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[Manta] Re: Re: Re: Measuring packet tracing


Chronological Thread 
  • From: "Biagio Cosenza" < >
  • To: "Thiago Ize" < >
  • Cc:
  • Subject: [Manta] Re: Re: Re: Measuring packet tracing
  • Date: Fri, 3 Oct 2008 13:48:21 +0200
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At start I missed the point :(

I confused CPUTime class with CPUTimer class in Timer.h, where it's used the struct tms instead of the time stamp counter (edx:eax).
TimeViewSampler uses the CPUTime::currentSeconds(), where it's implemented with the time stamp counter.
It was my fault. I'm sorry.


I suppose that the two ways of reading the edx:eax are mainly similar. On my code, they both work.
Remark (for i386):
  • in CPUTime::currentSeconds()
    unsigned int a, d;
    asm volatile("rdtsc" : "=a" (a), "=d" (d));
    return static_cast<unsigned long long>(a) |
            (static_cast<unsigned long long>(d) << 32);
  • the other method
    unsigned long long int x;
         __asm__ volatile (".byte 0x0f, 0x31" : "=A" (x));
         return x;
Thanks, Biagio


On Thu, Oct 2, 2008 at 9:54 PM, Thiago Ize < " target="_blank"> > wrote:
Hi Biagio,
How is this different from the high resolution timers already in manta? See Core/Util/CPUTime.cc for the code. These are what are used by the TimeViewSampler.

Thiago


Biagio Cosenza wrote:
Thanks for your suggestions!

I have implemented a Timer class that uses an high resolution timer. In Pentium processor, it reads the current time-stamp counter variable with a specific instruction. It is based on Kazutomo's code http://www.mcs.anl.gov/~kazutomo/rdtsc.html .

As suggested by Abe, I also did a "scaling" of the given values.
Booth snapshots and code are enclosed. Maybe they can be useful to other people.

Thanks, Biagio

---
Biagio Cosenza
ISISLab, Dip. di Informatica ed Applicazioni "Renato M. Capocelli"
Universita' degli Studi di Salerno
http://www.dia.unisa.it/~cosenza



--
Biagio Cosenza
ISISLab, Dip. di Informatica ed Applicazioni "Renato M. Capocelli"
Universita' degli Studi di Salerno
http://www.dia.unisa.it/~cosenza


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