RDTSC use in C: Post: 302237580

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Top Forums Programming RDTSC use in C: Post 302237580 by GloriousDaisy on Thursday 18th of September 2008 12:58:16 AM

09-18-2008

Registered User

RDTSC use in C:

I have to use rdtsc on ubuntu for performance evaluation. But i am not getting the correct value. I am placing a sleep on 10 seconds, but value i get is some 1 sec... i dont know where im going wrong?

Code:

#include<sys/time.h>
#include<time.h>
#include<stdio.h>
typedef unsigned long long ticks;

static __inline__ ticks getticks(void)
{
     unsigned a, d;
     asm("cpuid");
     asm volatile("rdtsc" : "=a" (a), "=d" (d));

     return (((ticks)a) | (((ticks)d) << 32));
}
int main(){
     int r = 0;
     ticks tick,tick1,tickh;
     unsigned time =0;

     tick = getticks();
   
     sleep(10);
   
     tick1 = getticks();
   
     time = (unsigned)((tick1-tick)/1662543);
    printf("\ntime in MS%u\n",time);
return 0;
}

cat /proc/cpuinfo gives

Code:

pprocessor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 14
model name      : Genuine Intel(R) CPU           T2300  @ 1.66GHz
stepping        : 8
cpu MHz         : 1662.543
cache size      : 2048 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss tm pbe constant_tsc up arch_perfmon bts pni monitor vmx est tm2 xtpr
bogomips        : 3328.87
clflush size    : 64

Last edited by vino; 09-18-2008 at 03:45 AM.. Reason: added code tags

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sleep

SLEEP(3)						     Linux Programmer's Manual							  SLEEP(3)

NAME

       sleep - sleep for the specified number of seconds

SYNOPSIS

       #include <unistd.h>

       unsigned int sleep(unsigned int seconds);

DESCRIPTION

       sleep() makes the calling thread sleep until seconds seconds have elapsed or a signal arrives which is not ignored.

RETURN VALUE

       Zero if the requested time has elapsed, or the number of seconds left to sleep, if the call was interrupted by a signal handler.

CONFORMING TO

       POSIX.1-2001.

BUGS

       sleep() may be implemented using SIGALRM; mixing calls to alarm(2) and sleep() is a bad idea.

       Using longjmp(3) from a signal handler or modifying the handling of SIGALRM while sleeping will cause undefined results.

SEE ALSO

       alarm(2), nanosleep(2), signal(2), signal(7)

COLOPHON

       This  page is part of release 3.53 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

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								    2010-02-03								  SLEEP(3)