Source code for lmcache.experimental.storage_backend.evictor.lru_evictor

from collections import OrderedDict
from typing import List, Tuple, Union

from lmcache.experimental.storage_backend.evictor.base_evictor import (
    BaseEvictor, PutStatus)
from lmcache.logging import init_logger
from lmcache.utils import CacheEngineKey

logger = init_logger(__name__)




class LRUEvictor(BaseEvictor):
    """
    LRU cache evictor
    """

    def __init__(self, max_cache_size: float = 10.0):
        # The storage size limit (in bytes)
        self.MAX_CACHE_SIZE = int(max_cache_size * 1024**3)

        # TODO(Jiayi): need a way to avoid fragmentation
        # current storage size (in bytes)
        self.current_cache_size = 0.0



    def update_on_hit(self, key: Union[CacheEngineKey, str],
                      cache_dict: OrderedDict) -> None:
        cache_dict.move_to_end(key)




    def update_on_put(
            self, cache_dict: OrderedDict,
            cache_size: int) -> Tuple[List[CacheEngineKey], PutStatus]:
        evict_keys = []
        iter_cache_dict = iter(cache_dict)

        if cache_size > self.MAX_CACHE_SIZE:
            logger.warning("Put failed due to limited cache storage")
            return [], PutStatus.ILLEGAL

        # evict cache until there's enough space
        while cache_size + self.current_cache_size > \
            self.MAX_CACHE_SIZE:
            evict_key = next(iter_cache_dict)
            evict_cache_size = cache_dict[evict_key].size
            self.current_cache_size -= evict_cache_size
            evict_keys.append(evict_key)

        # update cache size
        self.current_cache_size += cache_size
        if len(evict_keys) > 0:
            logger.debug(
                f"Evicting {len(evict_keys)} chunks, "
                f"Current cache size: {self.current_cache_size} bytes, "
                f"Max cache size: {self.MAX_CACHE_SIZE} bytes")
        return evict_keys, PutStatus.LEGAL


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