为什么.NET计时器限制为15毫秒的分辨率？开发者社区

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using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading;
namespace TimerTest
    class Program
        const int TickFrequency = 5;
        const int TestDuration = 15000;   // 15 seconds
        static void Main(string[] args)
            // Create a list to hold the tick times
            // The list is pre-allocated to prevent list resizing
            // from slowing down the test.
            List<double> tickTimes = new List<double>(2 * TestDuration / TickFrequency);
            // Start a stopwatch so we can keep track of how long this takes.
            Stopwatch Elapsed = Stopwatch.StartNew();
            // Create a timer that saves the elapsed time at each tick
            Timer ticker = new Timer((s) =>
                    tickTimes.Add(Elapsed.ElapsedMilliseconds);
                }, null, 0, TickFrequency);
            // Wait for the test to complete
            Thread.Sleep(TestDuration);
            // Destroy the timer and stop the stopwatch
            ticker.Dispose();
            Elapsed.Stop();
            // Now let's analyze the results
            Console.WriteLine("{0:N0} ticks in {1:N0} milliseconds", tickTimes.Count, Elapsed.ElapsedMilliseconds);
            Console.WriteLine("Average tick frequency = {0:N2} ms", (double)Elapsed.ElapsedMilliseconds / tickTimes.Count);
            // Compute min and max deviation from requested frequency
            double minDiff = double.MaxValue;
            double maxDiff = double.MinValue;
            for (int i = 1; i < tickTimes.Count; ++i)
                double diff = (tickTimes[i] - tickTimes[i - 1]) - TickFrequency;
                minDiff = Math.Min(diff, minDiff);
                maxDiff = Math.Max(diff, maxDiff);
            Console.WriteLine("min diff = {0:N4} ms", minDiff);
            Console.WriteLine("max diff = {0:N4} ms", maxDiff);
            Console.WriteLine("Test complete.  Press Enter.");
            Console.ReadLine();
}

#define TARGET_RESOLUTION 1         // 1-millisecond target resolution
TIMECAPS tc;
UINT     wTimerRes;
if (timeGetDevCaps(&tc, sizeof(TIMECAPS)) != TIMERR_NOERROR) 
   // Error; application can't continue.
wTimerRes = min(max(tc.wPeriodMin, TARGET_RESOLUTION), tc.wPeriodMax);
timeBeginPeriod(wTimerRes); 
//       do your stuff here at approx. 1 ms timer resolution
timeEndPeriod(wTimerRes);

#define STATUS_SUCCESS 0
#define STATUS_TIMER_RESOLUTION_NOT_SET 0xC0000245
// after loading NtSetTimerResolution from ntdll.dll:
// The requested resolution in 100 ns units:
ULONG DesiredResolution = 5000;  
// Note: The supported resolutions can be obtained by a call to NtQueryTimerResolution()
ULONG CurrentResolution = 0;
// 1. Requesting a higher resolution
// Note: This call is similar to timeBeginPeriod.
// However, it to to specify the resolution in 100 ns units.
if (NtSetTimerResolution(DesiredResolution ,TRUE,&CurrentResolution) != STATUS_SUCCESS) {
    // The call has failed
printf("CurrentResolution [100 ns units]: %d\n",CurrentResolution);
// this will show 5000 on more modern platforms (0.5ms!)
//       do your stuff here at 0.5 ms timer resolution
// 2. Releasing the requested resolution
// Note: This call is similar to timeEndPeriod 
switch (NtSetTimerResolution(DesiredResolution ,FALSE,&CurrentResolution) {
    case STATUS_SUCCESS:
        printf("The current resolution has returned to %d [100 ns units]\n",CurrentResolution);
        break;
    case STATUS_TIMER_RESOLUTION_NOT_SET:
        printf("The requested resolution was not set\n");   
        // the resolution can only return to a previous value by means of FALSE

问 为什么.NET计时器限制为15毫秒的分辨率？ EN

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