--- jsr166/src/jsr166e/ConcurrentHashMapV8.java 2012/07/04 20:21:02 1.43
+++ jsr166/src/jsr166e/ConcurrentHashMapV8.java 2013/02/15 22:20:46 1.99
@@ -5,7 +5,8 @@
*/
package jsr166e;
-import jsr166e.LongAdder;
+
+import java.util.Comparator;
import java.util.Arrays;
import java.util.Map;
import java.util.Set;
@@ -20,9 +21,9 @@ import java.util.Enumeration;
import java.util.ConcurrentModificationException;
import java.util.NoSuchElementException;
import java.util.concurrent.ConcurrentMap;
-import java.util.concurrent.ThreadLocalRandom;
-import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
import java.io.Serializable;
/**
@@ -37,25 +38,28 @@ import java.io.Serializable;
* interoperable with {@code Hashtable} in programs that rely on its
* thread safety but not on its synchronization details.
*
- * Retrieval operations (including {@code get}) generally do not
+ *
Retrieval operations (including {@code get}) generally do not
* block, so may overlap with update operations (including {@code put}
* and {@code remove}). Retrievals reflect the results of the most
* recently completed update operations holding upon their
- * onset. For aggregate operations such as {@code putAll} and {@code
- * clear}, concurrent retrievals may reflect insertion or removal of
- * only some entries. Similarly, Iterators and Enumerations return
- * elements reflecting the state of the hash table at some point at or
- * since the creation of the iterator/enumeration. They do
- * not throw {@link ConcurrentModificationException}.
- * However, iterators are designed to be used by only one thread at a
- * time. Bear in mind that the results of aggregate status methods
- * including {@code size}, {@code isEmpty}, and {@code containsValue}
- * are typically useful only when a map is not undergoing concurrent
- * updates in other threads. Otherwise the results of these methods
- * reflect transient states that may be adequate for monitoring
- * or estimation purposes, but not for program control.
+ * onset. (More formally, an update operation for a given key bears a
+ * happens-before relation with any (non-null) retrieval for
+ * that key reporting the updated value.) For aggregate operations
+ * such as {@code putAll} and {@code clear}, concurrent retrievals may
+ * reflect insertion or removal of only some entries. Similarly,
+ * Iterators and Enumerations return elements reflecting the state of
+ * the hash table at some point at or since the creation of the
+ * iterator/enumeration. They do not throw {@link
+ * ConcurrentModificationException}. However, iterators are designed
+ * to be used by only one thread at a time. Bear in mind that the
+ * results of aggregate status methods including {@code size}, {@code
+ * isEmpty}, and {@code containsValue} are typically useful only when
+ * a map is not undergoing concurrent updates in other threads.
+ * Otherwise the results of these methods reflect transient states
+ * that may be adequate for monitoring or estimation purposes, but not
+ * for program control.
*
- *
The table is dynamically expanded when there are too many
+ *
The table is dynamically expanded when there are too many
* collisions (i.e., keys that have distinct hash codes but fall into
* the same slot modulo the table size), with the expected average
* effect of maintaining roughly two bins per mapping (corresponding
@@ -76,68 +80,150 @@ import java.io.Serializable;
* {@code hashCode()} is a sure way to slow down performance of any
* hash table.
*
+ *
A {@link Set} projection of a ConcurrentHashMapV8 may be created
+ * (using {@link #newKeySet()} or {@link #newKeySet(int)}), or viewed
+ * (using {@link #keySet(Object)} when only keys are of interest, and the
+ * mapped values are (perhaps transiently) not used or all take the
+ * same mapping value.
+ *
+ *
A ConcurrentHashMapV8 can be used as scalable frequency map (a
+ * form of histogram or multiset) by using {@link LongAdder} values
+ * and initializing via {@link #computeIfAbsent}. For example, to add
+ * a count to a {@code ConcurrentHashMapV8 freqs}, you
+ * can use {@code freqs.computeIfAbsent(k -> new
+ * LongAdder()).increment();}
+ *
* This class and its views and iterators implement all of the
* optional methods of the {@link Map} and {@link Iterator}
* interfaces.
*
- *
Like {@link Hashtable} but unlike {@link HashMap}, this class
+ *
Like {@link Hashtable} but unlike {@link HashMap}, this class
* does not allow {@code null} to be used as a key or value.
*
+ *
ConcurrentHashMapV8s support sequential and parallel operations
+ * bulk operations. (Parallel forms use the {@link
+ * ForkJoinPool#commonPool()}). Tasks that may be used in other
+ * contexts are available in class {@link ForkJoinTasks}. These
+ * operations are designed to be safely, and often sensibly, applied
+ * even with maps that are being concurrently updated by other
+ * threads; for example, when computing a snapshot summary of the
+ * values in a shared registry. There are three kinds of operation,
+ * each with four forms, accepting functions with Keys, Values,
+ * Entries, and (Key, Value) arguments and/or return values. Because
+ * the elements of a ConcurrentHashMapV8 are not ordered in any
+ * particular way, and may be processed in different orders in
+ * different parallel executions, the correctness of supplied
+ * functions should not depend on any ordering, or on any other
+ * objects or values that may transiently change while computation is
+ * in progress; and except for forEach actions, should ideally be
+ * side-effect-free.
+ *
+ *
+ * - forEach: Perform a given action on each element.
+ * A variant form applies a given transformation on each element
+ * before performing the action.
+ *
+ * - search: Return the first available non-null result of
+ * applying a given function on each element; skipping further
+ * search when a result is found.
+ *
+ * - reduce: Accumulate each element. The supplied reduction
+ * function cannot rely on ordering (more formally, it should be
+ * both associative and commutative). There are five variants:
+ *
+ *
+ *
+ * - Plain reductions. (There is not a form of this method for
+ * (key, value) function arguments since there is no corresponding
+ * return type.)
+ *
+ * - Mapped reductions that accumulate the results of a given
+ * function applied to each element.
+ *
+ * - Reductions to scalar doubles, longs, and ints, using a
+ * given basis value.
+ *
+ *
+ *
+ *
+ *
+ * The concurrency properties of bulk operations follow
+ * from those of ConcurrentHashMapV8: Any non-null result returned
+ * from {@code get(key)} and related access methods bears a
+ * happens-before relation with the associated insertion or
+ * update. The result of any bulk operation reflects the
+ * composition of these per-element relations (but is not
+ * necessarily atomic with respect to the map as a whole unless it
+ * is somehow known to be quiescent). Conversely, because keys
+ * and values in the map are never null, null serves as a reliable
+ * atomic indicator of the current lack of any result. To
+ * maintain this property, null serves as an implicit basis for
+ * all non-scalar reduction operations. For the double, long, and
+ * int versions, the basis should be one that, when combined with
+ * any other value, returns that other value (more formally, it
+ * should be the identity element for the reduction). Most common
+ * reductions have these properties; for example, computing a sum
+ * with basis 0 or a minimum with basis MAX_VALUE.
+ *
+ *
Search and transformation functions provided as arguments
+ * should similarly return null to indicate the lack of any result
+ * (in which case it is not used). In the case of mapped
+ * reductions, this also enables transformations to serve as
+ * filters, returning null (or, in the case of primitive
+ * specializations, the identity basis) if the element should not
+ * be combined. You can create compound transformations and
+ * filterings by composing them yourself under this "null means
+ * there is nothing there now" rule before using them in search or
+ * reduce operations.
+ *
+ *
Methods accepting and/or returning Entry arguments maintain
+ * key-value associations. They may be useful for example when
+ * finding the key for the greatest value. Note that "plain" Entry
+ * arguments can be supplied using {@code new
+ * AbstractMap.SimpleEntry(k,v)}.
+ *
+ *
Bulk operations may complete abruptly, throwing an
+ * exception encountered in the application of a supplied
+ * function. Bear in mind when handling such exceptions that other
+ * concurrently executing functions could also have thrown
+ * exceptions, or would have done so if the first exception had
+ * not occurred.
+ *
+ *
Speedups for parallel compared to sequential forms are common
+ * but not guaranteed. Parallel operations involving brief functions
+ * on small maps may execute more slowly than sequential forms if the
+ * underlying work to parallelize the computation is more expensive
+ * than the computation itself. Similarly, parallelization may not
+ * lead to much actual parallelism if all processors are busy
+ * performing unrelated tasks.
+ *
+ *
All arguments to all task methods must be non-null.
+ *
+ *
jsr166e note: During transition, this class
+ * uses nested functional interfaces with different names but the
+ * same forms as those expected for JDK8.
+ *
*
This class is a member of the
*
* Java Collections Framework.
*
- *
jsr166e note: This class is a candidate replacement for
- * java.util.concurrent.ConcurrentHashMap.
- *
* @since 1.5
* @author Doug Lea
* @param the type of keys maintained by this map
* @param the type of mapped values
*/
-public class ConcurrentHashMapV8
- implements ConcurrentMap, Serializable {
+public class ConcurrentHashMapV8
+ implements ConcurrentMap, Serializable {
private static final long serialVersionUID = 7249069246763182397L;
/**
- * A function computing a mapping from the given key to a value.
- * This is a place-holder for an upcoming JDK8 interface.
- */
- public static interface MappingFunction {
- /**
- * Returns a value for the given key, or null if there is no mapping.
- *
- * @param key the (non-null) key
- * @return a value for the key, or null if none
- */
- V map(K key);
- }
-
- /**
- * A function computing a new mapping given a key and its current
- * mapped value (or {@code null} if there is no current
- * mapping). This is a place-holder for an upcoming JDK8
- * interface.
- */
- public static interface RemappingFunction {
- /**
- * Returns a new value given a key and its current value.
- *
- * @param key the (non-null) key
- * @param value the current value, or null if there is no mapping
- * @return a value for the key, or null if none
- */
- V remap(K key, V value);
- }
-
- /**
* A partitionable iterator. A Spliterator can be traversed
* directly, but can also be partitioned (before traversal) by
* creating another Spliterator that covers a non-overlapping
* portion of the elements, and so may be amenable to parallel
* execution.
*
- * This interface exports a subset of expected JDK8
+ *
This interface exports a subset of expected JDK8
* functionality.
*
*
Sample usage: Here is one (of the several) ways to compute
@@ -145,18 +231,20 @@ public class ConcurrentHashMapV8
* framework. As illustrated here, Spliterators are well suited to
* designs in which a task repeatedly splits off half its work
* into forked subtasks until small enough to process directly,
- * and then joins these subtasks. Variants of this style can be
- * also be used in completion-based designs.
+ * and then joins these subtasks. Variants of this style can also
+ * be used in completion-based designs.
*
*
* {@code ConcurrentHashMapV8 m = ...
- * // Uses parallel depth of log2 of size / (parallelism * slack of 8).
- * int depth = 32 - Integer.numberOfLeadingZeros(m.size() / (aForkJoinPool.getParallelism() * 8));
- * long sum = aForkJoinPool.invoke(new SumValues(m.valueSpliterator(), depth, null));
+ * // split as if have 8 * parallelism, for load balance
+ * int n = m.size();
+ * int p = aForkJoinPool.getParallelism() * 8;
+ * int split = (n < p)? n : p;
+ * long sum = aForkJoinPool.invoke(new SumValues(m.valueSpliterator(), split, null));
* // ...
* static class SumValues extends RecursiveTask {
* final Spliterator s;
- * final int depth; // number of splits before processing
+ * final int split; // split while > 1
* final SumValues nextJoin; // records forked subtasks to join
* SumValues(Spliterator s, int depth, SumValues nextJoin) {
* this.s = s; this.depth = depth; this.nextJoin = nextJoin;
@@ -164,8 +252,8 @@ public class ConcurrentHashMapV8
* public Long compute() {
* long sum = 0;
* SumValues subtasks = null; // fork subtasks
- * for (int d = depth - 1; d >= 0; --d)
- * (subtasks = new SumValues(s.split(), d, subtasks)).fork();
+ * for (int s = split >>> 1; s > 0; s >>>= 1)
+ * (subtasks = new SumValues(s.split(), s, subtasks)).fork();
* while (s.hasNext()) // directly process remaining elements
* sum += s.next();
* for (SumValues t = subtasks; t != null; t = t.nextJoin)
@@ -192,21 +280,9 @@ public class ConcurrentHashMapV8
* @return a Spliterator covering approximately half of the
* elements
* @throws IllegalStateException if this Spliterator has
- * already commenced traversing elements.
+ * already commenced traversing elements
*/
Spliterator split();
-
- /**
- * Returns a Spliterator producing the same elements as this
- * Spliterator. This method may be used for example to create
- * a second Spliterator before a traversal, in order to later
- * perform a second traversal.
- *
- * @return a Spliterator covering the same range as this Spliterator.
- * @throws IllegalStateException if this Spliterator has
- * already commenced traversing elements.
- */
- Spliterator clone();
}
/*
@@ -219,17 +295,15 @@ public class ConcurrentHashMapV8
* the same or better than java.util.HashMap, and to support high
* initial insertion rates on an empty table by many threads.
*
- * Each key-value mapping is held in a Node. Because Node fields
- * can contain special values, they are defined using plain Object
- * types. Similarly in turn, all internal methods that use them
- * work off Object types. And similarly, so do the internal
- * methods of auxiliary iterator and view classes. All public
- * generic typed methods relay in/out of these internal methods,
- * supplying null-checks and casts as needed. This also allows
- * many of the public methods to be factored into a smaller number
- * of internal methods (although sadly not so for the five
- * variants of put-related operations). The validation-based
- * approach explained below leads to a lot of code sprawl because
+ * Each key-value mapping is held in a Node. Because Node key
+ * fields can contain special values, they are defined using plain
+ * Object types (not type "K"). This leads to a lot of explicit
+ * casting (and many explicit warning suppressions to tell
+ * compilers not to complain about it). It also allows some of the
+ * public methods to be factored into a smaller number of internal
+ * methods (although sadly not so for the five variants of
+ * put-related operations). The validation-based approach
+ * explained below leads to a lot of code sprawl because
* retry-control precludes factoring into smaller methods.
*
* The table is lazily initialized to a power-of-two size upon the
@@ -243,19 +317,12 @@ public class ConcurrentHashMapV8
* as lookups check hash code and non-nullness of value before
* checking key equality.
*
- * We use the top two bits of Node hash fields for control
- * purposes -- they are available anyway because of addressing
- * constraints. As explained further below, these top bits are
- * used as follows:
- * 00 - Normal
- * 01 - Locked
- * 11 - Locked and may have a thread waiting for lock
- * 10 - Node is a forwarding node
- *
- * The lower 30 bits of each Node's hash field contain a
- * transformation of the key's hash code, except for forwarding
- * nodes, for which the lower bits are zero (and so always have
- * hash field == MOVED).
+ * We use the top (sign) bit of Node hash fields for control
+ * purposes -- it is available anyway because of addressing
+ * constraints. Nodes with negative hash fields are forwarding
+ * nodes to either TreeBins or resized tables. The lower 31 bits
+ * of each normal Node's hash field contain a transformation of
+ * the key's hash code.
*
* Insertion (via put or its variants) of the first node in an
* empty bin is performed by just CASing it to the bin. This is
@@ -264,12 +331,8 @@ public class ConcurrentHashMapV8
* delete, and replace) require locks. We do not want to waste
* the space required to associate a distinct lock object with
* each bin, so instead use the first node of a bin list itself as
- * a lock. Blocking support for these locks relies on the builtin
- * "synchronized" monitors. However, we also need a tryLock
- * construction, so we overlay these by using bits of the Node
- * hash field for lock control (see above), and so normally use
- * builtin monitors only for blocking and signalling using
- * wait/notifyAll constructions. See Node.tryAwaitLock.
+ * a lock. Locking support for these locks relies on builtin
+ * "synchronized" monitors.
*
* Using the first node of a list as a lock does not by itself
* suffice though: When a node is locked, any update must first
@@ -331,46 +394,46 @@ public class ConcurrentHashMapV8
* iterators in the same way.
*
* The table is resized when occupancy exceeds a percentage
- * threshold (nominally, 0.75, but see below). Only a single
- * thread performs the resize (using field "sizeCtl", to arrange
- * exclusion), but the table otherwise remains usable for reads
- * and updates. Resizing proceeds by transferring bins, one by
- * one, from the table to the next table. Because we are using
- * power-of-two expansion, the elements from each bin must either
- * stay at same index, or move with a power of two offset. We
- * eliminate unnecessary node creation by catching cases where old
- * nodes can be reused because their next fields won't change. On
- * average, only about one-sixth of them need cloning when a table
- * doubles. The nodes they replace will be garbage collectable as
- * soon as they are no longer referenced by any reader thread that
- * may be in the midst of concurrently traversing table. Upon
- * transfer, the old table bin contains only a special forwarding
- * node (with hash field "MOVED") that contains the next table as
- * its key. On encountering a forwarding node, access and update
- * operations restart, using the new table.
- *
- * Each bin transfer requires its bin lock. However, unlike other
- * cases, a transfer can skip a bin if it fails to acquire its
- * lock, and revisit it later (unless it is a TreeBin). Method
- * rebuild maintains a buffer of TRANSFER_BUFFER_SIZE bins that
- * have been skipped because of failure to acquire a lock, and
- * blocks only if none are available (i.e., only very rarely).
- * The transfer operation must also ensure that all accessible
- * bins in both the old and new table are usable by any traversal.
- * When there are no lock acquisition failures, this is arranged
- * simply by proceeding from the last bin (table.length - 1) up
- * towards the first. Upon seeing a forwarding node, traversals
- * (see class InternalIterator) arrange to move to the new table
- * without revisiting nodes. However, when any node is skipped
- * during a transfer, all earlier table bins may have become
- * visible, so are initialized with a reverse-forwarding node back
- * to the old table until the new ones are established. (This
- * sometimes requires transiently locking a forwarding node, which
- * is possible under the above encoding.) These more expensive
- * mechanics trigger only when necessary.
+ * threshold (nominally, 0.75, but see below). Any thread
+ * noticing an overfull bin may assist in resizing after the
+ * initiating thread allocates and sets up the replacement
+ * array. However, rather than stalling, these other threads may
+ * proceed with insertions etc. The use of TreeBins shields us
+ * from the worst case effects of overfilling while resizes are in
+ * progress. Resizing proceeds by transferring bins, one by one,
+ * from the table to the next table. To enable concurrency, the
+ * next table must be (incrementally) prefilled with place-holders
+ * serving as reverse forwarders to the old table. Because we are
+ * using power-of-two expansion, the elements from each bin must
+ * either stay at same index, or move with a power of two
+ * offset. We eliminate unnecessary node creation by catching
+ * cases where old nodes can be reused because their next fields
+ * won't change. On average, only about one-sixth of them need
+ * cloning when a table doubles. The nodes they replace will be
+ * garbage collectable as soon as they are no longer referenced by
+ * any reader thread that may be in the midst of concurrently
+ * traversing table. Upon transfer, the old table bin contains
+ * only a special forwarding node (with hash field "MOVED") that
+ * contains the next table as its key. On encountering a
+ * forwarding node, access and update operations restart, using
+ * the new table.
+ *
+ * Each bin transfer requires its bin lock, which can stall
+ * waiting for locks while resizing. However, because other
+ * threads can join in and help resize rather than contend for
+ * locks, average aggregate waits become shorter as resizing
+ * progresses. The transfer operation must also ensure that all
+ * accessible bins in both the old and new table are usable by any
+ * traversal. This is arranged by proceeding from the last bin
+ * (table.length - 1) up towards the first. Upon seeing a
+ * forwarding node, traversals (see class Traverser) arrange to
+ * move to the new table without revisiting nodes. However, to
+ * ensure that no intervening nodes are skipped, bin splitting can
+ * only begin after the associated reverse-forwarders are in
+ * place.
*
* The traversal scheme also applies to partial traversals of
- * ranges of bins (via an alternate InternalIterator constructor)
+ * ranges of bins (via an alternate Traverser constructor)
* to support partitioned aggregate operations. Also, read-only
* operations give up if ever forwarded to a null table, which
* provides support for shutdown-style clearing, which is also not
@@ -382,20 +445,20 @@ public class ConcurrentHashMapV8
* These cases attempt to override the initial capacity settings,
* but harmlessly fail to take effect in cases of races.
*
- * The element count is maintained using a LongAdder, which avoids
- * contention on updates but can encounter cache thrashing if read
- * too frequently during concurrent access. To avoid reading so
- * often, resizing is attempted either when a bin lock is
- * contended, or upon adding to a bin already holding two or more
- * nodes (checked before adding in the xIfAbsent methods, after
- * adding in others). Under uniform hash distributions, the
- * probability of this occurring at threshold is around 13%,
- * meaning that only about 1 in 8 puts check threshold (and after
- * resizing, many fewer do so). But this approximation has high
- * variance for small table sizes, so we check on any collision
- * for sizes <= 64. The bulk putAll operation further reduces
- * contention by only committing count updates upon these size
- * checks.
+ * The element count is maintained using a specialization of
+ * LongAdder. We need to incorporate a specialization rather than
+ * just use a LongAdder in order to access implicit
+ * contention-sensing that leads to creation of multiple
+ * CounterCells. The counter mechanics avoid contention on
+ * updates but can encounter cache thrashing if read too
+ * frequently during concurrent access. To avoid reading so often,
+ * resizing under contention is attempted only upon adding to a
+ * bin already holding two or more nodes. Under uniform hash
+ * distributions, the probability of this occurring at threshold
+ * is around 13%, meaning that only about 1 in 8 puts check
+ * threshold (and after resizing, many fewer do so). The bulk
+ * putAll operation further reduces contention by only committing
+ * count updates upon these size checks.
*
* Maintaining API and serialization compatibility with previous
* versions of this class introduces several oddities. Mainly: We
@@ -446,27 +509,68 @@ public class ConcurrentHashMapV8
private static final float LOAD_FACTOR = 0.75f;
/**
- * The buffer size for skipped bins during transfers. The
- * value is arbitrary but should be large enough to avoid
- * most locking stalls during resizes.
- */
- private static final int TRANSFER_BUFFER_SIZE = 32;
-
- /**
* The bin count threshold for using a tree rather than list for a
* bin. The value reflects the approximate break-even point for
* using tree-based operations.
*/
private static final int TREE_THRESHOLD = 8;
+ /**
+ * Minimum number of rebinnings per transfer step. Ranges are
+ * subdivided to allow multiple resizer threads. This value
+ * serves as a lower bound to avoid resizers encountering
+ * excessive memory contention. The value should be at least
+ * DEFAULT_CAPACITY.
+ */
+ private static final int MIN_TRANSFER_STRIDE = 16;
+
/*
- * Encodings for special uses of Node hash fields. See above for
- * explanation.
+ * Encodings for Node hash fields. See above for explanation.
*/
static final int MOVED = 0x80000000; // hash field for forwarding nodes
- static final int LOCKED = 0x40000000; // set/tested only as a bit
- static final int WAITING = 0xc0000000; // both bits set/tested together
- static final int HASH_BITS = 0x3fffffff; // usable bits of normal node hash
+ static final int HASH_BITS = 0x7fffffff; // usable bits of normal node hash
+
+ /** Number of CPUS, to place bounds on some sizings */
+ static final int NCPU = Runtime.getRuntime().availableProcessors();
+
+ /* ---------------- Counters -------------- */
+
+ // Adapted from LongAdder and Striped64.
+ // See their internal docs for explanation.
+
+ // A padded cell for distributing counts
+ static final class CounterCell {
+ volatile long p0, p1, p2, p3, p4, p5, p6;
+ volatile long value;
+ volatile long q0, q1, q2, q3, q4, q5, q6;
+ CounterCell(long x) { value = x; }
+ }
+
+ /**
+ * Holder for the thread-local hash code determining which
+ * CounterCell to use. The code is initialized via the
+ * counterHashCodeGenerator, but may be moved upon collisions.
+ */
+ static final class CounterHashCode {
+ int code;
+ }
+
+ /**
+ * Generates initial value for per-thread CounterHashCodes
+ */
+ static final AtomicInteger counterHashCodeGenerator = new AtomicInteger();
+
+ /**
+ * Increment for counterHashCodeGenerator. See class ThreadLocal
+ * for explanation.
+ */
+ static final int SEED_INCREMENT = 0x61c88647;
+
+ /**
+ * Per-thread counter hash codes. Shared across all instances.
+ */
+ static final ThreadLocal threadCounterHashCode =
+ new ThreadLocal();
/* ---------------- Fields -------------- */
@@ -474,26 +578,54 @@ public class ConcurrentHashMapV8
* The array of bins. Lazily initialized upon first insertion.
* Size is always a power of two. Accessed directly by iterators.
*/
- transient volatile Node[] table;
+ transient volatile Node[] table;
+
+ /**
+ * The next table to use; non-null only while resizing.
+ */
+ private transient volatile Node[] nextTable;
/**
- * The counter maintaining number of elements.
+ * Base counter value, used mainly when there is no contention,
+ * but also as a fallback during table initialization
+ * races. Updated via CAS.
*/
- private transient final LongAdder counter;
+ private transient volatile long baseCount;
/**
* Table initialization and resizing control. When negative, the
- * table is being initialized or resized. Otherwise, when table is
- * null, holds the initial table size to use upon creation, or 0
- * for default. After initialization, holds the next element count
- * value upon which to resize the table.
+ * table is being initialized or resized: -1 for initialization,
+ * else -(1 + the number of active resizing threads). Otherwise,
+ * when table is null, holds the initial table size to use upon
+ * creation, or 0 for default. After initialization, holds the
+ * next element count value upon which to resize the table.
*/
private transient volatile int sizeCtl;
+ /**
+ * The next table index (plus one) to split while resizing.
+ */
+ private transient volatile int transferIndex;
+
+ /**
+ * The least available table index to split while resizing.
+ */
+ private transient volatile int transferOrigin;
+
+ /**
+ * Spinlock (locked via CAS) used when resizing and/or creating Cells.
+ */
+ private transient volatile int counterBusy;
+
+ /**
+ * Table of counter cells. When non-null, size is a power of 2.
+ */
+ private transient volatile CounterCell[] counterCells;
+
// views
- private transient KeySet keySet;
- private transient Values values;
- private transient EntrySet entrySet;
+ private transient KeySetView keySet;
+ private transient ValuesView values;
+ private transient EntrySetView entrySet;
/** For serialization compatibility. Null unless serialized; see below */
private Segment[] segments;
@@ -512,16 +644,19 @@ public class ConcurrentHashMapV8
* inline assignments below.
*/
- static final Node tabAt(Node[] tab, int i) { // used by InternalIterator
- return (Node)UNSAFE.getObjectVolatile(tab, ((long)i< Node tabAt
+ (Node[] tab, int i) { // used by Traverser
+ return (Node)U.getObjectVolatile(tab, ((long)i << ASHIFT) + ABASE);
}
- private static final boolean casTabAt(Node[] tab, int i, Node c, Node v) {
- return UNSAFE.compareAndSwapObject(tab, ((long)i< boolean casTabAt
+ (Node[] tab, int i, Node c, Node v) {
+ return U.compareAndSwapObject(tab, ((long)i << ASHIFT) + ABASE, c, v);
}
- private static final void setTabAt(Node[] tab, int i, Node v) {
- UNSAFE.putObjectVolatile(tab, ((long)i< void setTabAt
+ (Node[] tab, int i, Node v) {
+ U.putObjectVolatile(tab, ((long)i << ASHIFT) + ABASE, v);
}
/* ---------------- Nodes -------------- */
@@ -536,84 +671,18 @@ public class ConcurrentHashMapV8
* before a val, but can only be used after checking val to be
* non-null.
*/
- static class Node {
- volatile int hash;
+ static class Node {
+ final int hash;
final Object key;
- volatile Object val;
- volatile Node next;
+ volatile V val;
+ volatile Node next;
- Node(int hash, Object key, Object val, Node next) {
+ Node(int hash, Object key, V val, Node next) {
this.hash = hash;
this.key = key;
this.val = val;
this.next = next;
}
-
- /** CompareAndSet the hash field */
- final boolean casHash(int cmp, int val) {
- return UNSAFE.compareAndSwapInt(this, hashOffset, cmp, val);
- }
-
- /** The number of spins before blocking for a lock */
- static final int MAX_SPINS =
- Runtime.getRuntime().availableProcessors() > 1 ? 64 : 1;
-
- /**
- * Spins a while if LOCKED bit set and this node is the first
- * of its bin, and then sets WAITING bits on hash field and
- * blocks (once) if they are still set. It is OK for this
- * method to return even if lock is not available upon exit,
- * which enables these simple single-wait mechanics.
- *
- * The corresponding signalling operation is performed within
- * callers: Upon detecting that WAITING has been set when
- * unlocking lock (via a failed CAS from non-waiting LOCKED
- * state), unlockers acquire the sync lock and perform a
- * notifyAll.
- */
- final void tryAwaitLock(Node[] tab, int i) {
- if (tab != null && i >= 0 && i < tab.length) { // bounds check
- int r = ThreadLocalRandom.current().nextInt(); // randomize spins
- int spins = MAX_SPINS, h;
- while (tabAt(tab, i) == this && ((h = hash) & LOCKED) != 0) {
- if (spins >= 0) {
- r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
- if (r >= 0 && --spins == 0)
- Thread.yield(); // yield before block
- }
- else if (casHash(h, h | WAITING)) {
- synchronized (this) {
- if (tabAt(tab, i) == this &&
- (hash & WAITING) == WAITING) {
- try {
- wait();
- } catch (InterruptedException ie) {
- Thread.currentThread().interrupt();
- }
- }
- else
- notifyAll(); // possibly won race vs signaller
- }
- break;
- }
- }
- }
- }
-
- // Unsafe mechanics for casHash
- private static final sun.misc.Unsafe UNSAFE;
- private static final long hashOffset;
-
- static {
- try {
- UNSAFE = getUnsafe();
- Class k = Node.class;
- hashOffset = UNSAFE.objectFieldOffset
- (k.getDeclaredField("hash"));
- } catch (Exception e) {
- throw new Error(e);
- }
- }
}
/* ---------------- TreeBins -------------- */
@@ -621,14 +690,14 @@ public class ConcurrentHashMapV8
/**
* Nodes for use in TreeBins
*/
- static final class TreeNode extends Node {
- TreeNode parent; // red-black tree links
- TreeNode left;
- TreeNode right;
- TreeNode prev; // needed to unlink next upon deletion
+ static final class TreeNode extends Node {
+ TreeNode parent; // red-black tree links
+ TreeNode left;
+ TreeNode right;
+ TreeNode prev; // needed to unlink next upon deletion
boolean red;
- TreeNode(int hash, Object key, Object val, Node next, TreeNode parent) {
+ TreeNode(int hash, Object key, V val, Node next, TreeNode parent) {
super(hash, key, val, next);
this.parent = parent;
}
@@ -660,7 +729,7 @@ public class ConcurrentHashMapV8
* TreeBins also maintain a separate locking discipline than
* regular bins. Because they are forwarded via special MOVED
* nodes at bin heads (which can never change once established),
- * we cannot use use those nodes as locks. Instead, TreeBin
+ * we cannot use those nodes as locks. Instead, TreeBin
* extends AbstractQueuedSynchronizer to support a simple form of
* read-write lock. For update operations and table validation,
* the exclusive form of lock behaves in the same way as bin-head
@@ -677,10 +746,10 @@ public class ConcurrentHashMapV8
* and writers. Since we don't need to export full Lock API, we
* just override the minimal AQS methods and use them directly.
*/
- static final class TreeBin extends AbstractQueuedSynchronizer {
+ static final class TreeBin extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 2249069246763182397L;
- transient TreeNode root; // root of tree
- transient TreeNode first; // head of next-pointer list
+ transient TreeNode root; // root of tree
+ transient TreeNode first; // head of next-pointer list
/* AQS overrides */
public final boolean isHeldExclusively() { return getState() > 0; }
@@ -711,9 +780,9 @@ public class ConcurrentHashMapV8
}
/** From CLR */
- private void rotateLeft(TreeNode p) {
+ private void rotateLeft(TreeNode p) {
if (p != null) {
- TreeNode r = p.right, pp, rl;
+ TreeNode r = p.right, pp, rl;
if ((rl = p.right = r.left) != null)
rl.parent = p;
if ((pp = r.parent = p.parent) == null)
@@ -728,9 +797,9 @@ public class ConcurrentHashMapV8
}
/** From CLR */
- private void rotateRight(TreeNode p) {
+ private void rotateRight(TreeNode p) {
if (p != null) {
- TreeNode l = p.left, pp, lr;
+ TreeNode l = p.left, pp, lr;
if ((lr = p.left = l.right) != null)
lr.parent = p;
if ((pp = l.parent = p.parent) == null)
@@ -745,11 +814,11 @@ public class ConcurrentHashMapV8
}
/**
- * Return the TreeNode (or null if not found) for the given key
+ * Returns the TreeNode (or null if not found) for the given key
* starting at given root.
*/
- @SuppressWarnings("unchecked") // suppress Comparable cast warning
- final TreeNode getTreeNode(int h, Object k, TreeNode p) {
+ @SuppressWarnings("unchecked") final TreeNode getTreeNode
+ (int h, Object k, TreeNode p) {
Class c = k.getClass();
while (p != null) {
int dir, ph; Object pk; Class pc;
@@ -759,16 +828,17 @@ public class ConcurrentHashMapV8
if (c != (pc = pk.getClass()) ||
!(k instanceof Comparable) ||
(dir = ((Comparable)k).compareTo((Comparable)pk)) == 0) {
- dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
- TreeNode r = null, s = null, pl, pr;
- if (dir >= 0) {
- if ((pl = p.left) != null && h <= pl.hash)
- s = pl;
+ if ((dir = (c == pc) ? 0 :
+ c.getName().compareTo(pc.getName())) == 0) {
+ TreeNode r = null, pl, pr; // check both sides
+ if ((pr = p.right) != null && h >= pr.hash &&
+ (r = getTreeNode(h, k, pr)) != null)
+ return r;
+ else if ((pl = p.left) != null && h <= pl.hash)
+ dir = -1;
+ else // nothing there
+ return null;
}
- else if ((pr = p.right) != null && h >= pr.hash)
- s = pr;
- if (s != null && (r = getTreeNode(h, k, s)) != null)
- return r;
}
}
else
@@ -783,10 +853,10 @@ public class ConcurrentHashMapV8
* read-lock to call getTreeNode, but during failure to get
* lock, searches along next links.
*/
- final Object getValue(int h, Object k) {
- Node r = null;
+ final V getValue(int h, Object k) {
+ Node r = null;
int c = getState(); // Must read lock state first
- for (Node e = first; e != null; e = e.next) {
+ for (Node e = first; e != null; e = e.next) {
if (c <= 0 && compareAndSetState(c, c - 1)) {
try {
r = getTreeNode(h, k, root);
@@ -795,7 +865,7 @@ public class ConcurrentHashMapV8
}
break;
}
- else if ((e.hash & HASH_BITS) == h && k.equals(e.key)) {
+ else if (e.hash == h && k.equals(e.key)) {
r = e;
break;
}
@@ -806,13 +876,13 @@ public class ConcurrentHashMapV8
}
/**
- * Find or add a node
+ * Finds or adds a node.
* @return null if added
*/
- @SuppressWarnings("unchecked") // suppress Comparable cast warning
- final TreeNode putTreeNode(int h, Object k, Object v) {
+ @SuppressWarnings("unchecked") final TreeNode putTreeNode
+ (int h, Object k, V v) {
Class c = k.getClass();
- TreeNode pp = root, p = null;
+ TreeNode pp = root, p = null;
int dir = 0;
while (pp != null) { // find existing node or leaf to insert at
int ph; Object pk; Class pc;
@@ -823,11 +893,14 @@ public class ConcurrentHashMapV8
if (c != (pc = pk.getClass()) ||
!(k instanceof Comparable) ||
(dir = ((Comparable)k).compareTo((Comparable)pk)) == 0) {
- dir = (c == pc) ? 0 : c.getName().compareTo(pc.getName());
- TreeNode r = null, s = null, pl, pr;
- if (dir >= 0) {
- if ((pl = p.left) != null && h <= pl.hash)
- s = pl;
+ TreeNode s = null, r = null, pr;
+ if ((dir = (c == pc) ? 0 :
+ c.getName().compareTo(pc.getName())) == 0) {
+ if ((pr = p.right) != null && h >= pr.hash &&
+ (r = getTreeNode(h, k, pr)) != null)
+ return r;
+ else // continue left
+ dir = -1;
}
else if ((pr = p.right) != null && h >= pr.hash)
s = pr;
@@ -840,12 +913,12 @@ public class ConcurrentHashMapV8
pp = (dir > 0) ? p.right : p.left;
}
- TreeNode f = first;
- TreeNode x = first = new TreeNode(h, k, v, f, p);
+ TreeNode f = first;
+ TreeNode x = first = new TreeNode(h, k, v, f, p);
if (p == null)
root = x;
else { // attach and rebalance; adapted from CLR
- TreeNode xp, xpp;
+ TreeNode xp, xpp;
if (f != null)
f.prev = x;
if (dir <= 0)
@@ -855,9 +928,9 @@ public class ConcurrentHashMapV8
x.red = true;
while (x != null && (xp = x.parent) != null && xp.red &&
(xpp = xp.parent) != null) {
- TreeNode xppl = xpp.left;
+ TreeNode xppl = xpp.left;
if (xp == xppl) {
- TreeNode y = xpp.right;
+ TreeNode y = xpp.right;
if (y != null && y.red) {
y.red = false;
xp.red = false;
@@ -879,7 +952,7 @@ public class ConcurrentHashMapV8
}
}
else {
- TreeNode y = xppl;
+ TreeNode y = xppl;
if (y != null && y.red) {
y.red = false;
xp.red = false;
@@ -901,7 +974,7 @@ public class ConcurrentHashMapV8
}
}
}
- TreeNode r = root;
+ TreeNode r = root;
if (r != null && r.red)
r.red = false;
}
@@ -916,31 +989,31 @@ public class ConcurrentHashMapV8
* that are accessible independently of lock. So instead we
* swap the tree linkages.
*/
- final void deleteTreeNode(TreeNode p) {
- TreeNode next = (TreeNode)p.next; // unlink traversal pointers
- TreeNode pred = p.prev;
+ final void deleteTreeNode(TreeNode p) {
+ TreeNode next = (TreeNode)p.next; // unlink traversal pointers
+ TreeNode pred = p.prev;
if (pred == null)
first = next;
else
pred.next = next;
if (next != null)
next.prev = pred;
- TreeNode replacement;
- TreeNode pl = p.left;
- TreeNode pr = p.right;
+ TreeNode replacement;
+ TreeNode pl = p.left;
+ TreeNode pr = p.right;
if (pl != null && pr != null) {
- TreeNode s = pr, sl;
+ TreeNode s = pr, sl;
while ((sl = s.left) != null) // find successor
s = sl;
boolean c = s.red; s.red = p.red; p.red = c; // swap colors
- TreeNode sr = s.right;
- TreeNode pp = p.parent;
+ TreeNode sr = s.right;
+ TreeNode pp = p.parent;
if (s == pr) { // p was s's direct parent
p.parent = s;
s.right = p;
}
else {
- TreeNode sp = s.parent;
+ TreeNode sp = s.parent;
if ((p.parent = sp) != null) {
if (s == sp.left)
sp.left = p;
@@ -965,7 +1038,7 @@ public class ConcurrentHashMapV8
}
else
replacement = (pl != null) ? pl : pr;
- TreeNode pp = p.parent;
+ TreeNode pp = p.parent;
if (replacement == null) {
if (pp == null) {
root = null;
@@ -984,15 +1057,15 @@ public class ConcurrentHashMapV8
p.left = p.right = p.parent = null;
}
if (!p.red) { // rebalance, from CLR
- TreeNode x = replacement;
+ TreeNode x = replacement;
while (x != null) {
- TreeNode xp, xpl;
+ TreeNode xp, xpl;
if (x.red || (xp = x.parent) == null) {
x.red = false;
break;
}
if (x == (xpl = xp.left)) {
- TreeNode sib = xp.right;
+ TreeNode sib = xp.right;
if (sib != null && sib.red) {
sib.red = false;
xp.red = true;
@@ -1002,7 +1075,7 @@ public class ConcurrentHashMapV8
if (sib == null)
x = xp;
else {
- TreeNode sl = sib.left, sr = sib.right;
+ TreeNode sl = sib.left, sr = sib.right;
if ((sr == null || !sr.red) &&
(sl == null || !sl.red)) {
sib.red = true;
@@ -1014,7 +1087,8 @@ public class ConcurrentHashMapV8
sl.red = false;
sib.red = true;
rotateRight(sib);
- sib = (xp = x.parent) == null ? null : xp.right;
+ sib = (xp = x.parent) == null ?
+ null : xp.right;
}
if (sib != null) {
sib.red = (xp == null) ? false : xp.red;
@@ -1030,7 +1104,7 @@ public class ConcurrentHashMapV8
}
}
else { // symmetric
- TreeNode sib = xpl;
+ TreeNode sib = xpl;
if (sib != null && sib.red) {
sib.red = false;
xp.red = true;
@@ -1040,7 +1114,7 @@ public class ConcurrentHashMapV8
if (sib == null)
x = xp;
else {
- TreeNode sl = sib.left, sr = sib.right;
+ TreeNode sl = sib.left, sr = sib.right;
if ((sl == null || !sl.red) &&
(sr == null || !sr.red)) {
sib.red = true;
@@ -1052,7 +1126,8 @@ public class ConcurrentHashMapV8
sr.red = false;
sib.red = true;
rotateLeft(sib);
- sib = (xp = x.parent) == null ? null : xp.left;
+ sib = (xp = x.parent) == null ?
+ null : xp.left;
}
if (sib != null) {
sib.red = (xp == null) ? false : xp.red;
@@ -1082,7 +1157,7 @@ public class ConcurrentHashMapV8
/* ---------------- Collision reduction methods -------------- */
/**
- * Spreads higher bits to lower, and also forces top 2 bits to 0.
+ * Spreads higher bits to lower, and also forces top bit to 0.
* Because the table uses power-of-two masking, sets of hashes
* that vary only in bits above the current mask will always
* collide. (Among known examples are sets of Float keys holding
@@ -1100,37 +1175,35 @@ public class ConcurrentHashMapV8
}
/**
- * Replaces a list bin with a tree bin. Call only when locked.
- * Fails to replace if the given key is non-comparable or table
- * is, or needs, resizing.
- */
- private final void replaceWithTreeBin(Node[] tab, int index, Object key) {
- if ((key instanceof Comparable) &&
- (tab.length >= MAXIMUM_CAPACITY || counter.sum() < (long)sizeCtl)) {
- TreeBin t = new TreeBin();
- for (Node e = tabAt(tab, index); e != null; e = e.next)
- t.putTreeNode(e.hash & HASH_BITS, e.key, e.val);
- setTabAt(tab, index, new Node(MOVED, t, null, null));
+ * Replaces a list bin with a tree bin if key is comparable. Call
+ * only when locked.
+ */
+ private final void replaceWithTreeBin(Node[] tab, int index, Object key) {
+ if (key instanceof Comparable) {
+ TreeBin t = new TreeBin();
+ for (Node e = tabAt(tab, index); e != null; e = e.next)
+ t.putTreeNode(e.hash, e.key, e.val);
+ setTabAt(tab, index, new Node(MOVED, t, null, null));
}
}
/* ---------------- Internal access and update methods -------------- */
/** Implementation for get and containsKey */
- private final Object internalGet(Object k) {
+ @SuppressWarnings("unchecked") private final V internalGet(Object k) {
int h = spread(k.hashCode());
- retry: for (Node[] tab = table; tab != null;) {
- Node e, p; Object ek, ev; int eh; // locals to read fields once
+ retry: for (Node[] tab = table; tab != null;) {
+ Node e; Object ek; V ev; int eh; // locals to read fields once
for (e = tabAt(tab, (tab.length - 1) & h); e != null; e = e.next) {
- if ((eh = e.hash) == MOVED) {
+ if ((eh = e.hash) < 0) {
if ((ek = e.key) instanceof TreeBin) // search TreeBin
- return ((TreeBin)ek).getValue(h, k);
- else { // restart with new table
- tab = (Node[])ek;
+ return ((TreeBin)ek).getValue(h, k);
+ else { // restart with new table
+ tab = (Node[])ek;
continue retry;
}
}
- else if ((eh & HASH_BITS) == h && (ev = e.val) != null &&
+ else if (eh == h && (ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek)))
return ev;
}
@@ -1144,26 +1217,27 @@ public class ConcurrentHashMapV8
* Replaces node value with v, conditional upon match of cv if
* non-null. If resulting value is null, delete.
*/
- private final Object internalReplace(Object k, Object v, Object cv) {
+ @SuppressWarnings("unchecked") private final V internalReplace
+ (Object k, V v, Object cv) {
int h = spread(k.hashCode());
- Object oldVal = null;
- for (Node[] tab = table;;) {
- Node f; int i, fh; Object fk;
+ V oldVal = null;
+ for (Node[] tab = table;;) {
+ Node f; int i, fh; Object fk;
if (tab == null ||
(f = tabAt(tab, i = (tab.length - 1) & h)) == null)
break;
- else if ((fh = f.hash) == MOVED) {
+ else if ((fh = f.hash) < 0) {
if ((fk = f.key) instanceof TreeBin) {
- TreeBin t = (TreeBin)fk;
+ TreeBin t = (TreeBin)fk;
boolean validated = false;
boolean deleted = false;
t.acquire(0);
try {
if (tabAt(tab, i) == f) {
validated = true;
- TreeNode p = t.getTreeNode(h, k, t.root);
+ TreeNode p = t.getTreeNode(h, k, t.root);
if (p != null) {
- Object pv = p.val;
+ V pv = p.val;
if (cv == null || cv == pv || cv.equals(pv)) {
oldVal = pv;
if ((p.val = v) == null) {
@@ -1178,35 +1252,31 @@ public class ConcurrentHashMapV8
}
if (validated) {
if (deleted)
- counter.add(-1L);
+ addCount(-1L, -1);
break;
}
}
else
- tab = (Node[])fk;
+ tab = (Node[])fk;
}
- else if ((fh & HASH_BITS) != h && f.next == null) // precheck
+ else if (fh != h && f.next == null) // precheck
break; // rules out possible existence
- else if ((fh & LOCKED) != 0) {
- checkForResize(); // try resizing if can't get lock
- f.tryAwaitLock(tab, i);
- }
- else if (f.casHash(fh, fh | LOCKED)) {
+ else {
boolean validated = false;
boolean deleted = false;
- try {
+ synchronized (f) {
if (tabAt(tab, i) == f) {
validated = true;
- for (Node e = f, pred = null;;) {
- Object ek, ev;
- if ((e.hash & HASH_BITS) == h &&
+ for (Node e = f, pred = null;;) {
+ Object ek; V ev;
+ if (e.hash == h &&
((ev = e.val) != null) &&
((ek = e.key) == k || k.equals(ek))) {
if (cv == null || cv == ev || cv.equals(ev)) {
oldVal = ev;
if ((e.val = v) == null) {
deleted = true;
- Node en = e.next;
+ Node en = e.next;
if (pred != null)
pred.next = en;
else
@@ -1220,15 +1290,10 @@ public class ConcurrentHashMapV8
break;
}
}
- } finally {
- if (!f.casHash(fh | LOCKED, fh)) {
- f.hash = fh;
- synchronized (f) { f.notifyAll(); };
- }
}
if (validated) {
if (deleted)
- counter.add(-1L);
+ addCount(-1L, -1);
break;
}
}
@@ -1237,393 +1302,353 @@ public class ConcurrentHashMapV8
}
/*
- * Internal versions of the five insertion methods, each a
- * little more complicated than the last. All have
- * the same basic structure as the first (internalPut):
+ * Internal versions of insertion methods
+ * All have the same basic structure as the first (internalPut):
* 1. If table uninitialized, create
* 2. If bin empty, try to CAS new node
* 3. If bin stale, use new table
* 4. if bin converted to TreeBin, validate and relay to TreeBin methods
* 5. Lock and validate; if valid, scan and add or update
*
- * The others interweave other checks and/or alternative actions:
- * * Plain put checks for and performs resize after insertion.
- * * putIfAbsent prescans for mapping without lock (and fails to add
- * if present), which also makes pre-emptive resize checks worthwhile.
- * * computeIfAbsent extends form used in putIfAbsent with additional
- * mechanics to deal with, calls, potential exceptions and null
- * returns from function call.
- * * compute uses the same function-call mechanics, but without
- * the prescans
- * * putAll attempts to pre-allocate enough table space
- * and more lazily performs count updates and checks.
- *
- * Someday when details settle down a bit more, it might be worth
- * some factoring to reduce sprawl.
+ * The putAll method differs mainly in attempting to pre-allocate
+ * enough table space, and also more lazily performs count updates
+ * and checks.
+ *
+ * Most of the function-accepting methods can't be factored nicely
+ * because they require different functional forms, so instead
+ * sprawl out similar mechanics.
*/
- /** Implementation for put */
- private final Object internalPut(Object k, Object v) {
+ /** Implementation for put and putIfAbsent */
+ @SuppressWarnings("unchecked") private final V internalPut
+ (K k, V v, boolean onlyIfAbsent) {
+ if (k == null || v == null) throw new NullPointerException();
int h = spread(k.hashCode());
- int count = 0;
- for (Node[] tab = table;;) {
- int i; Node f; int fh; Object fk;
+ int len = 0;
+ for (Node[] tab = table;;) {
+ int i, fh; Node f; Object fk; V fv;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
- if (casTabAt(tab, i, null, new Node(h, k, v, null)))
+ if (casTabAt(tab, i, null, new Node(h, k, v, null)))
break; // no lock when adding to empty bin
}
- else if ((fh = f.hash) == MOVED) {
+ else if ((fh = f.hash) < 0) {
if ((fk = f.key) instanceof TreeBin) {
- TreeBin t = (TreeBin)fk;
- Object oldVal = null;
+ TreeBin t = (TreeBin)fk;
+ V oldVal = null;
t.acquire(0);
try {
if (tabAt(tab, i) == f) {
- count = 2;
- TreeNode p = t.putTreeNode(h, k, v);
+ len = 2;
+ TreeNode p = t.putTreeNode(h, k, v);
if (p != null) {
oldVal = p.val;
- p.val = v;
+ if (!onlyIfAbsent)
+ p.val = v;
}
}
} finally {
t.release(0);
}
- if (count != 0) {
+ if (len != 0) {
if (oldVal != null)
return oldVal;
break;
}
}
else
- tab = (Node[])fk;
+ tab = (Node[])fk;
}
- else if ((fh & LOCKED) != 0) {
- checkForResize();
- f.tryAwaitLock(tab, i);
- }
- else if (f.casHash(fh, fh | LOCKED)) {
- Object oldVal = null;
- try { // needed in case equals() throws
+ else if (onlyIfAbsent && fh == h && (fv = f.val) != null &&
+ ((fk = f.key) == k || k.equals(fk))) // peek while nearby
+ return fv;
+ else {
+ V oldVal = null;
+ synchronized (f) {
if (tabAt(tab, i) == f) {
- count = 1;
- for (Node e = f;; ++count) {
- Object ek, ev;
- if ((e.hash & HASH_BITS) == h &&
+ len = 1;
+ for (Node e = f;; ++len) {
+ Object ek; V ev;
+ if (e.hash == h &&
(ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek))) {
oldVal = ev;
- e.val = v;
+ if (!onlyIfAbsent)
+ e.val = v;
break;
}
- Node last = e;
+ Node last = e;
if ((e = e.next) == null) {
- last.next = new Node(h, k, v, null);
- if (count >= TREE_THRESHOLD)
+ last.next = new Node(h, k, v, null);
+ if (len >= TREE_THRESHOLD)
replaceWithTreeBin(tab, i, k);
break;
}
}
}
- } finally { // unlock and signal if needed
- if (!f.casHash(fh | LOCKED, fh)) {
- f.hash = fh;
- synchronized (f) { f.notifyAll(); };
- }
}
- if (count != 0) {
+ if (len != 0) {
if (oldVal != null)
return oldVal;
- if (tab.length <= 64)
- count = 2;
break;
}
}
}
- counter.add(1L);
- if (count > 1)
- checkForResize();
+ addCount(1L, len);
return null;
}
- /** Implementation for putIfAbsent */
- private final Object internalPutIfAbsent(Object k, Object v) {
+ /** Implementation for computeIfAbsent */
+ @SuppressWarnings("unchecked") private final V internalComputeIfAbsent
+ (K k, Fun mf) {
+ if (k == null || mf == null)
+ throw new NullPointerException();
int h = spread(k.hashCode());
- int count = 0;
- for (Node[] tab = table;;) {
- int i; Node f; int fh; Object fk, fv;
+ V val = null;
+ int len = 0;
+ for (Node[] tab = table;;) {
+ Node f; int i; Object fk;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
- if (casTabAt(tab, i, null, new Node(h, k, v, null)))
+ Node node = new Node(h, k, null, null);
+ synchronized (node) {
+ if (casTabAt(tab, i, null, node)) {
+ len = 1;
+ try {
+ if ((val = mf.apply(k)) != null)
+ node.val = val;
+ } finally {
+ if (val == null)
+ setTabAt(tab, i, null);
+ }
+ }
+ }
+ if (len != 0)
break;
}
- else if ((fh = f.hash) == MOVED) {
+ else if (f.hash < 0) {
if ((fk = f.key) instanceof TreeBin) {
- TreeBin t = (TreeBin)fk;
- Object oldVal = null;
+ TreeBin t = (TreeBin)fk;
+ boolean added = false;
t.acquire(0);
try {
if (tabAt(tab, i) == f) {
- count = 2;
- TreeNode p = t.putTreeNode(h, k, v);
+ len = 1;
+ TreeNode p = t.getTreeNode(h, k, t.root);
if (p != null)
- oldVal = p.val;
+ val = p.val;
+ else if ((val = mf.apply(k)) != null) {
+ added = true;
+ len = 2;
+ t.putTreeNode(h, k, val);
+ }
}
} finally {
t.release(0);
}
- if (count != 0) {
- if (oldVal != null)
- return oldVal;
+ if (len != 0) {
+ if (!added)
+ return val;
break;
}
}
else
- tab = (Node[])fk;
+ tab = (Node[])fk;
}
- else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
- ((fk = f.key) == k || k.equals(fk)))
- return fv;
else {
- Node g = f.next;
- if (g != null) { // at least 2 nodes -- search and maybe resize
- for (Node e = g;;) {
- Object ek, ev;
- if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
- ((ek = e.key) == k || k.equals(ek)))
- return ev;
- if ((e = e.next) == null) {
- checkForResize();
- break;
- }
- }
+ for (Node e = f; e != null; e = e.next) { // prescan
+ Object ek; V ev;
+ if (e.hash == h && (ev = e.val) != null &&
+ ((ek = e.key) == k || k.equals(ek)))
+ return ev;
}
- if (((fh = f.hash) & LOCKED) != 0) {
- checkForResize();
- f.tryAwaitLock(tab, i);
- }
- else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
- Object oldVal = null;
- try {
- if (tabAt(tab, i) == f) {
- count = 1;
- for (Node e = f;; ++count) {
- Object ek, ev;
- if ((e.hash & HASH_BITS) == h &&
- (ev = e.val) != null &&
- ((ek = e.key) == k || k.equals(ek))) {
- oldVal = ev;
- break;
- }
- Node last = e;
- if ((e = e.next) == null) {
- last.next = new Node(h, k, v, null);
- if (count >= TREE_THRESHOLD)
+ boolean added = false;
+ synchronized (f) {
+ if (tabAt(tab, i) == f) {
+ len = 1;
+ for (Node e = f;; ++len) {
+ Object ek; V ev;
+ if (e.hash == h &&
+ (ev = e.val) != null &&
+ ((ek = e.key) == k || k.equals(ek))) {
+ val = ev;
+ break;
+ }
+ Node last = e;
+ if ((e = e.next) == null) {
+ if ((val = mf.apply(k)) != null) {
+ added = true;
+ last.next = new Node(h, k, val, null);
+ if (len >= TREE_THRESHOLD)
replaceWithTreeBin(tab, i, k);
- break;
}
+ break;
}
}
- } finally {
- if (!f.casHash(fh | LOCKED, fh)) {
- f.hash = fh;
- synchronized (f) { f.notifyAll(); };
- }
- }
- if (count != 0) {
- if (oldVal != null)
- return oldVal;
- if (tab.length <= 64)
- count = 2;
- break;
}
}
+ if (len != 0) {
+ if (!added)
+ return val;
+ break;
+ }
}
}
- counter.add(1L);
- if (count > 1)
- checkForResize();
- return null;
+ if (val != null)
+ addCount(1L, len);
+ return val;
}
- /** Implementation for computeIfAbsent */
- private final Object internalComputeIfAbsent(K k,
- MappingFunction mf) {
+ /** Implementation for compute */
+ @SuppressWarnings("unchecked") private final V internalCompute
+ (K k, boolean onlyIfPresent,
+ BiFun mf) {
+ if (k == null || mf == null)
+ throw new NullPointerException();
int h = spread(k.hashCode());
- Object val = null;
- int count = 0;
- for (Node[] tab = table;;) {
- Node f; int i, fh; Object fk, fv;
+ V val = null;
+ int delta = 0;
+ int len = 0;
+ for (Node[] tab = table;;) {
+ Node f; int i, fh; Object fk;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
- Node node = new Node(fh = h | LOCKED, k, null, null);
- if (casTabAt(tab, i, null, node)) {
- count = 1;
- try {
- if ((val = mf.map(k)) != null)
- node.val = val;
- } finally {
- if (val == null)
- setTabAt(tab, i, null);
- if (!node.casHash(fh, h)) {
- node.hash = h;
- synchronized (node) { node.notifyAll(); };
+ if (onlyIfPresent)
+ break;
+ Node node = new Node(h, k, null, null);
+ synchronized (node) {
+ if (casTabAt(tab, i, null, node)) {
+ try {
+ len = 1;
+ if ((val = mf.apply(k, null)) != null) {
+ node.val = val;
+ delta = 1;
+ }
+ } finally {
+ if (delta == 0)
+ setTabAt(tab, i, null);
}
}
}
- if (count != 0)
+ if (len != 0)
break;
}
- else if ((fh = f.hash) == MOVED) {
+ else if ((fh = f.hash) < 0) {
if ((fk = f.key) instanceof TreeBin) {
- TreeBin t = (TreeBin)fk;
- boolean added = false;
+ TreeBin t = (TreeBin)fk;
t.acquire(0);
try {
if (tabAt(tab, i) == f) {
- count = 1;
- TreeNode p = t.getTreeNode(h, k, t.root);
- if (p != null)
- val = p.val;
- else if ((val = mf.map(k)) != null) {
- added = true;
- count = 2;
- t.putTreeNode(h, k, val);
+ len = 1;
+ TreeNode p = t.getTreeNode(h, k, t.root);
+ if (p == null && onlyIfPresent)
+ break;
+ V pv = (p == null) ? null : p.val;
+ if ((val = mf.apply(k, pv)) != null) {
+ if (p != null)
+ p.val = val;
+ else {
+ len = 2;
+ delta = 1;
+ t.putTreeNode(h, k, val);
+ }
+ }
+ else if (p != null) {
+ delta = -1;
+ t.deleteTreeNode(p);
}
}
} finally {
t.release(0);
}
- if (count != 0) {
- if (!added)
- return val;
+ if (len != 0)
break;
- }
}
else
- tab = (Node[])fk;
+ tab = (Node[])fk;
}
- else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
- ((fk = f.key) == k || k.equals(fk)))
- return fv;
else {
- Node g = f.next;
- if (g != null) {
- for (Node e = g;;) {
- Object ek, ev;
- if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
- ((ek = e.key) == k || k.equals(ek)))
- return ev;
- if ((e = e.next) == null) {
- checkForResize();
- break;
- }
- }
- }
- if (((fh = f.hash) & LOCKED) != 0) {
- checkForResize();
- f.tryAwaitLock(tab, i);
- }
- else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
- boolean added = false;
- try {
- if (tabAt(tab, i) == f) {
- count = 1;
- for (Node e = f;; ++count) {
- Object ek, ev;
- if ((e.hash & HASH_BITS) == h &&
- (ev = e.val) != null &&
- ((ek = e.key) == k || k.equals(ek))) {
- val = ev;
- break;
+ synchronized (f) {
+ if (tabAt(tab, i) == f) {
+ len = 1;
+ for (Node e = f, pred = null;; ++len) {
+ Object ek; V ev;
+ if (e.hash == h &&
+ (ev = e.val) != null &&
+ ((ek = e.key) == k || k.equals(ek))) {
+ val = mf.apply(k, ev);
+ if (val != null)
+ e.val = val;
+ else {
+ delta = -1;
+ Node en = e.next;
+ if (pred != null)
+ pred.next = en;
+ else
+ setTabAt(tab, i, en);
}
- Node last = e;
- if ((e = e.next) == null) {
- if ((val = mf.map(k)) != null) {
- added = true;
- last.next = new Node(h, k, val, null);
- if (count >= TREE_THRESHOLD)
- replaceWithTreeBin(tab, i, k);
- }
- break;
+ break;
+ }
+ pred = e;
+ if ((e = e.next) == null) {
+ if (!onlyIfPresent &&
+ (val = mf.apply(k, null)) != null) {
+ pred.next = new Node(h, k, val, null);
+ delta = 1;
+ if (len >= TREE_THRESHOLD)
+ replaceWithTreeBin(tab, i, k);
}
+ break;
}
}
- } finally {
- if (!f.casHash(fh | LOCKED, fh)) {
- f.hash = fh;
- synchronized (f) { f.notifyAll(); };
- }
- }
- if (count != 0) {
- if (!added)
- return val;
- if (tab.length <= 64)
- count = 2;
- break;
}
}
+ if (len != 0)
+ break;
}
}
- if (val != null) {
- counter.add(1L);
- if (count > 1)
- checkForResize();
- }
+ if (delta != 0)
+ addCount((long)delta, len);
return val;
}
- /** Implementation for compute */
- @SuppressWarnings("unchecked")
- private final Object internalCompute(K k,
- RemappingFunction mf) {
+ /** Implementation for merge */
+ @SuppressWarnings("unchecked") private final V internalMerge
+ (K k, V v, BiFun mf) {
+ if (k == null || v == null || mf == null)
+ throw new NullPointerException();
int h = spread(k.hashCode());
- Object val = null;
+ V val = null;
int delta = 0;
- int count = 0;
- for (Node[] tab = table;;) {
- Node f; int i, fh; Object fk;
+ int len = 0;
+ for (Node[] tab = table;;) {
+ int i; Node f; Object fk; V fv;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
- Node node = new Node(fh = h | LOCKED, k, null, null);
- if (casTabAt(tab, i, null, node)) {
- try {
- count = 1;
- if ((val = mf.remap(k, null)) != null) {
- node.val = val;
- delta = 1;
- }
- } finally {
- if (delta == 0)
- setTabAt(tab, i, null);
- if (!node.casHash(fh, h)) {
- node.hash = h;
- synchronized (node) { node.notifyAll(); };
- }
- }
- }
- if (count != 0)
+ if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
+ delta = 1;
+ val = v;
break;
+ }
}
- else if ((fh = f.hash) == MOVED) {
+ else if (f.hash < 0) {
if ((fk = f.key) instanceof TreeBin) {
- TreeBin t = (TreeBin)fk;
+ TreeBin t = (TreeBin)fk;
t.acquire(0);
try {
if (tabAt(tab, i) == f) {
- count = 1;
- TreeNode p = t.getTreeNode(h, k, t.root);
- Object pv = (p == null) ? null : p.val;
- if ((val = mf.remap(k, (V)pv)) != null) {
+ len = 1;
+ TreeNode p = t.getTreeNode(h, k, t.root);
+ val = (p == null) ? v : mf.apply(p.val, v);
+ if (val != null) {
if (p != null)
p.val = val;
else {
- count = 2;
+ len = 2;
delta = 1;
t.putTreeNode(h, k, val);
}
@@ -1636,31 +1661,27 @@ public class ConcurrentHashMapV8
} finally {
t.release(0);
}
- if (count != 0)
+ if (len != 0)
break;
}
else
- tab = (Node[])fk;
+ tab = (Node[])fk;
}
- else if ((fh & LOCKED) != 0) {
- checkForResize();
- f.tryAwaitLock(tab, i);
- }
- else if (f.casHash(fh, fh | LOCKED)) {
- try {
+ else {
+ synchronized (f) {
if (tabAt(tab, i) == f) {
- count = 1;
- for (Node e = f, pred = null;; ++count) {
- Object ek, ev;
- if ((e.hash & HASH_BITS) == h &&
+ len = 1;
+ for (Node e = f, pred = null;; ++len) {
+ Object ek; V ev;
+ if (e.hash == h &&
(ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek))) {
- val = mf.remap(k, (V)ev);
+ val = mf.apply(ev, v);
if (val != null)
e.val = val;
else {
delta = -1;
- Node en = e.next;
+ Node en = e.next;
if (pred != null)
pred.next = en;
else
@@ -1670,70 +1691,59 @@ public class ConcurrentHashMapV8
}
pred = e;
if ((e = e.next) == null) {
- if ((val = mf.remap(k, null)) != null) {
- pred.next = new Node(h, k, val, null);
- delta = 1;
- if (count >= TREE_THRESHOLD)
- replaceWithTreeBin(tab, i, k);
- }
+ val = v;
+ pred.next = new Node(h, k, val, null);
+ delta = 1;
+ if (len >= TREE_THRESHOLD)
+ replaceWithTreeBin(tab, i, k);
break;
}
}
}
- } finally {
- if (!f.casHash(fh | LOCKED, fh)) {
- f.hash = fh;
- synchronized (f) { f.notifyAll(); };
- }
}
- if (count != 0) {
- if (tab.length <= 64)
- count = 2;
+ if (len != 0)
break;
- }
}
}
- if (delta != 0) {
- counter.add((long)delta);
- if (count > 1)
- checkForResize();
- }
+ if (delta != 0)
+ addCount((long)delta, len);
return val;
}
/** Implementation for putAll */
- private final void internalPutAll(Map m) {
+ @SuppressWarnings("unchecked") private final void internalPutAll
+ (Map m) {
tryPresize(m.size());
long delta = 0L; // number of uncommitted additions
boolean npe = false; // to throw exception on exit for nulls
try { // to clean up counts on other exceptions
- for (Map.Entry entry : m.entrySet()) {
- Object k, v;
+ for (Map.Entry entry : m.entrySet()) {
+ Object k; V v;
if (entry == null || (k = entry.getKey()) == null ||
(v = entry.getValue()) == null) {
npe = true;
break;
}
int h = spread(k.hashCode());
- for (Node[] tab = table;;) {
- int i; Node f; int fh; Object fk;
+ for (Node[] tab = table;;) {
+ int i; Node f; int fh; Object fk;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null){
- if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
+ if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
++delta;
break;
}
}
- else if ((fh = f.hash) == MOVED) {
+ else if ((fh = f.hash) < 0) {
if ((fk = f.key) instanceof TreeBin) {
- TreeBin t = (TreeBin)fk;
+ TreeBin t = (TreeBin)fk;
boolean validated = false;
t.acquire(0);
try {
if (tabAt(tab, i) == f) {
validated = true;
- TreeNode p = t.getTreeNode(h, k, t.root);
+ TreeNode p = t.getTreeNode(h, k, t.root);
if (p != null)
p.val = v;
else {
@@ -1748,48 +1758,36 @@ public class ConcurrentHashMapV8
break;
}
else
- tab = (Node[])fk;
+ tab = (Node[])fk;
}
- else if ((fh & LOCKED) != 0) {
- counter.add(delta);
- delta = 0L;
- checkForResize();
- f.tryAwaitLock(tab, i);
- }
- else if (f.casHash(fh, fh | LOCKED)) {
- int count = 0;
- try {
+ else {
+ int len = 0;
+ synchronized (f) {
if (tabAt(tab, i) == f) {
- count = 1;
- for (Node e = f;; ++count) {
- Object ek, ev;
- if ((e.hash & HASH_BITS) == h &&
+ len = 1;
+ for (Node e = f;; ++len) {
+ Object ek; V ev;
+ if (e.hash == h &&
(ev = e.val) != null &&
((ek = e.key) == k || k.equals(ek))) {
e.val = v;
break;
}
- Node last = e;
+ Node last = e;
if ((e = e.next) == null) {
++delta;
- last.next = new Node(h, k, v, null);
- if (count >= TREE_THRESHOLD)
+ last.next = new Node(h, k, v, null);
+ if (len >= TREE_THRESHOLD)
replaceWithTreeBin(tab, i, k);
break;
}
}
}
- } finally {
- if (!f.casHash(fh | LOCKED, fh)) {
- f.hash = fh;
- synchronized (f) { f.notifyAll(); };
- }
}
- if (count != 0) {
- if (count > 1) {
- counter.add(delta);
+ if (len != 0) {
+ if (len > 1) {
+ addCount(delta, len);
delta = 0L;
- checkForResize();
}
break;
}
@@ -1797,13 +1795,68 @@ public class ConcurrentHashMapV8
}
}
} finally {
- if (delta != 0)
- counter.add(delta);
+ if (delta != 0L)
+ addCount(delta, 2);
}
if (npe)
throw new NullPointerException();
}
+ /**
+ * Implementation for clear. Steps through each bin, removing all
+ * nodes.
+ */
+ @SuppressWarnings("unchecked") private final void internalClear() {
+ long delta = 0L; // negative number of deletions
+ int i = 0;
+ Node[] tab = table;
+ while (tab != null && i < tab.length) {
+ Node f = tabAt(tab, i);
+ if (f == null)
+ ++i;
+ else if (f.hash < 0) {
+ Object fk;
+ if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ t.acquire(0);
+ try {
+ if (tabAt(tab, i) == f) {
+ for (Node p = t.first; p != null; p = p.next) {
+ if (p.val != null) { // (currently always true)
+ p.val = null;
+ --delta;
+ }
+ }
+ t.first = null;
+ t.root = null;
+ ++i;
+ }
+ } finally {
+ t.release(0);
+ }
+ }
+ else
+ tab = (Node[])fk;
+ }
+ else {
+ synchronized (f) {
+ if (tabAt(tab, i) == f) {
+ for (Node e = f; e != null; e = e.next) {
+ if (e.val != null) { // (currently always true)
+ e.val = null;
+ --delta;
+ }
+ }
+ setTabAt(tab, i, null);
+ ++i;
+ }
+ }
+ }
+ }
+ if (delta != 0L)
+ addCount(delta, -1);
+ }
+
/* ---------------- Table Initialization and Resizing -------------- */
/**
@@ -1823,16 +1876,17 @@ public class ConcurrentHashMapV8
/**
* Initializes table, using the size recorded in sizeCtl.
*/
- private final Node[] initTable() {
- Node[] tab; int sc;
+ @SuppressWarnings("unchecked") private final Node[] initTable() {
+ Node[] tab; int sc;
while ((tab = table) == null) {
if ((sc = sizeCtl) < 0)
Thread.yield(); // lost initialization race; just spin
- else if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
+ else if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) {
try {
if ((tab = table) == null) {
int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
- tab = table = new Node[n];
+ @SuppressWarnings("rawtypes") Node[] tb = new Node[n];
+ table = tab = (Node[])tb;
sc = n - (n >>> 2);
}
} finally {
@@ -1845,24 +1899,47 @@ public class ConcurrentHashMapV8
}
/**
- * If table is too small and not already resizing, creates next
- * table and transfers bins. Rechecks occupancy after a transfer
- * to see if another resize is already needed because resizings
- * are lagging additions.
- */
- private final void checkForResize() {
- Node[] tab; int n, sc;
- while ((tab = table) != null &&
- (n = tab.length) < MAXIMUM_CAPACITY &&
- (sc = sizeCtl) >= 0 && counter.sum() >= (long)sc &&
- UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
- try {
- if (tab == table) {
- table = rebuild(tab);
- sc = (n << 1) - (n >>> 1);
+ * Adds to count, and if table is too small and not already
+ * resizing, initiates transfer. If already resizing, helps
+ * perform transfer if work is available. Rechecks occupancy
+ * after a transfer to see if another resize is already needed
+ * because resizings are lagging additions.
+ *
+ * @param x the count to add
+ * @param check if <0, don't check resize, if <= 1 only check if uncontended
+ */
+ private final void addCount(long x, int check) {
+ CounterCell[] as; long b, s;
+ if ((as = counterCells) != null ||
+ !U.compareAndSwapLong(this, BASECOUNT, b = baseCount, s = b + x)) {
+ CounterHashCode hc; CounterCell a; long v; int m;
+ boolean uncontended = true;
+ if ((hc = threadCounterHashCode.get()) == null ||
+ as == null || (m = as.length - 1) < 0 ||
+ (a = as[m & hc.code]) == null ||
+ !(uncontended =
+ U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x))) {
+ fullAddCount(x, hc, uncontended);
+ return;
+ }
+ if (check <= 1)
+ return;
+ s = sumCount();
+ }
+ if (check >= 0) {
+ Node[] tab, nt; int sc;
+ while (s >= (long)(sc = sizeCtl) && (tab = table) != null &&
+ tab.length < MAXIMUM_CAPACITY) {
+ if (sc < 0) {
+ if (sc == -1 || transferIndex <= transferOrigin ||
+ (nt = nextTable) == null)
+ break;
+ if (U.compareAndSwapInt(this, SIZECTL, sc, sc - 1))
+ transfer(tab, nt);
}
- } finally {
- sizeCtl = sc;
+ else if (U.compareAndSwapInt(this, SIZECTL, sc, -2))
+ transfer(tab, null);
+ s = sumCount();
}
}
}
@@ -1872,18 +1949,19 @@ public class ConcurrentHashMapV8
*
* @param size number of elements (doesn't need to be perfectly accurate)
*/
- private final void tryPresize(int size) {
+ @SuppressWarnings("unchecked") private final void tryPresize(int size) {
int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
tableSizeFor(size + (size >>> 1) + 1);
int sc;
while ((sc = sizeCtl) >= 0) {
- Node[] tab = table; int n;
+ Node[] tab = table; int n;
if (tab == null || (n = tab.length) == 0) {
n = (sc > c) ? sc : c;
- if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
+ if (U.compareAndSwapInt(this, SIZECTL, sc, -1)) {
try {
if (table == tab) {
- table = new Node[n];
+ @SuppressWarnings("rawtypes") Node[] tb = new Node[n];
+ table = (Node[])tb;
sc = n - (n >>> 2);
}
} finally {
@@ -1893,260 +1971,270 @@ public class ConcurrentHashMapV8
}
else if (c <= sc || n >= MAXIMUM_CAPACITY)
break;
- else if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
- try {
- if (table == tab) {
- table = rebuild(tab);
- sc = (n << 1) - (n >>> 1);
- }
- } finally {
- sizeCtl = sc;
- }
- }
+ else if (tab == table &&
+ U.compareAndSwapInt(this, SIZECTL, sc, -2))
+ transfer(tab, null);
}
}
- /*
+ /**
* Moves and/or copies the nodes in each bin to new table. See
* above for explanation.
- *
- * @return the new table
*/
- private static final Node[] rebuild(Node[] tab) {
- int n = tab.length;
- Node[] nextTab = new Node[n << 1];
- Node fwd = new Node(MOVED, nextTab, null, null);
- int[] buffer = null; // holds bins to revisit; null until needed
- Node rev = null; // reverse forwarder; null until needed
- int nbuffered = 0; // the number of bins in buffer list
- int bufferIndex = 0; // buffer index of current buffered bin
- int bin = n - 1; // current non-buffered bin or -1 if none
-
- for (int i = bin;;) { // start upwards sweep
- int fh; Node f;
- if ((f = tabAt(tab, i)) == null) {
- if (bin >= 0) { // no lock needed (or available)
- if (!casTabAt(tab, i, f, fwd))
- continue;
- }
- else { // transiently use a locked forwarding node
- Node g = new Node(MOVED|LOCKED, nextTab, null, null);
- if (!casTabAt(tab, i, f, g))
- continue;
+ @SuppressWarnings("unchecked") private final void transfer
+ (Node[] tab, Node[] nextTab) {
+ int n = tab.length, stride;
+ if ((stride = (NCPU > 1) ? (n >>> 3) / NCPU : n) < MIN_TRANSFER_STRIDE)
+ stride = MIN_TRANSFER_STRIDE; // subdivide range
+ if (nextTab == null) { // initiating
+ try {
+ @SuppressWarnings("rawtypes") Node[] tb = new Node[n << 1];
+ nextTab = (Node[])tb;
+ } catch (Throwable ex) { // try to cope with OOME
+ sizeCtl = Integer.MAX_VALUE;
+ return;
+ }
+ nextTable = nextTab;
+ transferOrigin = n;
+ transferIndex = n;
+ Node rev = new Node(MOVED, tab, null, null);
+ for (int k = n; k > 0;) { // progressively reveal ready slots
+ int nextk = (k > stride) ? k - stride : 0;
+ for (int m = nextk; m < k; ++m)
+ nextTab[m] = rev;
+ for (int m = n + nextk; m < n + k; ++m)
+ nextTab[m] = rev;
+ U.putOrderedInt(this, TRANSFERORIGIN, k = nextk);
+ }
+ }
+ int nextn = nextTab.length;
+ Node fwd = new Node(MOVED, nextTab, null, null);
+ boolean advance = true;
+ for (int i = 0, bound = 0;;) {
+ int nextIndex, nextBound; Node f; Object fk;
+ while (advance) {
+ if (--i >= bound)
+ advance = false;
+ else if ((nextIndex = transferIndex) <= transferOrigin) {
+ i = -1;
+ advance = false;
+ }
+ else if (U.compareAndSwapInt
+ (this, TRANSFERINDEX, nextIndex,
+ nextBound = (nextIndex > stride ?
+ nextIndex - stride : 0))) {
+ bound = nextBound;
+ i = nextIndex - 1;
+ advance = false;
+ }
+ }
+ if (i < 0 || i >= n || i + n >= nextn) {
+ for (int sc;;) {
+ if (U.compareAndSwapInt(this, SIZECTL, sc = sizeCtl, ++sc)) {
+ if (sc == -1) {
+ nextTable = null;
+ table = nextTab;
+ sizeCtl = (n << 1) - (n >>> 1);
+ }
+ return;
+ }
+ }
+ }
+ else if ((f = tabAt(tab, i)) == null) {
+ if (casTabAt(tab, i, null, fwd)) {
setTabAt(nextTab, i, null);
setTabAt(nextTab, i + n, null);
- setTabAt(tab, i, fwd);
- if (!g.casHash(MOVED|LOCKED, MOVED)) {
- g.hash = MOVED;
- synchronized (g) { g.notifyAll(); }
- }
+ advance = true;
}
}
- else if ((fh = f.hash) == MOVED) {
- Object fk = f.key;
- if (fk instanceof TreeBin) {
- TreeBin t = (TreeBin)fk;
- boolean validated = false;
- t.acquire(0);
- try {
- if (tabAt(tab, i) == f) {
- validated = true;
- splitTreeBin(nextTab, i, t);
- setTabAt(tab, i, fwd);
+ else if (f.hash >= 0) {
+ synchronized (f) {
+ if (tabAt(tab, i) == f) {
+ int runBit = f.hash & n;
+ Node lastRun = f, lo = null, hi = null;
+ for (Node p = f.next; p != null; p = p.next) {
+ int b = p.hash & n;
+ if (b != runBit) {
+ runBit = b;
+ lastRun = p;
+ }
}
- } finally {
- t.release(0);
+ if (runBit == 0)
+ lo = lastRun;
+ else
+ hi = lastRun;
+ for (Node p = f; p != lastRun; p = p.next) {
+ int ph = p.hash;
+ Object pk = p.key; V pv = p.val;
+ if ((ph & n) == 0)
+ lo = new Node(ph, pk, pv, lo);
+ else
+ hi = new Node(ph, pk, pv, hi);
+ }
+ setTabAt(nextTab, i, lo);
+ setTabAt(nextTab, i + n, hi);
+ setTabAt(tab, i, fwd);
+ advance = true;
}
- if (!validated)
- continue;
}
}
- else if ((fh & LOCKED) == 0 && f.casHash(fh, fh|LOCKED)) {
- boolean validated = false;
- try { // split to lo and hi lists; copying as needed
+ else if ((fk = f.key) instanceof TreeBin) {
+ TreeBin t = (TreeBin)fk;
+ t.acquire(0);
+ try {
if (tabAt(tab, i) == f) {
- validated = true;
- splitBin(nextTab, i, f);
+ TreeBin lt = new TreeBin();
+ TreeBin ht = new TreeBin();
+ int lc = 0, hc = 0;
+ for (Node e = t.first; e != null; e = e.next) {
+ int h = e.hash;
+ Object k = e.key; V v = e.val;
+ if ((h & n) == 0) {
+ ++lc;
+ lt.putTreeNode(h, k, v);
+ }
+ else {
+ ++hc;
+ ht.putTreeNode(h, k, v);
+ }
+ }
+ Node ln, hn; // throw away trees if too small
+ if (lc < TREE_THRESHOLD) {
+ ln = null;
+ for (Node p = lt.first; p != null; p = p.next)
+ ln = new Node(p.hash, p.key, p.val, ln);
+ }
+ else
+ ln = new Node(MOVED, lt, null, null);
+ setTabAt(nextTab, i, ln);
+ if (hc < TREE_THRESHOLD) {
+ hn = null;
+ for (Node p = ht.first; p != null; p = p.next)
+ hn = new Node