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From voze...@apache.org
Subject [5/9] ignite git commit: ignite-2333 : Fixed review remarks.
Date Tue, 01 Mar 2016 09:39:10 GMT
ignite-2333 : Fixed review remarks.


Project: http://git-wip-us.apache.org/repos/asf/ignite/repo
Commit: http://git-wip-us.apache.org/repos/asf/ignite/commit/13b3f4b9
Tree: http://git-wip-us.apache.org/repos/asf/ignite/tree/13b3f4b9
Diff: http://git-wip-us.apache.org/repos/asf/ignite/diff/13b3f4b9

Branch: refs/heads/ignite-2333
Commit: 13b3f4b961c2822cdfc70e1259d0f238d688ab57
Parents: f84d023
Author: Ilya Lantukh <ilantukh@gridgain.com>
Authored: Wed Feb 24 11:42:15 2016 +0300
Committer: Ilya Lantukh <ilantukh@gridgain.com>
Committed: Wed Feb 24 11:42:15 2016 +0300

----------------------------------------------------------------------
 .../util/StripedCompositeReadWriteLock.java     | 149 ++++++++++++++++---
 1 file changed, 130 insertions(+), 19 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/ignite/blob/13b3f4b9/modules/core/src/main/java/org/apache/ignite/internal/util/StripedCompositeReadWriteLock.java
----------------------------------------------------------------------
diff --git a/modules/core/src/main/java/org/apache/ignite/internal/util/StripedCompositeReadWriteLock.java
b/modules/core/src/main/java/org/apache/ignite/internal/util/StripedCompositeReadWriteLock.java
index ae95f6c..1a8ce2e 100644
--- a/modules/core/src/main/java/org/apache/ignite/internal/util/StripedCompositeReadWriteLock.java
+++ b/modules/core/src/main/java/org/apache/ignite/internal/util/StripedCompositeReadWriteLock.java
@@ -1,54 +1,140 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package org.apache.ignite.internal.util;
 
 import org.jetbrains.annotations.NotNull;
 
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 /**
- * @author Ilya Lantukh
+ * ReadWriteLock with striping mechanics.
+ * Compared to {@link ReentrantReadWriteLock} it has slightly improved performance of {@link
ReadWriteLock#readLock()}
+ * operations at the cost of {@link ReadWriteLock#writeLock()} operations and memory consumption.
+ * It also supports reentrancy semantics like {@link ReentrantReadWriteLock}.
  */
 public class StripedCompositeReadWriteLock implements ReadWriteLock {
 
-    private final PaddedReentrantReadWriteLock[] locks;
+    /**
+     * Locks.
+     */
+    private final ReentrantReadWriteLock[] locks;
 
+    /**
+     * Composite write lock.
+     */
     private final CompositeWriteLock compositeWriteLock;
 
-    public StripedCompositeReadWriteLock(int concurrencyLevel) {
-        locks = new PaddedReentrantReadWriteLock[concurrencyLevel];
-
-        for (int i = 0; i < concurrencyLevel; i++)
+    /**
+     * Atomic field updated for {@link #counter}.
+     */
+    private static final AtomicIntegerFieldUpdater<StripedCompositeReadWriteLock> COUNTER_UPD
=
+        AtomicIntegerFieldUpdater.newUpdater(StripedCompositeReadWriteLock.class, "counter");
+
+    /**
+     * Counter of {@link #readLock()} calls.
+     */
+    @SuppressWarnings("UnusedDeclaration")
+    private volatile int counter = 0;
+
+    /**
+     * Creates a new instance with given concurrency level.
+     *
+     * @param concurrencyLvl Number of internal read locks.
+     */
+    public StripedCompositeReadWriteLock(int concurrencyLvl) {
+        locks = new PaddedReentrantReadWriteLock[concurrencyLvl];
+
+        for (int i = 0; i < concurrencyLvl; i++)
             locks[i] = new PaddedReentrantReadWriteLock();
 
         compositeWriteLock = new CompositeWriteLock();
     }
 
+    /** {@inheritDoc} */
     @NotNull @Override public Lock readLock() {
-        int idx = (int)Thread.currentThread().getId() % locks.length;
+        int idx = Math.abs(COUNTER_UPD.getAndIncrement(this) % locks.length);
+
         return locks[idx].readLock();
     }
 
+    /** {@inheritDoc} */
     @NotNull @Override public Lock writeLock() {
         return compositeWriteLock;
     }
 
+    /**
+     * {@inheritDoc}
+     *
+     * Compared to {@link ReentrantReadWriteLock}, this class contains padding to ensure
that different instances will
+     * always be located in different CPU cache lines.
+     */
     private static class PaddedReentrantReadWriteLock extends ReentrantReadWriteLock {
 
+        /**
+         *
+         */
         private static final long serialVersionUID = 0L;
 
-        long p0, p1, p2, p3, p4, p5, p6, p7;
+        /**
+         * Padding.
+         */
+        private long p0, p1, p2, p3, p4, p5, p6, p7;
     }
 
+    /**
+     * {@inheritDoc}
+     *
+     * Methods of this class will lock all {@link #locks}.
+     */
     private class CompositeWriteLock implements Lock {
 
+        /** {@inheritDoc} */
         @Override public void lock() {
+            try {
+                lock(false);
+            } catch (InterruptedException e) {
+                // This should never happen.
+                throw new RuntimeException(e);
+            }
+        }
+
+        /** {@inheritDoc} */
+        @Override public void lockInterruptibly() throws InterruptedException {
+            lock(true);
+        }
+
+        /**
+         * @param interruptibly true if {@link Thread#interrupt()} should be considered.
+         * @throws InterruptedException
+         */
+        private void lock(boolean interruptibly) throws InterruptedException {
             int i = 0;
             try {
                 for (; i < locks.length; i++)
-                    locks[i].writeLock().lock();
+                    if (interruptibly)
+                        locks[i].writeLock().lockInterruptibly();
+                    else
+                        locks[i].writeLock().lock();
             }
             catch (Throwable e) {
                 for (i--; i >= 0; i--)
@@ -58,11 +144,18 @@ public class StripedCompositeReadWriteLock implements ReadWriteLock {
             }
         }
 
-        @Override public void lockInterruptibly() throws InterruptedException {
+        /** {@inheritDoc} */
+        @Override public boolean tryLock() {
             int i = 0;
+
+            boolean unlock = false;
+
             try {
                 for (; i < locks.length; i++)
-                    locks[i].writeLock().lockInterruptibly();
+                    if (!locks[i].writeLock().tryLock()) {
+                        unlock = true;
+                        break;
+                    }
             }
             catch (Throwable e) {
                 for (i--; i >= 0; i--)
@@ -70,19 +163,38 @@ public class StripedCompositeReadWriteLock implements ReadWriteLock {
 
                 throw e;
             }
+
+            if (unlock) {
+                for (i--; i >= 0; i--)
+                    locks[i].writeLock().unlock();
+
+                return false;
+            }
+
+            return true;
         }
 
-        @Override public boolean tryLock() {
+        /** {@inheritDoc} */
+        @Override public boolean tryLock(long time, TimeUnit unit) throws InterruptedException
{
+            long timeLeft = unit.convert(time, TimeUnit.NANOSECONDS);
+
+            long prevTime = System.nanoTime();
+
             int i = 0;
 
             boolean unlock = false;
 
             try {
-                for (; i < locks.length; i++)
-                    if (!locks[i].writeLock().tryLock()) {
+                for (; i < locks.length; i++) {
+                    if (timeLeft < 0 || !locks[i].writeLock().tryLock(timeLeft, TimeUnit.NANOSECONDS))
{
                         unlock = true;
                         break;
                     }
+
+                    long currentTime = System.nanoTime();
+                    timeLeft -= (currentTime - prevTime);
+                    prevTime = currentTime;
+                }
             }
             catch (Throwable e) {
                 for (i--; i >= 0; i--)
@@ -94,23 +206,22 @@ public class StripedCompositeReadWriteLock implements ReadWriteLock {
             if (unlock) {
                 for (i--; i >= 0; i--)
                     locks[i].writeLock().unlock();
+
                 return false;
             }
 
             return true;
         }
 
-        @Override public boolean tryLock(long time, TimeUnit unit) throws InterruptedException
{
-            throw new RuntimeException("Not supported");
-        }
-
+        /** {@inheritDoc} */
         @Override public void unlock() {
             for (int i = locks.length - 1; i >= 0; i--)
                 locks[i].writeLock().unlock();
         }
 
+        /** {@inheritDoc} */
         @NotNull @Override public Condition newCondition() {
-            throw new RuntimeException("Not supported");
+            throw new UnsupportedOperationException();
         }
     }
 }


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