我正在创建这个方法 issuesTransfer 来实现从一个帐户到另一个帐户的转账。
我的解决方案是:
public void issueTransfer(final int amount, final Account src,
final Account dst) {
/*
* TODO implement issueTransfer using object-based isolation instead of
* global isolation, based on the reference code provided in
* BankTransactionsUsingGlobalIsolation. Keep in mind that isolation
* must be applied to both src and dst.
*/
isolated(src, dst, () -> {
if (src.withdraw(amount)) {
dst.deposit(amount);
}
});
}
全局隔离的解决方案是:
public void issueTransfer(final int amount, final Account src,
final Account dst) {
isolated(() -> {
src.performTransfer(amount, dst);
});
}
应用的全局和对象隔离方法定义如下:
public static void isolated(Runnable runnable) {
isolatedManager.acquireAllLocks();
try {
runnable.run();
} finally {
isolatedManager.releaseAllLocks();
}
}
public static void isolated(Object obj1, Object obj2, Runnable runnable) {
Object[] objArr = new Object[]{obj1, obj2};
isolatedManager.acquireLocksFor(objArr);
try {
runnable.run();
} finally {
isolatedManager.releaseLocksFor(objArr);
}
}
辅助方法(获取和释放)是:
public void acquireAllLocks() {
for(int i = 0; i < this.locks.length; ++i) {
this.locks[i].lock();
}
}
public void releaseAllLocks() {
for(int i = this.locks.length - 1; i >= 0; --i) {
this.locks[i].unlock();
}
}
public void acquireLocksFor(Object[] objects) {
TreeSet<Object> sorted = this.createSortedObjects(objects);
Iterator var3 = sorted.iterator();
while(var3.hasNext()) {
Object obj = var3.next();
int lockIndex = this.lockIndexFor(obj);
this.locks[lockIndex].lock();
}
}
public void releaseLocksFor(Object[] objects) {
TreeSet<Object> sorted = this.createSortedObjects(objects);
Iterator var3 = sorted.iterator();
while(var3.hasNext()) {
Object obj = var3.next();
int lockIndex = this.lockIndexFor(obj);
this.locks[lockIndex].unlock();
}
}
private int lockIndexFor(Object obj) {
return Math.abs(obj.hashCode()) % 64;
}
private TreeSet<Object> createSortedObjects(Object[] objects) {
TreeSet<Object> sorted = new TreeSet(new Comparator<Object>() {
public int compare(Object o1, Object o2) {
return IsolatedManager.this.lockIndexFor(o1) - IsolatedManager.this.lockIndexFor(o2);
}
});
Object[] var3 = objects;
int var4 = objects.length;
for(int var5 = 0; var5 < var4; ++var5) {
Object obj = var3[var5];
sorted.add(obj);
}
return sorted;
}
正如您所看到的,我应该按照文档的要求应用第二种方法(对象隔离)。 测试顺利通过:
public void testObjectIsolation() {
testDriver(new BankTransactionsUsingGlobalIsolation());
final long globalTime = testDriver(
new BankTransactionsUsingGlobalIsolation());
testDriver(new BankTransactionsUsingObjectIsolation());
final long objectTime = testDriver(
new BankTransactionsUsingObjectIsolation());
final double improvement = (double)globalTime / (double)objectTime;
final int ncores = getNCores();
final double expected = (double)ncores * 0.75;
final String msg = String.format("Expected an improvement of at " +
"least %fx with object-based isolation, but saw %fx", expected,
improvement);
assertTrue(msg, improvement >= expected);
}
但是用于评估的平台表示我没有通过 2 核或 4 核测试。根据我执行此操作的时间,有时我会通过其中一项测试(我假设是 2 个核心测试。
正如您从我通过的测试中看到的,我的对象隔离解决方案比我的全局隔离更快(每个核心的比例为 1:0.75)。 是平台故障还是我的代码可以改进?我尝试过使用 lock、unlock 和 trylock,但我的解决方案似乎工作得更快,但还不够。
最佳答案
您可以尝试 Brian Goetz 和 Tim Pierels 所著的《Java 并发实践》中的方法
关于java - 如何在并发事务中实现高性能的对象隔离解决方案,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43714784/