Package io.debezium.util

Class BoundedConcurrentHashMap.LIRS<K,V>

java.lang.Object

io.debezium.util.BoundedConcurrentHashMap.LIRS<K,V>

All Implemented Interfaces:

BoundedConcurrentHashMap.EvictionPolicy<K,V>

Enclosing class:

BoundedConcurrentHashMap<K,V>

static final class BoundedConcurrentHashMap.LIRS<K,V>
extends Object
implements BoundedConcurrentHashMap.EvictionPolicy<K,V>

Field Summary

Fields

Modifier and Type	Field	Description
private final ConcurrentLinkedQueue<BoundedConcurrentHashMap.LIRSHashEntry<K,V>>	accessQueue	The accessQueue for reducing lock contention See "BP-Wrapper: a system framework making any replacement algorithms (almost) lock contention free"
private final float	batchThresholdFactor
private final BoundedConcurrentHashMap.LIRSHashEntry<K,V>	header	This header encompasses two data structures:
private int	hotSize	The actual number of hot entries.
private static final float	L_LIRS	The percentage of the cache which is dedicated to hot blocks.
private final int	maxBatchQueueSize	The maxBatchQueueSize
private final int	maximumHotSize	The maximum number of hot entries (L_lirs in the paper).
private final int	maximumSize	The maximum number of resident entries (L in the paper).
private final BoundedConcurrentHashMap.Segment<K,V>	segment	The owning segment
private int	size	The number of LIRS entries in a segment

Fields inherited from interface io.debezium.util.BoundedConcurrentHashMap.EvictionPolicy

MAX_BATCH_SIZE

Constructor Summary

Constructors

Constructor	Description
LIRS(BoundedConcurrentHashMap.Segment<K,V> s, int capacity, int maxBatchSize, float batchThresholdFactor)

Method Summary

Modifier and Type	Method	Description
private static int	calculateLIRSize(int maximumSize)
void	clear()	Invoked to notify EvictionPolicy implementation that all Segment entries have been cleared.
BoundedConcurrentHashMap.HashEntry<K,V>	createNewEntry(K key, int hash, BoundedConcurrentHashMap.HashEntry<K,V> next, V value)
Set<BoundedConcurrentHashMap.HashEntry<K,V>>	execute()	Invokes eviction policy algorithm and returns set of evicted entries.
boolean	onEntryHit(BoundedConcurrentHashMap.HashEntry<K,V> e)	Invoked to notify EvictionPolicy implementation that an entry in Segment has been accessed.
Set<BoundedConcurrentHashMap.HashEntry<K,V>>	onEntryMiss(BoundedConcurrentHashMap.HashEntry<K,V> en)	Invoked to notify EvictionPolicy implementation that there has been an attempt to access an entry in Segment, however that entry was not present in Segment.
void	onEntryRemove(BoundedConcurrentHashMap.HashEntry<K,V> e)	Invoked to notify EvictionPolicy implementation that an entry e has been removed from Segment.
private void	pruneStack(Set<BoundedConcurrentHashMap.HashEntry<K,V>> evicted)	Prunes HIR blocks in the bottom of the stack until an HOT block sits in the stack bottom.
private BoundedConcurrentHashMap.LIRSHashEntry<K,V>	queueEnd()	Returns the entry at the end of the queue.
private BoundedConcurrentHashMap.LIRSHashEntry<K,V>	queueFront()	Returns the entry at the front of the queue.
private void	removeFromSegment(Set<BoundedConcurrentHashMap.HashEntry<K,V>> evicted)
private BoundedConcurrentHashMap.LIRSHashEntry<K,V>	stackBottom()	Returns the entry at the bottom of the stack.
BoundedConcurrentHashMap.Eviction	strategy()	Returns type of eviction algorithm (strategy).
boolean	thresholdExpired()	Returns true if batching threshold has expired, false otherwise.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

L_LIRS

private static final float L_LIRS

The percentage of the cache which is dedicated to hot blocks. See section 5.1

See Also:

• Constant Field Values

segment

private final BoundedConcurrentHashMap.Segment<K,V> segment

The owning segment

accessQueue

private final ConcurrentLinkedQueue<BoundedConcurrentHashMap.LIRSHashEntry<K,V>> accessQueue

The accessQueue for reducing lock contention See "BP-Wrapper: a system framework making any replacement algorithms (almost) lock contention free"

http://www.cse.ohio-state.edu/hpcs/WWW/HTML/publications/abs09-1.html

maxBatchQueueSize

private final int maxBatchQueueSize

The maxBatchQueueSize

See "BP-Wrapper: a system framework making any replacement algorithms (almost) lock contention free"

size

private int size

The number of LIRS entries in a segment

batchThresholdFactor

private final float batchThresholdFactor

header

private final BoundedConcurrentHashMap.LIRSHashEntry<K,V> header

This header encompasses two data structures:

• The LIRS stack, S, which is maintains recency information. All hot entries are on the stack. All cold and non-resident entries which are more recent than the least recent hot entry are also stored in the stack (the stack is always pruned such that the last entry is hot, and all entries accessed more recently than the last hot entry are present in the stack). The stack is ordered by recency, with its most recently accessed entry at the top, and its least recently accessed entry at the bottom.
• The LIRS queue, Q, which enqueues all cold entries for eviction. Cold entries (by definition in the queue) may be absent from the stack (due to pruning of the stack). Cold entries are added to the end of the queue and entries are evicted from the front of the queue.

maximumHotSize

private final int maximumHotSize

The maximum number of hot entries (L_lirs in the paper).

maximumSize

private final int maximumSize

The maximum number of resident entries (L in the paper).

hotSize

private int hotSize

The actual number of hot entries.

Constructor Details

LIRS

public LIRS(BoundedConcurrentHashMap.Segment<K,V> s,
 int capacity,
 int maxBatchSize,
 float batchThresholdFactor)

Method Details

calculateLIRSize

private static int calculateLIRSize(int maximumSize)

execute

public Set<BoundedConcurrentHashMap.HashEntry<K,V>> execute()

Description copied from interface: BoundedConcurrentHashMap.EvictionPolicy

Invokes eviction policy algorithm and returns set of evicted entries.

Set cannot be null but could possibly be an empty set.

Specified by:

execute in interface BoundedConcurrentHashMap.EvictionPolicy<K,V>

Returns:

set of evicted entries.

pruneStack

private void pruneStack(Set<BoundedConcurrentHashMap.HashEntry<K,V>> evicted)

Prunes HIR blocks in the bottom of the stack until an HOT block sits in the stack bottom. If pruned blocks were resident, then they remain in the queue; otherwise they are no longer referenced, and are thus removed from the backing map.

onEntryMiss

public Set<BoundedConcurrentHashMap.HashEntry<K,V>> onEntryMiss(BoundedConcurrentHashMap.HashEntry<K,V> en)

Description copied from interface: BoundedConcurrentHashMap.EvictionPolicy

Invoked to notify EvictionPolicy implementation that there has been an attempt to access an entry in Segment, however that entry was not present in Segment.

Specified by:

onEntryMiss in interface BoundedConcurrentHashMap.EvictionPolicy<K,V>

Parameters:

en - accessed entry in Segment

Returns:

non null set of evicted entries.

removeFromSegment

private void removeFromSegment(Set<BoundedConcurrentHashMap.HashEntry<K,V>> evicted)

onEntryHit

public boolean onEntryHit(BoundedConcurrentHashMap.HashEntry<K,V> e)

Description copied from interface: BoundedConcurrentHashMap.EvictionPolicy

Invoked to notify EvictionPolicy implementation that an entry in Segment has been accessed. Returns true if batching threshold has been reached, false otherwise.

Note that this method is potentially invoked without holding a lock on Segment.

Specified by:

onEntryHit in interface BoundedConcurrentHashMap.EvictionPolicy<K,V>

Parameters:

e - accessed entry in Segment

Returns:

true if batching threshold has been reached, false otherwise.

thresholdExpired

public boolean thresholdExpired()

Description copied from interface: BoundedConcurrentHashMap.EvictionPolicy

Returns true if batching threshold has expired, false otherwise.

Note that this method is potentially invoked without holding a lock on Segment.

Specified by:

thresholdExpired in interface BoundedConcurrentHashMap.EvictionPolicy<K,V>

Returns:

true if batching threshold has expired, false otherwise.

onEntryRemove

public void onEntryRemove(BoundedConcurrentHashMap.HashEntry<K,V> e)

Description copied from interface: BoundedConcurrentHashMap.EvictionPolicy

Invoked to notify EvictionPolicy implementation that an entry e has been removed from Segment.

Specified by:

onEntryRemove in interface BoundedConcurrentHashMap.EvictionPolicy<K,V>

Parameters:

e - removed entry in Segment

clear

public void clear()

Description copied from interface: BoundedConcurrentHashMap.EvictionPolicy

Invoked to notify EvictionPolicy implementation that all Segment entries have been cleared.

Specified by:

clear in interface BoundedConcurrentHashMap.EvictionPolicy<K,V>

strategy

public BoundedConcurrentHashMap.Eviction strategy()

Description copied from interface: BoundedConcurrentHashMap.EvictionPolicy

Returns type of eviction algorithm (strategy).

Specified by:

strategy in interface BoundedConcurrentHashMap.EvictionPolicy<K,V>

Returns:

type of eviction algorithm

stackBottom

private BoundedConcurrentHashMap.LIRSHashEntry<K,V> stackBottom()

Returns the entry at the bottom of the stack.

queueFront

private BoundedConcurrentHashMap.LIRSHashEntry<K,V> queueFront()

Returns the entry at the front of the queue.

queueEnd

private BoundedConcurrentHashMap.LIRSHashEntry<K,V> queueEnd()

Returns the entry at the end of the queue.

createNewEntry

public BoundedConcurrentHashMap.HashEntry<K,V> createNewEntry(K key,
 int hash,
 BoundedConcurrentHashMap.HashEntry<K,V> next,
 V value)

Specified by:

createNewEntry in interface BoundedConcurrentHashMap.EvictionPolicy<K,V>