache/base_prefix_cache.py

from __future__ import annotations

import dataclasses
import time
from abc import ABC, abstractmethod
from typing import (
    TYPE_CHECKING,
    Any,
    NamedTuple,
    Optional,
    Protocol,
    Tuple,
    runtime_checkable,
)

import torch

from sglang.srt.mem_cache.allocator import BaseTokenToKVPoolAllocator
from sglang.srt.mem_cache.memory_pool import ReqToTokenPool
from sglang.srt.metrics.collector import RadixCacheMetricsCollector

if TYPE_CHECKING:
    from sglang.srt.managers.schedule_batch import Req
    from sglang.srt.mem_cache.radix_cache import RadixKey


@runtime_checkable
class PrefixCacheTrait(Protocol):
    req_to_token_pool: ReqToTokenPool
    token_to_kv_pool_allocator: BaseTokenToKVPoolAllocator
    page_size: int
    disable: bool


@dataclasses.dataclass
class MatchPrefixParams:
    """Unified parameters for match_prefix across different cache types"""

    key: RadixKey

    # Mamba specific
    cow_mamba: bool = False
    req: Optional[Req] = None


@dataclasses.dataclass
class InsertParams:
    """Unified parameters for insert across different cache types"""

    key: RadixKey
    value: Optional[torch.Tensor] = None

    # Mamba specific
    mamba_value: Optional[torch.Tensor] = None

    # SWA specific
    prev_prefix_len: int = 0
    swa_evicted_seqlen: int = 0

    # General
    chunked: bool = False
    priority: int = 0


@dataclasses.dataclass
class InsertResult:
    """Result of an insert operation"""

    prefix_len: int
    mamba_exist: bool = False


@dataclasses.dataclass
class EvictParams:
    """Unified parameters for evict across different cache types"""

    num_tokens: int
    swa_num_tokens: int = 0
    mamba_num: int = 0


@dataclasses.dataclass
class EvictResult:
    """Result of an evict operation"""

    num_tokens_evicted: int = 0
    swa_num_tokens_evicted: int = 0
    mamba_num_evicted: int = 0


class MatchResult(NamedTuple):
    """Result of a prefix match operation.

    Attributes:
        device_indices  :   Indices of the KV cache on the device matched by common prefix.
        last_device_node:   The last TreeNode on the device that was matched.
        last_host_node  :   The last TreeNode on the host that was matched.
                            Note that if HiCache is not enabled,
                            this **must** be the same as `last_device_node`.
        host_hit_length :   Length of the KV cache hit on the host, if applicable.
                            0 if HiCache is not enabled.
        mamba_branching_seqlen: The mamba radix cache branching point, which is the longest
                                page-aligned position that could've been cache hit if there
                                exists a mamba state.
    """

    device_indices: torch.Tensor
    last_device_node: Any
    last_host_node: Any
    host_hit_length: int = 0
    mamba_branching_seqlen: Optional[int] = None


class BasePrefixCache(ABC, PrefixCacheTrait):
    """Cache can be indexed by either rid or key."""

    metrics_collector: Optional[RadixCacheMetricsCollector] = (
        None  # metrics collector for the cache
    )

    def init_metrics_collector(self):
        self.metrics_collector = RadixCacheMetricsCollector(
            labels={"cache_type": self.__class__.__name__}
        )

    def update_eviction_metrics(self, num_evicted: int, start_time: float):
        if self.metrics_collector is not None and num_evicted > 0:
            self.metrics_collector.observe_eviction_duration(
                time.perf_counter() - start_time
            )
            self.metrics_collector.increment_eviction_num_tokens(num_evicted)

    @abstractmethod
    def reset(self):
        pass

    @abstractmethod
    def match_prefix(self, params: MatchPrefixParams) -> MatchResult:
        pass

    @abstractmethod
    def cache_finished_req(self, req: Req, is_insert: bool = True, **kwargs):
        pass

    @abstractmethod
    def cache_unfinished_req(self, req: Req, **kwargs):
        pass

    @abstractmethod
    def evict(self, params: EvictParams) -> EvictResult:
        pass

    @abstractmethod
    def inc_lock_ref(self, node: Any):
        pass

    @abstractmethod
    def dec_lock_ref(self, node: Any, swa_uuid_for_lock: Optional[str] = None):
        pass

    def evictable_size(self):
        return 0

    def full_evictable_size(self):
        return 0

    def swa_evictable_size(self):
        return 0

    def protected_size(self):
        return 0

    def full_protected_size(self):
        return 0

    def swa_protected_size(self):
        return 0

    def total_size(self):
        raise NotImplementedError()

    def pretty_print(self):
        raise NotImplementedError()

    def init_load_back(
        self,
        last_host_node: Any,
        host_hit_length: int,
    ) -> Tuple[torch.Tensor, Any]:
        """
        Preparing KV cache loading from host to device.
        """
        raise NotImplementedError()

    def ready_to_load_host_cache(self) -> Any:
        """
        Notify the cache controller to start the KV cache loading
        """
        raise NotImplementedError()

    def check_hicache_events(self) -> Any:
        """
        Check HiCache related activities to update radix tree and synchronize across TP workers if needed
        """
        raise NotImplementedError()

    def take_events(self):
        return []

    def supports_swa(self) -> bool:
        return False

    def supports_mamba(self) -> bool:
        return False

    def is_chunk_cache(self) -> bool:
        return False

    def is_tree_cache(self) -> bool:
        return not self.is_chunk_cache()