changeset 48274:bf476235671a

8192943: Optimize atomic accumulators using VarHandle getAndSet Reviewed-by: martin, psandoz, chegar
author dl
date Fri, 08 Dec 2017 15:26:56 -0800
parents 8a6970acf8ad
children dd5157f363ab
files src/java.base/share/classes/java/util/concurrent/atomic/DoubleAccumulator.java src/java.base/share/classes/java/util/concurrent/atomic/DoubleAdder.java src/java.base/share/classes/java/util/concurrent/atomic/LongAccumulator.java src/java.base/share/classes/java/util/concurrent/atomic/LongAdder.java src/java.base/share/classes/java/util/concurrent/atomic/Striped64.java
diffstat 5 files changed, 113 insertions(+), 117 deletions(-) [+]
line wrap: on
line diff
--- a/src/java.base/share/classes/java/util/concurrent/atomic/DoubleAccumulator.java	Fri Dec 08 15:22:58 2017 -0800
+++ b/src/java.base/share/classes/java/util/concurrent/atomic/DoubleAccumulator.java	Fri Dec 08 15:26:56 2017 -0800
@@ -105,20 +105,20 @@
      * @param x the value
      */
     public void accumulate(double x) {
-        Cell[] as; long b, v, r; int m; Cell a;
-        if ((as = cells) != null
+        Cell[] cs; long b, v, r; int m; Cell c;
+        if ((cs = cells) != null
             || ((r = doubleToRawLongBits
                 (function.applyAsDouble(longBitsToDouble(b = base), x))) != b
                 && !casBase(b, r))) {
             boolean uncontended = true;
-            if (as == null
-                || (m = as.length - 1) < 0
-                || (a = as[getProbe() & m]) == null
+            if (cs == null
+                || (m = cs.length - 1) < 0
+                || (c = cs[getProbe() & m]) == null
                 || !(uncontended =
                      ((r = doubleToRawLongBits
                        (function.applyAsDouble
-                        (longBitsToDouble(v = a.value), x))) == v)
-                     || a.cas(v, r)))
+                        (longBitsToDouble(v = c.value), x))) == v)
+                     || c.cas(v, r)))
                 doubleAccumulate(x, function, uncontended);
         }
     }
@@ -133,13 +133,13 @@
      * @return the current value
      */
     public double get() {
-        Cell[] as = cells;
+        Cell[] cs = cells;
         double result = longBitsToDouble(base);
-        if (as != null) {
-            for (Cell a : as)
-                if (a != null)
+        if (cs != null) {
+            for (Cell c : cs)
+                if (c != null)
                     result = function.applyAsDouble
-                        (result, longBitsToDouble(a.value));
+                        (result, longBitsToDouble(c.value));
         }
         return result;
     }
@@ -153,12 +153,12 @@
      * updating.
      */
     public void reset() {
-        Cell[] as = cells;
+        Cell[] cs = cells;
         base = identity;
-        if (as != null) {
-            for (Cell a : as)
-                if (a != null)
-                    a.reset(identity);
+        if (cs != null) {
+            for (Cell c : cs)
+                if (c != null)
+                    c.reset(identity);
         }
     }
 
@@ -173,14 +173,12 @@
      * @return the value before reset
      */
     public double getThenReset() {
-        Cell[] as = cells;
-        double result = longBitsToDouble(base);
-        base = identity;
-        if (as != null) {
-            for (Cell a : as) {
-                if (a != null) {
-                    double v = longBitsToDouble(a.value);
-                    a.reset(identity);
+        Cell[] cs = cells;
+        double result = longBitsToDouble(getAndSetBase(identity));
+        if (cs != null) {
+            for (Cell c : cs) {
+                if (c != null) {
+                    double v = longBitsToDouble(c.getAndSet(identity));
                     result = function.applyAsDouble(result, v);
                 }
             }
--- a/src/java.base/share/classes/java/util/concurrent/atomic/DoubleAdder.java	Fri Dec 08 15:22:58 2017 -0800
+++ b/src/java.base/share/classes/java/util/concurrent/atomic/DoubleAdder.java	Fri Dec 08 15:26:56 2017 -0800
@@ -87,15 +87,15 @@
      * @param x the value to add
      */
     public void add(double x) {
-        Cell[] as; long b, v; int m; Cell a;
-        if ((as = cells) != null ||
+        Cell[] cs; long b, v; int m; Cell c;
+        if ((cs = cells) != null ||
             !casBase(b = base,
                      Double.doubleToRawLongBits
                      (Double.longBitsToDouble(b) + x))) {
             boolean uncontended = true;
-            if (as == null || (m = as.length - 1) < 0 ||
-                (a = as[getProbe() & m]) == null ||
-                !(uncontended = a.cas(v = a.value,
+            if (cs == null || (m = cs.length - 1) < 0 ||
+                (c = cs[getProbe() & m]) == null ||
+                !(uncontended = c.cas(v = c.value,
                                       Double.doubleToRawLongBits
                                       (Double.longBitsToDouble(v) + x))))
                 doubleAccumulate(x, null, uncontended);
@@ -115,12 +115,12 @@
      * @return the sum
      */
     public double sum() {
-        Cell[] as = cells;
+        Cell[] cs = cells;
         double sum = Double.longBitsToDouble(base);
-        if (as != null) {
-            for (Cell a : as)
-                if (a != null)
-                    sum += Double.longBitsToDouble(a.value);
+        if (cs != null) {
+            for (Cell c : cs)
+                if (c != null)
+                    sum += Double.longBitsToDouble(c.value);
         }
         return sum;
     }
@@ -133,12 +133,12 @@
      * known that no threads are concurrently updating.
      */
     public void reset() {
-        Cell[] as = cells;
+        Cell[] cs = cells;
         base = 0L; // relies on fact that double 0 must have same rep as long
-        if (as != null) {
-            for (Cell a : as)
-                if (a != null)
-                    a.reset();
+        if (cs != null) {
+            for (Cell c : cs)
+                if (c != null)
+                    c.reset();
         }
     }
 
@@ -153,16 +153,12 @@
      * @return the sum
      */
     public double sumThenReset() {
-        Cell[] as = cells;
-        double sum = Double.longBitsToDouble(base);
-        base = 0L;
-        if (as != null) {
-            for (Cell a : as) {
-                if (a != null) {
-                    long v = a.value;
-                    a.reset();
-                    sum += Double.longBitsToDouble(v);
-                }
+        Cell[] cs = cells;
+        double sum = Double.longBitsToDouble(getAndSetBase(0L));
+        if (cs != null) {
+            for (Cell c : cs) {
+                if (c != null)
+                    sum += Double.longBitsToDouble(c.getAndSet(0L));
             }
         }
         return sum;
--- a/src/java.base/share/classes/java/util/concurrent/atomic/LongAccumulator.java	Fri Dec 08 15:22:58 2017 -0800
+++ b/src/java.base/share/classes/java/util/concurrent/atomic/LongAccumulator.java	Fri Dec 08 15:26:56 2017 -0800
@@ -103,17 +103,17 @@
      * @param x the value
      */
     public void accumulate(long x) {
-        Cell[] as; long b, v, r; int m; Cell a;
-        if ((as = cells) != null
+        Cell[] cs; long b, v, r; int m; Cell c;
+        if ((cs = cells) != null
             || ((r = function.applyAsLong(b = base, x)) != b
                 && !casBase(b, r))) {
             boolean uncontended = true;
-            if (as == null
-                || (m = as.length - 1) < 0
-                || (a = as[getProbe() & m]) == null
+            if (cs == null
+                || (m = cs.length - 1) < 0
+                || (c = cs[getProbe() & m]) == null
                 || !(uncontended =
-                     (r = function.applyAsLong(v = a.value, x)) == v
-                     || a.cas(v, r)))
+                     (r = function.applyAsLong(v = c.value, x)) == v
+                     || c.cas(v, r)))
                 longAccumulate(x, function, uncontended);
         }
     }
@@ -128,12 +128,12 @@
      * @return the current value
      */
     public long get() {
-        Cell[] as = cells;
+        Cell[] cs = cells;
         long result = base;
-        if (as != null) {
-            for (Cell a : as)
-                if (a != null)
-                    result = function.applyAsLong(result, a.value);
+        if (cs != null) {
+            for (Cell c : cs)
+                if (c != null)
+                    result = function.applyAsLong(result, c.value);
         }
         return result;
     }
@@ -147,12 +147,12 @@
      * updating.
      */
     public void reset() {
-        Cell[] as = cells;
+        Cell[] cs = cells;
         base = identity;
-        if (as != null) {
-            for (Cell a : as)
-                if (a != null)
-                    a.reset(identity);
+        if (cs != null) {
+            for (Cell c : cs)
+                if (c != null)
+                    c.reset(identity);
         }
     }
 
@@ -167,14 +167,12 @@
      * @return the value before reset
      */
     public long getThenReset() {
-        Cell[] as = cells;
-        long result = base;
-        base = identity;
-        if (as != null) {
-            for (Cell a : as) {
-                if (a != null) {
-                    long v = a.value;
-                    a.reset(identity);
+        Cell[] cs = cells;
+        long result = getAndSetBase(identity);
+        if (cs != null) {
+            for (Cell c : cs) {
+                if (c != null) {
+                    long v = c.getAndSet(identity);
                     result = function.applyAsLong(result, v);
                 }
             }
--- a/src/java.base/share/classes/java/util/concurrent/atomic/LongAdder.java	Fri Dec 08 15:22:58 2017 -0800
+++ b/src/java.base/share/classes/java/util/concurrent/atomic/LongAdder.java	Fri Dec 08 15:26:56 2017 -0800
@@ -83,12 +83,12 @@
      * @param x the value to add
      */
     public void add(long x) {
-        Cell[] as; long b, v; int m; Cell a;
-        if ((as = cells) != null || !casBase(b = base, b + x)) {
+        Cell[] cs; long b, v; int m; Cell c;
+        if ((cs = cells) != null || !casBase(b = base, b + x)) {
             boolean uncontended = true;
-            if (as == null || (m = as.length - 1) < 0 ||
-                (a = as[getProbe() & m]) == null ||
-                !(uncontended = a.cas(v = a.value, v + x)))
+            if (cs == null || (m = cs.length - 1) < 0 ||
+                (c = cs[getProbe() & m]) == null ||
+                !(uncontended = c.cas(v = c.value, v + x)))
                 longAccumulate(x, null, uncontended);
         }
     }
@@ -117,12 +117,12 @@
      * @return the sum
      */
     public long sum() {
-        Cell[] as = cells;
+        Cell[] cs = cells;
         long sum = base;
-        if (as != null) {
-            for (Cell a : as)
-                if (a != null)
-                    sum += a.value;
+        if (cs != null) {
+            for (Cell c : cs)
+                if (c != null)
+                    sum += c.value;
         }
         return sum;
     }
@@ -135,12 +135,12 @@
      * known that no threads are concurrently updating.
      */
     public void reset() {
-        Cell[] as = cells;
+        Cell[] cs = cells;
         base = 0L;
-        if (as != null) {
-            for (Cell a : as)
-                if (a != null)
-                    a.reset();
+        if (cs != null) {
+            for (Cell c : cs)
+                if (c != null)
+                    c.reset();
         }
     }
 
@@ -155,15 +155,12 @@
      * @return the sum
      */
     public long sumThenReset() {
-        Cell[] as = cells;
-        long sum = base;
-        base = 0L;
-        if (as != null) {
-            for (Cell a : as) {
-                if (a != null) {
-                    sum += a.value;
-                    a.reset();
-                }
+        Cell[] cs = cells;
+        long sum = getAndSetBase(0L);
+        if (cs != null) {
+            for (Cell c : cs) {
+                if (c != null)
+                    sum += c.getAndSet(0L);
             }
         }
         return sum;
--- a/src/java.base/share/classes/java/util/concurrent/atomic/Striped64.java	Fri Dec 08 15:22:58 2017 -0800
+++ b/src/java.base/share/classes/java/util/concurrent/atomic/Striped64.java	Fri Dec 08 15:26:56 2017 -0800
@@ -133,6 +133,9 @@
         final void reset(long identity) {
             VALUE.setVolatile(this, identity);
         }
+        final long getAndSet(long val) {
+            return (long)VALUE.getAndSet(this, val);
+        }
 
         // VarHandle mechanics
         private static final VarHandle VALUE;
@@ -178,6 +181,10 @@
         return BASE.compareAndSet(this, cmp, val);
     }
 
+    final long getAndSetBase(long val) {
+        return (long)BASE.getAndSet(this, val);
+    }
+
     /**
      * CASes the cellsBusy field from 0 to 1 to acquire lock.
      */
@@ -228,9 +235,9 @@
         }
         boolean collide = false;                // True if last slot nonempty
         done: for (;;) {
-            Cell[] as; Cell a; int n; long v;
-            if ((as = cells) != null && (n = as.length) > 0) {
-                if ((a = as[(n - 1) & h]) == null) {
+            Cell[] cs; Cell c; int n; long v;
+            if ((cs = cells) != null && (n = cs.length) > 0) {
+                if ((c = cs[(n - 1) & h]) == null) {
                     if (cellsBusy == 0) {       // Try to attach new Cell
                         Cell r = new Cell(x);   // Optimistically create
                         if (cellsBusy == 0 && casCellsBusy()) {
@@ -252,17 +259,17 @@
                 }
                 else if (!wasUncontended)       // CAS already known to fail
                     wasUncontended = true;      // Continue after rehash
-                else if (a.cas(v = a.value,
+                else if (c.cas(v = c.value,
                                (fn == null) ? v + x : fn.applyAsLong(v, x)))
                     break;
-                else if (n >= NCPU || cells != as)
+                else if (n >= NCPU || cells != cs)
                     collide = false;            // At max size or stale
                 else if (!collide)
                     collide = true;
                 else if (cellsBusy == 0 && casCellsBusy()) {
                     try {
-                        if (cells == as)        // Expand table unless stale
-                            cells = Arrays.copyOf(as, n << 1);
+                        if (cells == cs)        // Expand table unless stale
+                            cells = Arrays.copyOf(cs, n << 1);
                     } finally {
                         cellsBusy = 0;
                     }
@@ -271,9 +278,9 @@
                 }
                 h = advanceProbe(h);
             }
-            else if (cellsBusy == 0 && cells == as && casCellsBusy()) {
+            else if (cellsBusy == 0 && cells == cs && casCellsBusy()) {
                 try {                           // Initialize table
-                    if (cells == as) {
+                    if (cells == cs) {
                         Cell[] rs = new Cell[2];
                         rs[h & 1] = new Cell(x);
                         cells = rs;
@@ -312,9 +319,9 @@
         }
         boolean collide = false;                // True if last slot nonempty
         done: for (;;) {
-            Cell[] as; Cell a; int n; long v;
-            if ((as = cells) != null && (n = as.length) > 0) {
-                if ((a = as[(n - 1) & h]) == null) {
+            Cell[] cs; Cell c; int n; long v;
+            if ((cs = cells) != null && (n = cs.length) > 0) {
+                if ((c = cs[(n - 1) & h]) == null) {
                     if (cellsBusy == 0) {       // Try to attach new Cell
                         Cell r = new Cell(Double.doubleToRawLongBits(x));
                         if (cellsBusy == 0 && casCellsBusy()) {
@@ -336,16 +343,16 @@
                 }
                 else if (!wasUncontended)       // CAS already known to fail
                     wasUncontended = true;      // Continue after rehash
-                else if (a.cas(v = a.value, apply(fn, v, x)))
+                else if (c.cas(v = c.value, apply(fn, v, x)))
                     break;
-                else if (n >= NCPU || cells != as)
+                else if (n >= NCPU || cells != cs)
                     collide = false;            // At max size or stale
                 else if (!collide)
                     collide = true;
                 else if (cellsBusy == 0 && casCellsBusy()) {
                     try {
-                        if (cells == as)        // Expand table unless stale
-                            cells = Arrays.copyOf(as, n << 1);
+                        if (cells == cs)        // Expand table unless stale
+                            cells = Arrays.copyOf(cs, n << 1);
                     } finally {
                         cellsBusy = 0;
                     }
@@ -354,9 +361,9 @@
                 }
                 h = advanceProbe(h);
             }
-            else if (cellsBusy == 0 && cells == as && casCellsBusy()) {
+            else if (cellsBusy == 0 && cells == cs && casCellsBusy()) {
                 try {                           // Initialize table
-                    if (cells == as) {
+                    if (cells == cs) {
                         Cell[] rs = new Cell[2];
                         rs[h & 1] = new Cell(Double.doubleToRawLongBits(x));
                         cells = rs;