抱歉问题比较长,但其中涉及到Jon Skeet的参考信息,对于某些人来说可能是值得的。
简而言之:
在Mono框架中运行时,Interlocked.Read
/ Interlocked.Exchange
似乎比在.NET框架中运行时执行速度慢得多。我想知道是为什么。
详细解释:
我想要一个适用于32位平台的线程安全双精度浮点数,所以我创建了这个结构体:
public interface IThreadSafeDouble
{
double Value { get; set; }
}
public struct LockedThreadSafeDouble : IThreadSafeDouble
{
private readonly object Locker;
private double _Value;
public double Value
{
get { lock (Locker) return _Value; }
set { lock (Locker) _Value = value; }
}
public LockedThreadSafeDouble(object init)
: this()
{
Locker = new object();
}
}
当我阅读了Jon Skeet对于这个问题的回答后,我创建了以下这个结构体:
public struct InterlockedThreadSafeDouble : IThreadSafeDouble
{
private long _Value;
public double Value
{
get { return BitConverter.Int64BitsToDouble(Interlocked.Read(ref _Value)); }
set { Interlocked.Exchange(ref _Value, BitConverter.DoubleToInt64Bits(value)); }
}
}
然后我编写了这个测试:
private static TimeSpan ThreadSafeDoubleTest2(IThreadSafeDouble dbl)
{
var incrementTarg = 10000000;
var sw = new Stopwatch();
sw.Start();
for (var i = 0; i < incrementTarg; i++, dbl.Value++);
sw.Stop();
return sw.Elapsed;
}
private static void ThreadSafeTest()
{
var interlockedDbl = new InterlockedThreadSafeDouble();
var interlockedTim = ThreadSafeDoubleTest2(interlockedDbl);
var lockedDbl = new LockedThreadSafeDouble(true);
var lockedTim = ThreadSafeDoubleTest2(lockedDbl);
System.Console.WriteLine("Interlocked Time: " + interlockedTim);
System.Console.WriteLine("Locked Time: " + lockedTim);
}
public static void Main(string[] args)
{
for (var i = 0; i < 5; i++)
{
System.Console.WriteLine("Test #" + (i + 1));
ThreadSafeTest();
}
System.Console.WriteLine("Done testing.");
System.Console.ReadLine();
}
使用.NET框架,我得到了以下结果:
![.NET Interlocked test results](https://istack.dev59.com/QFvz9.webp)
![Mono Interlocked test results](https://istack.dev59.com/Qme8Q.webp)
更新: 我编写了以下更简单的测试:
long val = 1;
var sw = new Stopwatch();
sw.Start();
for (var i = 0; i < 100000000; i++) {
Interlocked.Exchange(ref val, 2);
// Interlocked.Read(ref val);
}
sw.Stop();
System.Console.WriteLine("Time: " + sw.Elapsed);
使用.NET框架,无论是Exchange
还是Read
操作,平均响应时间都在约2.5秒左右。而使用Mono框架,则平均响应时间为约5.1秒。