[PATCH] Multiple timer issues + new [PATCH]

ikartur@gmail.com ikartur@gmail.com
Fri Feb 19 09:02:00 GMT 2016


On Feb 19, 2016 2:35 AM, "john hood" <cgull@glup.org> wrote:

> There's some information on the web discussing issues with
> QueryPerformanceCounter()

QueryPerformanceCounter() is the officially recommended method for time interval measurements:



Best Regards,

-----Original Message-----
From: john hood <cgull@glup.org>
To: cygwin-patches@cygwin.com
Sent: Fri, 19 Feb 2016 2:35
Subject: Re: [PATCH] Multiple timer issues + new [PATCH]

On 2/18/16 6:39 PM, Irányossy Knoblauch Artúr wrote:
> The ntod timer (type hires_ns), however, is getting its time value
> from QueryPerformanceCounter(), which, according to the MSDN
> documentation, will provide a "time stamp that can be used for
> time-interval measurements" -- that is just what the doctor ordered.
> :-)

I have some interest in this because my work on select() may interact
with what you're doing here.

There's some information on the web discussing issues with
QueryPerformanceCounter(), for example
<http://www.virtualdub.org/blog/pivot/entry.php?id=106>.  This is mostly
an issue with CPUs available in the (I think) 2003-2006 time frame, such
as early AMD Athlons and early Intel Core iNNN and iNNNN CPUs.  Earlier
CPUs didn't have both changeable clock rates and RDTSC, and later CPUs
had RDTSC but the clock rate is constant for RDTSC.  It's also possible
that only some versions of Windows have issues in this area, maybe later
versions of Windows avoid this problem.  Does your code work properly in
this case?



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