问题:
为什么 System.Threading.Timer
保持 15 毫秒的分辨率,尽管操作系统时钟分辨率要精确得多?
在没有繁忙的 CPU 等待的情况下实现 1ms 计时事件分辨率的推荐方法是什么?
再次强调:系统计时器在我的案例中有 1ms 分辨率(与建议的重复问题相反)。所以这不是系统计时器解析的问题。因此,在所谓的重复问题中没有有用的信息。
背景:
似乎 .NET System.Threading.Timer
没有使用系统时钟分辨率 - 它保持约 15 毫秒的分辨率。尽管操作系统时钟(例如 Sleep
分辨率)要精确得多。
在我的机器上(当几乎闲置且有 4 个内核可运行时):
>Clockres.exe
ClockRes v2.0 - View the system clock resolution
Copyright (C) 2009 Mark Russinovich
SysInternals - www.sysinternals.com
Maximum timer interval: 15.625 ms
Minimum timer interval: 0.500 ms
Current timer interval: 1.001 ms
我的快速测试的输出:
Sleep test:
Average time delta: 2[ms] (from 993 cases)
System.Threading.Timer test:
Average time delta: 15[ms] (from 985 cases)
测试代码所在位置:
private static void TestSleepVsTimer(long millisecondsDifference, int repetions)
{
TimingEventsKeeper timingEventsKeeper = new TimingEventsKeeper();
timingEventsKeeper.Reset((int) millisecondsDifference, repetions);
while (!timingEventsKeeper.TestDoneEvent.IsSet)
{
timingEventsKeeper.CountNextEvent(null);
Thread.Sleep((int) millisecondsDifference);
}
Console.WriteLine("Sleep test: ");
timingEventsKeeper.Output();
timingEventsKeeper.Reset((int) millisecondsDifference, repetions);
Timer t = new Timer(timingEventsKeeper.CountNextEvent, null, TimeSpan.FromMilliseconds(1), TimeSpan.FromMilliseconds(1));
timingEventsKeeper.TestDoneEvent.Wait();
Console.WriteLine("System.Threading.Timer test: ");
timingEventsKeeper.Output();
}
private class TimingEventsKeeper
{
long _ticksSum = 0;
long _casesCount = 0;
long _minTicksDiff;
long _maxTicksDiff;
long _lastTicksCount;
int _repetitons;
public CountdownEvent TestDoneEvent = new CountdownEvent(0);
public void Reset(int millisecondsDifference, int repetitions)
{
_ticksSum = 0;
_casesCount = 0;
_minTicksDiff = millisecondsDifference * 10000;
_maxTicksDiff = millisecondsDifference * 10000;
_lastTicksCount = DateTime.UtcNow.Ticks;
_repetitons = repetitions;
TestDoneEvent.Reset(repetitions);
}
public void CountNextEvent(object unused)
{
long currTicksCount = DateTime.UtcNow.Ticks;
long diff = currTicksCount - _lastTicksCount;
_lastTicksCount = currTicksCount;
TestDoneEvent.Signal();
if (diff >= _maxTicksDiff)
{
_maxTicksDiff = diff;
return;
}
if (diff <= _minTicksDiff)
{
_minTicksDiff = diff;
return;
}
_casesCount++;
_ticksSum += diff;
}
public void Output()
{
if(_casesCount > 0)
Console.WriteLine("Average time delta: {0}[ms] (from {1} cases)", _ticksSum / _casesCount / 10000, _casesCount);
else
Console.WriteLine("No measured cases to calculate average");
}
}
public static class WinApi
{
/// <summary>TimeBeginPeriod(). See the Windows API documentation for details.</summary>
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Interoperability", "CA1401:PInvokesShouldNotBeVisible"), System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2118:ReviewSuppressUnmanagedCodeSecurityUsage"), SuppressUnmanagedCodeSecurity]
[DllImport("winmm.dll", EntryPoint = "timeBeginPeriod", SetLastError = true)]
public static extern uint TimeBeginPeriod(uint uMilliseconds);
/// <summary>TimeEndPeriod(). See the Windows API documentation for details.</summary>
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Interoperability", "CA1401:PInvokesShouldNotBeVisible"), System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2118:ReviewSuppressUnmanagedCodeSecurityUsage"), SuppressUnmanagedCodeSecurity]
[DllImport("winmm.dll", EntryPoint = "timeEndPeriod", SetLastError = true)]
public static extern uint TimeEndPeriod(uint uMilliseconds);
}
private static void Main(string[] args)
{
WinApi.TimeBeginPeriod(1);
TestSleepVsTimer(1, 1000);
WinApi.TimeEndPeriod(1);
}
编辑 1:
环境:
在 .NET 2.0、3.0、3.5(无 CountDownEvent)和 4.5 下的构建和发布版本上进行测试
在 Windows 8(内部版本 9200)、Server 2012(内部版本 9200)、Server 2008(内部版本 6001 SP1)上
Sleep
和 Timer
之间存在显着差异。
为什么这不是重复的:
正如我发布的那样 - 操作系统计时器分辨率设置为 1 毫秒(并且 Sleep
也没有表现出这种行为)。 因此,这不是操作系统计时器分辨率(中断频率)的错误 - 这是 System.Threading.Timer
特有的问题。
编辑 2:
(向代码添加了 TimeBeginPeriod
和 TimeEndPeriod
调用 - 以强制更改操作系统计时器分辨率)
最佳答案
使用派生自 WaitHandle 的同步类之一,例如 AutoResetEvent 或 ManualResetEvent,在调用 WaitOne() 方法时设置超时参数。
通过在循环中调用 WaitOne,您可以实现一个计时器。
您可以向等待句柄派生类发出信号以中断或中断计时器。
请注意,要更改分辨率,最好使用实现 IDisposable 的辅助类:
internal sealed class TimePeriod : IDisposable
{
private const string WINMM = "winmm.dll";
private static TIMECAPS timeCapabilities;
private static int inTimePeriod;
private readonly int period;
private int disposed;
[DllImport(WINMM, ExactSpelling = true)]
private static extern int timeGetDevCaps(ref TIMECAPS ptc, int cbtc);
[DllImport(WINMM, ExactSpelling = true)]
private static extern int timeBeginPeriod(int uPeriod);
[DllImport(WINMM, ExactSpelling = true)]
private static extern int timeEndPeriod(int uPeriod);
static TimePeriod()
{
int result = timeGetDevCaps(ref timeCapabilities, Marshal.SizeOf(typeof(TIMECAPS)));
if (result != 0)
{
throw new InvalidOperationException("The request to get time capabilities was not completed because an unexpected error with code " + result + " occured.");
}
}
internal TimePeriod(int period)
{
if (Interlocked.Increment(ref inTimePeriod) != 1)
{
Interlocked.Decrement(ref inTimePeriod);
throw new NotSupportedException("The process is already within a time period. Nested time periods are not supported.");
}
if (period < timeCapabilities.wPeriodMin || period > timeCapabilities.wPeriodMax)
{
throw new ArgumentOutOfRangeException("period", "The request to begin a time period was not completed because the resolution specified is out of range.");
}
int result = timeBeginPeriod(period);
if (result != 0)
{
throw new InvalidOperationException("The request to begin a time period was not completed because an unexpected error with code " + result + " occured.");
}
this.period = period;
}
internal static int MinimumPeriod
{
get
{
return timeCapabilities.wPeriodMin;
}
}
internal static int MaximumPeriod
{
get
{
return timeCapabilities.wPeriodMax;
}
}
internal int Period
{
get
{
if (this.disposed > 0)
{
throw new ObjectDisposedException("The time period instance has been disposed.");
}
return this.period;
}
}
public void Dispose()
{
if (Interlocked.Increment(ref this.disposed) == 1)
{
timeEndPeriod(this.period);
Interlocked.Decrement(ref inTimePeriod);
}
else
{
Interlocked.Decrement(ref this.disposed);
}
}
[StructLayout(LayoutKind.Sequential)]
private struct TIMECAPS
{
internal int wPeriodMin;
internal int wPeriodMax;
}
}
然后您可以使用:
using (new TimePeriod(1))
{
////...
}
尼克
关于c# - System.Threading.Timer 与 System.Threading.Thread.Sleep 解析 - .NET Timer 不使用系统时钟解析,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/23215970/