org.jboss.cache.eviction
Class LFUAlgorithm
java.lang.Object
org.jboss.cache.eviction.BaseEvictionAlgorithm
org.jboss.cache.eviction.BaseSortedEvictionAlgorithm
org.jboss.cache.eviction.LFUAlgorithm
- All Implemented Interfaces:
- EvictionAlgorithm
public class LFUAlgorithm
- extends BaseSortedEvictionAlgorithm
Least Frequently Used algorithm for cache eviction.
Note that this algorithm is not thread-safe.
This algorithm relies on maxNodes and minNodes to operate correctly.
Eviction takes place using Least Frequently Used algorithm. A node A
that is used less than a node B is evicted sooner.
The minNodes property defines a threshold for eviction. If minNodes = 100,
the LFUAlgorithm will not evict the cache to anything less than 100 elements
still left in cache. The maxNodes property defines the maximum number of nodes
the cache will accept before eviction. maxNodes = 0 means that this region is
unbounded. minNodes = 0 means that the eviction queue will attempt to bring
the cache of this region to 0 elements (evict all elements) whenever it is run.
This algorithm uses a sorted eviction queue. The eviction queue is sorted in
ascending order based on the number of times a node is visited. The more frequently
a node is visited, the less likely it will be evicted.
- Version:
- $Revision: 5772 $
- Author:
- Daniel Huang - dhuang@jboss.org 10/2005
Methods inherited from class org.jboss.cache.eviction.BaseEvictionAlgorithm |
emptyRecycleQueue, evict, evictCacheNode, getEvictionQueue, initialize, isNodeInUseAndNotTimedOut, isYoungerThanMinimumTimeToLive, process, processAddedElement, processAddedNodes, processAddedNodes, processMarkInUseNodes, processRemovedElement, processRemovedNodes, processUnmarkInUseNodes, processVisitedNodes, resetEvictionQueue, toString |
LFUAlgorithm
public LFUAlgorithm()
shouldEvictNode
protected boolean shouldEvictNode(NodeEntry ne)
- Description copied from class:
BaseEvictionAlgorithm
- This method will check whether the given node should be evicted or not.
- Specified by:
shouldEvictNode
in class BaseEvictionAlgorithm
- Parameters:
ne
- NodeEntry to test eviction for.
- Returns:
- True if the given node should be evicted. False if the given node should not be evicted.
setupEvictionQueue
protected EvictionQueue setupEvictionQueue(Region region)
throws EvictionException
- Will create a LFUQueue to be used as the underlying eviction queue.
- Specified by:
setupEvictionQueue
in class BaseEvictionAlgorithm
- Parameters:
region
- MarshRegion to create the eviction queue for.
- Returns:
- The created LFUQueue.
- Throws:
EvictionException
- See Also:
EvictionQueue
prune
protected void prune()
throws EvictionException
- Overrides:
prune
in class BaseEvictionAlgorithm
- Throws:
EvictionException
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