K - the key typeV - the value typepublic class CacheLIRS<K,V>
extends java.util.AbstractMap<K,V>
This implementation is multi-threading safe and supports concurrent access. Null keys or null values are not allowed. The map fill factor is at most 75%.
Each entry is assigned a distinct memory size, and the cache will try to use at most the specified amount of memory. The memory unit is not relevant, however it is suggested to use bytes as the unit.
This class implements an approximation of the the LIRS replacement algorithm invented by Xiaodong Zhang and Song Jiang as described in http://www.cse.ohio-state.edu/~zhang/lirs-sigmetrics-02.html with a few smaller changes: An additional queue for non-resident entries is used, to prevent unbound memory usage. The maximum size of this queue is at most the size of the rest of the stack. About 6.25% of the mapped entries are cold.
Internally, the cache is split into a number of segments, and each segment is an individual LIRS cache.
Accessed entries are only moved to the top of the stack if at least a number of other entries have been moved to the front (8 per segment by default). Write access and moving entries to the top of the stack is synchronized per segment.
| Constructor and Description |
|---|
CacheLIRS(long maxMemory)
Create a new cache with the given number of entries, and the default
settings (16 segments, and stack move distance of 8.
|
CacheLIRS(long maxMemory,
int segmentCount,
int stackMoveDistance)
Create a new cache with the given memory size.
|
| Modifier and Type | Method and Description |
|---|---|
void |
clear()
Remove all entries.
|
boolean |
containsKey(java.lang.Object key)
Check whether there is a resident entry for the given key.
|
java.util.Set<java.util.Map.Entry<K,V>> |
entrySet()
Get the entry set for all resident entries.
|
V |
get(java.lang.Object key)
Get the value for the given key if the entry is cached.
|
long |
getMaxMemory()
Get the maximum memory to use.
|
int |
getMemory(K key)
Get the memory used for the given key.
|
long |
getUsedMemory()
Get the currently used memory.
|
java.util.List<K> |
keys(boolean cold,
boolean nonResident)
Get the list of keys.
|
java.util.Set<K> |
keySet()
Get the set of keys for resident entries.
|
protected void |
onRemove(K key)
This method is called after the value for the given key was removed.
|
V |
peek(K key)
Get the value for the given key if the entry is cached.
|
V |
put(K key,
V value)
Add an entry to the cache using a memory size of 1.
|
V |
put(K key,
V value,
int memory)
Add an entry to the cache.
|
V |
remove(java.lang.Object key)
Remove an entry.
|
void |
setMaxMemory(long maxMemory)
Set the maximum memory this cache should use.
|
int |
size()
Get the number of resident entries.
|
int |
sizeHot()
Get the number of hot entries in the cache.
|
int |
sizeMapArray()
Get the length of the internal map array.
|
int |
sizeNonResident()
Get the number of non-resident entries in the cache.
|
protected int |
sizeOf(K key,
V value)
Get the size of the given value.
|
clone, containsValue, equals, hashCode, isEmpty, putAll, toString, valuespublic CacheLIRS(long maxMemory)
maxMemory - the maximum memory to use (1 or larger)public CacheLIRS(long maxMemory,
int segmentCount,
int stackMoveDistance)
maxMemory - the maximum memory to use (1 or larger)segmentCount - the number of cache segments (must be a power of 2)stackMoveDistance - how many other item are to be moved to the top
of the stack before the current item is movedpublic void clear()
public boolean containsKey(java.lang.Object key)
public V peek(K key)
key - the key (may not be null)public V put(K key, V value, int memory)
key - the key (may not be null)value - the value (may not be null)memory - the memory used for the given entryprotected int sizeOf(K key, V value)
key - the keyvalue - the valueprotected void onRemove(K key)
key - the keypublic V remove(java.lang.Object key)
public int getMemory(K key)
key - the key (may not be null)public V get(java.lang.Object key)
public long getUsedMemory()
public void setMaxMemory(long maxMemory)
maxMemory - the maximum size (1 or larger)public long getMaxMemory()
public java.util.Set<java.util.Map.Entry<K,V>> entrySet()
public java.util.Set<K> keySet()
public int sizeNonResident()
public int sizeMapArray()
public int sizeHot()
public int size()
public java.util.List<K> keys(boolean cold, boolean nonResident)
cold - if true, only keys for the cold entries are returnednonResident - true for non-resident entries