32位和64位Windows之间的日期时间粒度 [英] Datetime Granularity between 32bit and 64bit Windows
问题描述
我已经为网络调试创建了一个小的工程应用程序.它获取IP地址列表并对其进行ping操作，以及用户设置的超时和速率.它记录平均往返时间，每次发送失败时，都会记录其持续时间和发生时间的时间戳...
I have create a little engineering app for some network debugging. It takes a list of IP addresses and pings them, with user set timeout and rate. It logs the average round-trip time and every time one of the sends fails it logs it's duration of failure and a timestamp of when it happened...
就是这个想法.我在装有.Net4的Win7机器上开发了它，不得不将其放置在一组XP笔记本电脑上.
That's the idea. I developed it on a Win7 machine with .Net4 and have had to put the thing on a set of XP laptops.
问题是测试期间我的盒子上的持续时间值显示了不错的ms持续时间，在XP盒子上，当我看到它们的持续时间值显示为0或15.625(幻数?)...并在字符串中带有有趣的正方形，盒子符号时?
The problem is the duration values on my box during testing show nice ms durations, on the XP boxes when I look they show 0 or 15.625 (magic number?)... and have the funny square, box symbol in the string?
public void LinkUp()
{
if (_isLinkUp) return;
_upTime = DateTime.Now;
var span = _upTime.Subtract(_downTime);
_downTimeLog.Add(new LinkDown()
{
_span = span,
_status = _ipStatus,
_time = _downTime
});
_isLinkUp = true;
}
这就是做日志的部分._ipStatus是ping失败的原因(通常是超时).
That's the bit that does the log. The _ipStatus is the ping failure reason (typically timeout).
_downEventLog.AppendLine(" Duration-> " + linkDownLogEvent._span.TotalMilliseconds + "ms\n");
这就是打印的要点...有人可以阐明这一明显的区别吗?
That's the bit that does the print... Can anyone shed any light on this apparent difference?
问题已经回答，但我将在此处进行编辑以获取更多信息.
The question has been answered but I will include an edit here for some more info.
似乎差异不是归因于Win7和WinXP差异，而是32位和64位.
It seems that the difference was down not to the Win7 and WinXP difference but 32bit and 64bit.
在 Henk 指出的32位Windows系统中，系统时钟的粒度为15-16ms，对于每个小于16ms的时间值，这就是给我带来15.625的值的原因.
In a 32 bit windows systems as Henk points out, the granularity of the system clock is 15-16ms, this is what gave me the value of 15.625 for every value less than 16ms for the timespan.
在64位系统中，系统调用的是一组具有更精细粒度的不同方法.因此，在x64的开发机上，我的系统时钟具有ms精度！
In a 64 bit system the system call is to a different set of methods that have a much finer granularity. So on my dev machine in x64 I had ms accuracy from my system clock!
现在，秒表通过处理器工具使用硬件接口来记录更精细的粒度(可能不是每个处理器的滴答声，但我想这与这种想法相符.如果操作系统底层的硬件没有此级别的检测，则它将占用系统时间.所以要当心！但是我想大多数现代台式机/笔记本电脑都具有这种工具...嵌入式设备或类似性质的东西可能没有，但是就我所知，秒表类不在Compact Framework中(在这里，您必须使用QueryPerformanceCounter()).
Now, the stopwatch uses a hardware interface via the processor instrumentation to record a much finer granularity (probably not every processor tick, but I imagine something obscenely accurate in-line with this thinking). If the hardware underlying the OS does not have this level of instrumentation, it will however use the system time. So beware! But I would guess most modern desktops/laptops have this instrumentation... Embedded devices or things of that nature might not, but then the stopwatch class is not in the Compact Framework as far as I can see (here you have to use QueryPerformanceCounter()).
希望所有这些都对您有所帮助.这对我有很大帮助.
Hope all this helps. It's helped me a lot.
_spanStopWatch初始化程序周围的某处:
Somewhere around the _spanStopWatch initialiser:
if (!_spanStopWatch.IsHighResolution)
{
throw new ThisMachineIsNotAccurateEnoughForMyLikingException("Find a better machine.");
}
基本要点:
public void LinkUp()
{
if (_isLinkUp) return;
_spanStopWatch.Stop();
var span = _spanStopWatch.Elapsed;
_downTimeLog.Add(new LinkDown()
{
_span = span,
_status = _ipStatus,
_time = _downTime
});
_isLinkUp = true;
}
推荐答案
0或15.625(幻数?)
0 or 15.625 (magic number?)
是的，使用 DateTime.Now 仅精确到CPU时间片的长度(15-20毫秒，具体取决于您的硬件和操作系统版本).
Yes, using DateTime.Now is accurate only to the length of a CPU timeslice, 15-20 ms depending on your hardware and OS version.
使用 System.Diagnostics.Stopwatch 以获得更准确的计时.
Use System.Diagnostics.Stopwatch for more accurate timing.
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