From owner-freebsd-hackers  Thu Nov  2 12:17:32 2000
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Date: Thu, 2 Nov 2000 12:17:15 -0800 (PST)
From: Richard Hodges <rh@matriplex.com>
To: Hao Zhang <zhanghao@nortelnetworks.com>
Cc: "'freebsd-hackers@FreeBSD.ORG'" <freebsd-hackers@FreeBSD.ORG>
Subject: Re: high speed timestamp counter
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On Thu, 2 Nov 2000, Hao Zhang wrote:

> Hi there,
> 
> I am trying to read the on board Pentium Time Stamp Counter. Is there an API
> in Unix that allows me to read it directly?
> Or some assembly language line that I can drop into my code?
> 
> I need the high speed counters to profile some code. I don't want to use the
> classical time API that is provided in <time.h>

#define GET_RDTSC(var) {__asm__ volatile("rdtsc":"=A"(var)); }

{
  long long   timeval1, timeval2, diff;

  GET_RDTSC(timeval1);

  do_something();

  GET_RDTSC(timeval2);

  diff = timeval2 - timeval1;
}

Is this what you had in mind?

All the best,

-Richard   

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   Richard Hodges   | Matriplex, inc.
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