[ofw][patch][WinVerbs tests] Re: fix IPv6related connectionproblem

[Leonid Keller]

Seems like QueryPerformanceCounter is the most trustful thing for now.
One needs just not to forget that it takes its own time for work. :(


________________________________

	From: Diego Guella [mailto:diego.guella at sircomtech.com] 
	Sent: Thursday, February 19, 2009 12:00 PM
	To: Leonid Keller; Fab Tillier; Sean Hefty;
ofw at lists.openfabrics.org
	Subject: Re: [ofw][patch][WinVerbs tests] Re: fix IPv6related
connectionproblem 
	
	
	----- Original Message ----- 
	>From: "Leonid Keller"
	>> You can use the __rdtsc ...
	>We gave up this way.
	> __rdtsc is complained on the Web to be unstable function,
especially in
	>multi-processor environment.
	
	I am coding a test application right now, and faced the same
problem.
	I haven't found a real solution, and I'm interested in how you
will solve this.
	These are the informations I found:
	
	http://www.virtualdub.org/blog/pivot/entry.php?id=106
	
http://blogs.msdn.com/oldnewthing/archive/2008/09/08/8931563.aspx
	http://support.microsoft.com/kb/172338/en-us
	http://support.microsoft.com/kb/938448/en-us
	http://support.microsoft.com/kb/274323/en-us
	
	I'm still using QueryPerformanceCounter right now, but I don't
really know how much trust to put in it.
	
	>If it is that simple why didn't Microsoft use it in
	>QueryPerformanceCounter implementation ? :(
	>
	>Let's formulate our problem:
	>We have to measure a very fast process and the time T of the
	>time stamping itself influence the results.
	>
	>Possible solutions:
	>1. Exclude T from the result by some artificial trick. (as in
the
	>discussed patch)
	>2. Measure T before the loop and subtract after.
	>3. Make stampings once in N loops decreasing N times it's
influence.
	>4. ?
	>
	>What would you prefere ?
	>

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