thoughts on timestamp problems

Brian Ford Brian.Ford@FlightSafety.com
Fri Oct 16 15:36:00 GMT 2009


On Fri, 16 Oct 2009, Eric Blake wrote:

> Then there was this web page:
> http://www.geisswerks.com/ryan/FAQS/timing.html
> which suggests a way to use a mixture of timeGetTime and
> QueryPerformanceCounter to get sub-millesecond sleep accuracy without the
> penalty of calling timeBeginPeriod (in other words, use normal millisecond
> granularity to burn most of the time down, then QueryPerformanceCounter to
> get the rest of the way without burning processor time for the bulk of the
> sleep).

I would strongly discourage a "high resolution sleep" in Cygwin using this
method.  If a particular application deems it necessary, they can always
do this.  But, a 1 - 15 ms CPU burn to provide high resolution "sleeps" is
not something an OS or OS emulation layer should be doing.  To me,
timeBeginPeriod is a way better solution because it doesn't cause CPU burn
(Yes, I know it increases interrupt tick processing overhead).  Don't ever
emulate sleep with burn in a library without fully exposing this to the
developer please.  The future is a multi-threaded multi-tasking world
where resources should NOT be wasted like this unless absolutely required.

-- 
Brian Ford
Staff Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained crew...



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