RE: Re[2]: [GD-Windows] Performance timing

[Simon O'C. <si...@sc...>]

Hi Carl,


Have a search around nVidia's developer website
(http://developer.nvidia.com), IIRC they did presentation surveying each of
the major timing methods with regard to using them to profile code and the
advantages and disadvantages plus latencies of each.


If you decide to use any of the Windows OS timing functions, be sure to
search the KnowledgeBase on MSDN for the function names. There are a number
of known issues (many Jon has covered in his post already) detailed in the
KB; including which OSes and hardware the issues show up on and any known
work-arounds.

IIRC QueryPerformanceCounter() will perform its timing in different ways
depending on the OS version, whether SMP is in use, whether speed stepping
is present, what motherboard hardware is present etc. ISTR a post from one
of the MS guys on DirectXDev in about 1999 mentioning this (should still be
in the archives for that list).


Cheers,

Simon O'Connor
Programmer @ Acclaim
& Microsoft DirectX MVP  

> -----Original Message-----
> From: gam...@li... 
> [mailto:gam...@li...] On 
> Behalf Of Carl Bevil
> Sent: 11 February 2004 00:01
> To: Jon Watte
> Subject: Re[2]: [GD-Windows] Performance timing
> 
> Hi Jon,
> 
> > "Intel specific" as in specific to x86 architecture, specific to 
> > Windows, or specific to Intel chips?
> 
> Specific to Intel chips.  For some reason I had it in my head 
> that some of these methods only worked on "genuine Intel" 
> chips, but not on, say, AMD chips.
> 
> [...]
> > timeGetTime() and QueryPerformanceCounter() must go out on 
> the (I/O) 
> > bus, and thus take like a microsecond each. RDTSC is just a 
> flush and 
> > register read; on the order of 30-100 CPU clocks depending 
> on how anal 
> > you are about serializing when measuring. VASTLY preferrable :-)
> 
> Wow, thanks for this information.  More than I expected, and 
> very helpful!
> 
> Carl
> 
> 
> 
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