* 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
@@ -287,7 +285,6 @@ public class ConcurrentHashMapV8
Spliterator split();
}
-
/*
* Overview:
*
@@ -298,17 +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
@@ -322,19 +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
@@ -343,12 +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
@@ -410,43 +394,43 @@ 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 Iter) 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 Traverser constructor)
@@ -461,20 +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
@@ -525,27 +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 -------------- */
@@ -553,22 +578,50 @@ 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 counter maintaining number of elements.
+ * The next table to use; non-null only while resizing.
*/
- private transient final LongAdder counter;
+ private transient volatile Node[] nextTable;
+
+ /**
+ * Base counter value, used mainly when there is no contention,
+ * but also as a fallback during table initialization
+ * races. Updated via CAS.
+ */
+ 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 KeySetView keySet;
private transient ValuesView values;
@@ -591,16 +644,19 @@ public class ConcurrentHashMapV8
* inline assignments below.
*/
- static final Node tabAt(Node[] tab, int i) { // used by Iter
- 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 -------------- */
@@ -615,88 +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.
- *
- * The initial sanity check on tab and bounds is not currently
- * necessary in the only usages of this method, but enables
- * use in other future contexts.
- */
- final void tryAwaitLock(Node[] tab, int i) {
- if (tab != null && i >= 0 && i < tab.length) { // sanity 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 -------------- */
@@ -704,14 +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;
}
@@ -760,10 +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; }
@@ -794,9 +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)
@@ -811,9 +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)
@@ -831,8 +817,8 @@ public class ConcurrentHashMapV8
* Returns the TreeNode (or null if not found) for the given key
* starting at given root.
*/
- @SuppressWarnings("unchecked") 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;
@@ -842,16 +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
@@ -866,10 +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);
@@ -878,7 +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;
}
@@ -892,10 +879,10 @@ public class ConcurrentHashMapV8
* Finds or adds a node.
* @return null if added
*/
- @SuppressWarnings("unchecked") 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;
@@ -906,11 +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;
@@ -923,12 +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)
@@ -938,9 +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;
@@ -962,7 +952,7 @@ public class ConcurrentHashMapV8
}
}
else {
- TreeNode y = xppl;
+ TreeNode y = xppl;
if (y != null && y.red) {
y.red = false;
xp.red = false;
@@ -984,7 +974,7 @@ public class ConcurrentHashMapV8
}
}
}
- TreeNode r = root;
+ TreeNode r = root;
if (r != null && r.red)
r.red = false;
}
@@ -999,31 +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;
@@ -1048,7 +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;
@@ -1067,15 +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;
@@ -1085,7 +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;
@@ -1097,7 +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;
@@ -1113,7 +1104,7 @@ public class ConcurrentHashMapV8
}
}
else { // symmetric
- TreeNode sib = xpl;
+ TreeNode sib = xpl;
if (sib != null && sib.red) {
sib.red = false;
xp.red = true;
@@ -1123,7 +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;
@@ -1135,7 +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;
@@ -1165,7 +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
@@ -1183,37 +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;
}
@@ -1227,26 +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) {
@@ -1261,35 +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
@@ -1303,15 +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;
}
}
@@ -1320,396 +1302,256 @@ public class ConcurrentHashMapV8
}
/*
- * Internal versions of the six 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
- * * merge acts as putIfAbsent in the absent case, but invokes the
- * update function if present
- * * 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();
- return null;
- }
-
- /** Implementation for putIfAbsent */
- private final Object internalPutIfAbsent(Object k, Object v) {
- int h = spread(k.hashCode());
- int count = 0;
- for (Node[] tab = table;;) {
- int i; Node f; int fh; Object fk, 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)))
break;
- }
- else if ((fh = f.hash) == MOVED) {
- if ((fk = f.key) instanceof TreeBin) {
- TreeBin t = (TreeBin)fk;
- Object oldVal = null;
- t.acquire(0);
- try {
- if (tabAt(tab, i) == f) {
- count = 2;
- TreeNode p = t.putTreeNode(h, k, v);
- if (p != null)
- oldVal = p.val;
- }
- } finally {
- t.release(0);
- }
- if (count != 0) {
- if (oldVal != null)
- return oldVal;
- break;
- }
- }
- else
- 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;
- }
- }
- }
- 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)
- replaceWithTreeBin(tab, i, k);
- 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;
- }
}
}
}
- counter.add(1L);
- if (count > 1)
- checkForResize();
+ addCount(1L, len);
return null;
}
/** Implementation for computeIfAbsent */
- private final Object internalComputeIfAbsent(K k,
- Fun mf) {
+ @SuppressWarnings("unchecked") private final V internalComputeIfAbsent
+ (K k, Fun 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 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) {
- Node node = new Node(fh = h | LOCKED, k, null, null);
- if (casTabAt(tab, i, null, node)) {
- count = 1;
- try {
- if ((val = mf.apply(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(); };
+ 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 (count != 0)
+ 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;
+ TreeBin t = (TreeBin)fk;
boolean added = false;
t.acquire(0);
try {
if (tabAt(tab, i) == f) {
- count = 1;
- TreeNode p = t.getTreeNode(h, k, t.root);
+ len = 1;
+ TreeNode p = t.getTreeNode(h, k, t.root);
if (p != null)
val = p.val;
else if ((val = mf.apply(k)) != null) {
added = true;
- count = 2;
+ len = 2;
t.putTreeNode(h, k, val);
}
}
} finally {
t.release(0);
}
- if (count != 0) {
+ 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) {
- 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);
+ 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;
}
- 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;
- }
- 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 (count >= TREE_THRESHOLD)
- replaceWithTreeBin(tab, i, k);
- }
- break;
+ 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;
}
}
- } 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) {
+ if (!added)
+ return val;
+ break;
+ }
}
}
- if (val != null) {
- counter.add(1L);
- if (count > 1)
- checkForResize();
- }
+ if (val != null)
+ addCount(1L, len);
return val;
}
/** Implementation for compute */
- @SuppressWarnings("unchecked") private final Object internalCompute
- (K k, boolean onlyIfPresent, BiFun mf) {
+ @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;
+ 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;;) {
+ Node f; int i, fh; Object fk;
if (tab == null)
tab = initTable();
else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
if (onlyIfPresent)
break;
- Node node = new Node(fh = h | LOCKED, k, null, null);
- if (casTabAt(tab, i, null, node)) {
- try {
- count = 1;
- if ((val = mf.apply(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(); };
+ 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;
+ 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.apply(k, (V)pv)) != null) {
+ 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 {
- count = 2;
+ len = 2;
delta = 1;
t.putTreeNode(h, k, val);
}
@@ -1722,31 +1564,27 @@ public class ConcurrentHashMapV8
} finally {
t.release(0);
}
- if (count != 0)
+ if (len != 0)
break;
}
else
- tab = (Node[])fk;
- }
- else if ((fh & LOCKED) != 0) {
- checkForResize();
- f.tryAwaitLock(tab, i);
+ tab = (Node[])fk;
}
- 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.apply(k, (V)ev);
+ val = mf.apply(k, ev);
if (val != null)
e.val = val;
else {
delta = -1;
- Node en = e.next;
+ Node en = e.next;
if (pred != null)
pred.next = en;
else
@@ -1756,69 +1594,61 @@ public class ConcurrentHashMapV8
}
pred = e;
if ((e = e.next) == null) {
- if (!onlyIfPresent && (val = mf.apply(k, null)) != null) {
- pred.next = new Node(h, k, val, null);
+ if (!onlyIfPresent &&
+ (val = mf.apply(k, null)) != null) {
+ pred.next = new Node(h, k, val, null);
delta = 1;
- if (count >= TREE_THRESHOLD)
+ 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 merge */
- @SuppressWarnings("unchecked") private final Object internalMerge
+ @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;;) {
- int i; Node f; int fh; Object fk, fv;
+ 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) {
- if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
+ 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);
- val = (p == null) ? v : mf.apply((V)p.val, v);
+ 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);
}
@@ -1831,31 +1661,27 @@ public class ConcurrentHashMapV8
} finally {
t.release(0);
}
- if (count != 0)
+ if (len != 0)
break;
}
else
- tab = (Node[])fk;
- }
- else if ((fh & LOCKED) != 0) {
- checkForResize();
- f.tryAwaitLock(tab, i);
+ tab = (Node[])fk;
}
- 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.apply(v, (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
@@ -1866,68 +1692,58 @@ public class ConcurrentHashMapV8
pred = e;
if ((e = e.next) == null) {
val = v;
- pred.next = new Node(h, k, val, null);
+ pred.next = new Node(h, k, val, null);
delta = 1;
- if (count >= TREE_THRESHOLD)
+ 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 {
@@ -1942,48 +1758,36 @@ public class ConcurrentHashMapV8
break;
}
else
- tab = (Node[])fk;
- }
- else if ((fh & LOCKED) != 0) {
- counter.add(delta);
- delta = 0L;
- checkForResize();
- f.tryAwaitLock(tab, i);
+ tab = (Node[])fk;
}
- 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;
}
@@ -1991,13 +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 -------------- */
/**
@@ -2017,16 +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 {
@@ -2039,24 +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();
}
}
}
@@ -2066,18 +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 {
@@ -2087,257 +1971,263 @@ 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) { // Unbuffered; 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(p.hash, p.key, p.val, hn);
+ }
+ else
+ hn = new Node(MOVED, ht, null, null);
+ setTabAt(nextTab, i + n, hn);
setTabAt(tab, i, fwd);
+ advance = true;
}
} finally {
- if (!f.casHash(fh | LOCKED, fh)) {
- f.hash = fh;
- synchronized (f) { f.notifyAll(); };
- }
+ t.release(0);
}
- if (!validated)
- continue;
- }
- else {
- if (buffer == null) // initialize buffer for revisits
- buffer = new int[TRANSFER_BUFFER_SIZE];
- if (bin < 0 && bufferIndex > 0) {
- int j = buffer[--bufferIndex];
- buffer[bufferIndex] = i;
- i = j; // swap with another bin
- continue;
- }
- if (bin < 0 || nbuffered >= TRANSFER_BUFFER_SIZE) {
- f.tryAwaitLock(tab, i);
- continue; // no other options -- block
- }
- if (rev == null) // initialize reverse-forwarder
- rev = new Node(MOVED, tab, null, null);
- if (tabAt(tab, i) != f || (f.hash & LOCKED) == 0)
- continue; // recheck before adding to list
- buffer[nbuffered++] = i;
- setTabAt(nextTab, i, rev); // install place-holders
- setTabAt(nextTab, i + n, rev);
- }
-
- if (bin > 0)
- i = --bin;
- else if (buffer != null && nbuffered > 0) {
- bin = -1;
- i = buffer[bufferIndex = --nbuffered];
}
else
- return nextTab;
+ advance = true; // already processed
}
}
- /**
- * Splits a normal bin with list headed by e into lo and hi parts;
- * installs in given table.
- */
- private static void splitBin(Node[] nextTab, int i, Node e) {
- int bit = nextTab.length >>> 1; // bit to split on
- int runBit = e.hash & bit;
- Node lastRun = e, lo = null, hi = null;
- for (Node p = e.next; p != null; p = p.next) {
- int b = p.hash & bit;
- if (b != runBit) {
- runBit = b;
- lastRun = p;
+ /* ---------------- Counter support -------------- */
+
+ final long sumCount() {
+ CounterCell[] as = counterCells; CounterCell a;
+ long sum = baseCount;
+ if (as != null) {
+ for (int i = 0; i < as.length; ++i) {
+ if ((a = as[i]) != null)
+ sum += a.value;
}
}
- if (runBit == 0)
- lo = lastRun;
- else
- hi = lastRun;
- for (Node p = e; p != lastRun; p = p.next) {
- int ph = p.hash & HASH_BITS;
- Object pk = p.key, pv = p.val;
- if ((ph & bit) == 0)
- lo = new Node(ph, pk, pv, lo);
- else
- hi = new Node(ph, pk, pv, hi);
- }
- setTabAt(nextTab, i, lo);
- setTabAt(nextTab, i + bit, hi);
+ return sum;
}
- /**
- * Splits a tree bin into lo and hi parts; installs in given table.
- */
- private static void splitTreeBin(Node[] nextTab, int i, TreeBin t) {
- int bit = nextTab.length >>> 1;
- 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 & HASH_BITS;
- Object k = e.key, v = e.val;
- if ((h & bit) == 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 >>> 1)) {
- 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 >>> 1)) {
- hn = null;
- for (Node p = ht.first; p != null; p = p.next)
- hn = new Node(p.hash, p.key, p.val, hn);
+ // See LongAdder version for explanation
+ private final void fullAddCount(long x, CounterHashCode hc,
+ boolean wasUncontended) {
+ int h;
+ if (hc == null) {
+ hc = new CounterHashCode();
+ int s = counterHashCodeGenerator.addAndGet(SEED_INCREMENT);
+ h = hc.code = (s == 0) ? 1 : s; // Avoid zero
+ threadCounterHashCode.set(hc);
}
else
- hn = new Node(MOVED, ht, null, null);
- setTabAt(nextTab, i + bit, hn);
- }
-
- /**
- * Implementation for clear. Steps through each bin, removing all
- * nodes.
- */
- private final void internalClear() {
- long delta = 0L; // negative number of deletions
- int i = 0;
- Node[] tab = table;
- while (tab != null && i < tab.length) {
- int fh; Object fk;
- Node f = tabAt(tab, i);
- if (f == null)
- ++i;
- else if ((fh = f.hash) == MOVED) {
- 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;
+ h = hc.code;
+ boolean collide = false; // True if last slot nonempty
+ for (;;) {
+ CounterCell[] as; CounterCell a; int n; long v;
+ if ((as = counterCells) != null && (n = as.length) > 0) {
+ if ((a = as[(n - 1) & h]) == null) {
+ if (counterBusy == 0) { // Try to attach new Cell
+ CounterCell r = new CounterCell(x); // Optimistic create
+ if (counterBusy == 0 &&
+ U.compareAndSwapInt(this, COUNTERBUSY, 0, 1)) {
+ boolean created = false;
+ try { // Recheck under lock
+ CounterCell[] rs; int m, j;
+ if ((rs = counterCells) != null &&
+ (m = rs.length) > 0 &&
+ rs[j = (m - 1) & h] == null) {
+ rs[j] = r;
+ created = true;
}
+ } finally {
+ counterBusy = 0;
}
- t.first = null;
- t.root = null;
- ++i;
+ if (created)
+ break;
+ continue; // Slot is now non-empty
}
- } finally {
- t.release(0);
}
+ collide = false;
}
- else
- tab = (Node[])fk;
- }
- else if ((fh & LOCKED) != 0) {
- counter.add(delta); // opportunistically update count
- delta = 0L;
- f.tryAwaitLock(tab, i);
- }
- else if (f.casHash(fh, fh | LOCKED)) {
- try {
- 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;
- }
+ else if (!wasUncontended) // CAS already known to fail
+ wasUncontended = true; // Continue after rehash
+ else if (U.compareAndSwapLong(a, CELLVALUE, v = a.value, v + x))
+ break;
+ else if (counterCells != as || n >= NCPU)
+ collide = false; // At max size or stale
+ else if (!collide)
+ collide = true;
+ else if (counterBusy == 0 &&
+ U.compareAndSwapInt(this, COUNTERBUSY, 0, 1)) {
+ try {
+ if (counterCells == as) {// Expand table unless stale
+ CounterCell[] rs = new CounterCell[n << 1];
+ for (int i = 0; i < n; ++i)
+ rs[i] = as[i];
+ counterCells = rs;
}
- setTabAt(tab, i, null);
- ++i;
+ } finally {
+ counterBusy = 0;
}
- } finally {
- if (!f.casHash(fh | LOCKED, fh)) {
- f.hash = fh;
- synchronized (f) { f.notifyAll(); };
+ collide = false;
+ continue; // Retry with expanded table
+ }
+ h ^= h << 13; // Rehash
+ h ^= h >>> 17;
+ h ^= h << 5;
+ }
+ else if (counterBusy == 0 && counterCells == as &&
+ U.compareAndSwapInt(this, COUNTERBUSY, 0, 1)) {
+ boolean init = false;
+ try { // Initialize table
+ if (counterCells == as) {
+ CounterCell[] rs = new CounterCell[2];
+ rs[h & 1] = new CounterCell(x);
+ counterCells = rs;
+ init = true;
}
+ } finally {
+ counterBusy = 0;
}
+ if (init)
+ break;
}
+ else if (U.compareAndSwapLong(this, BASECOUNT, v = baseCount, v + x))
+ break; // Fall back on using base
}
- if (delta != 0)
- counter.add(delta);
+ hc.code = h; // Record index for next time
}
/* ----------------Table Traversal -------------- */
@@ -2380,56 +2270,61 @@ public class ConcurrentHashMapV8
* across threads, iteration terminates if a bounds checks fails
* for a table read.
*
- * This class extends ForkJoinTask to streamline parallel
- * iteration in bulk operations (see BulkTask). This adds only an
- * int of space overhead, which is close enough to negligible in
- * cases where it is not needed to not worry about it. Because
- * ForkJoinTask is Serializable, but iterators need not be, we
- * need to add warning suppressions.
+ * This class extends CountedCompleter to streamline parallel
+ * iteration in bulk operations. This adds only a few fields of
+ * space overhead, which is small enough in cases where it is not
+ * needed to not worry about it. Because CountedCompleter is
+ * Serializable, but iterators need not be, we need to add warning
+ * suppressions.
*/
- @SuppressWarnings("serial") static class Traverser extends ForkJoinTask {
+ @SuppressWarnings("serial") static class Traverser
+ extends CountedCompleter {
final ConcurrentHashMapV8 map;
- Node next; // the next entry to use
+ Node next; // the next entry to use
Object nextKey; // cached key field of next
- Object nextVal; // cached val field of next
- Node[] tab; // current table; updated if resized
+ V nextVal; // cached val field of next
+ Node[] tab; // current table; updated if resized
int index; // index of bin to use next
int baseIndex; // current index of initial table
int baseLimit; // index bound for initial table
int baseSize; // initial table size
+ int batch; // split control
/** Creates iterator for all entries in the table. */
Traverser(ConcurrentHashMapV8 map) {
this.map = map;
}
- /** Creates iterator for split() methods */
- Traverser(Traverser it) {
- ConcurrentHashMapV8 m; Node[] t;
- if ((m = this.map = it.map) == null)
- t = null;
- else if ((t = it.tab) == null && // force parent tab initialization
- (t = it.tab = m.table) != null)
- it.baseLimit = it.baseSize = t.length;
- this.tab = t;
- this.baseSize = it.baseSize;
- it.baseLimit = this.index = this.baseIndex =
- ((this.baseLimit = it.baseLimit) + it.baseIndex + 1) >>> 1;
+ /** Creates iterator for split() methods and task constructors */
+ Traverser(ConcurrentHashMapV8 map, Traverser it, int batch) {
+ super(it);
+ this.batch = batch;
+ if ((this.map = map) != null && it != null) { // split parent
+ Node[] t;
+ if ((t = it.tab) == null &&
+ (t = it.tab = map.table) != null)
+ it.baseLimit = it.baseSize = t.length;
+ this.tab = t;
+ this.baseSize = it.baseSize;
+ int hi = this.baseLimit = it.baseLimit;
+ it.baseLimit = this.index = this.baseIndex =
+ (hi + it.baseIndex + 1) >>> 1;
+ }
}
/**
* Advances next; returns nextVal or null if terminated.
* See above for explanation.
*/
- final Object advance() {
- Node e = next;
- Object ev = null;
+ @SuppressWarnings("unchecked") final V advance() {
+ Node e = next;
+ V ev = null;
outer: do {
if (e != null) // advance past used/skipped node
e = e.next;
while (e == null) { // get to next non-null bin
ConcurrentHashMapV8 m;
- Node[] t; int b, i, n; Object ek; // checks must use locals
+ Node