Re: [boost] Re: Re: xtime and GetSystemTimeAsFileTime

From: Peter Dimov (pdimov_at_[hidden])
Date: 2002-07-02 06:35:36

From: "Johan Nilsson" <johan.nilsson_at_[hidden]>
>
> Anyway, as long as correlation between absolute system time (xtime is time
> elapsed since midnight, 1st of Jan 1970, or?) and sleep goodnight/wakeup
> times are a concern, you'd have to use the time increment acquired from
GSTA
> as timeGetTime() and QueryPerformanceCounter() et al simply returns a
> counter.

Yes, timeGetTime() et al are "monotonic time" and not UTC time; I don't know
why UTC was chosen for Boost.Threads.

> > QueryPerformanceCounter has better resolution, but is much less
reliable.
>
> Could you expand on the reliability stuff? I've been using QPC quite a
lot,
> and have seen no problems other than having a "lowly" 1.19MHz frequnecy on
> uniprocessor systems (where rdtsc isn't used for it's implementation).

There are documented problems with QPC jumping abruptly several seconds on
some chipsets; I haven't investigated it but some game developers have run
into the issue.

http://support.microsoft.com/default.aspx?scid=kb;EN-US;q274323