bechmarking kernel code

[kernel coder]

hi,
    I'm profiling some part of kernel code.Mine profiling mechanism
is based on rdtsc instruction.

Please tell me if i'm profiling correctly.I'm teting linux kernel
2.6.15 and mine system is P4.


function(){

	unsigned long long c1,c2,c3,c4,c5;
	before=readtsc();
	before=readtsc();
	before=readtsc();
	overhead=readtsc()-before;
	c1=testfunc();
	c2=testfunc();
	c3=testfunc();
	c4=testfunc();
	c5=testfunc();

printk(" \n *c1 = %llu c2= %llu c3 = %llu c4 = %llu c5 = %llu overhead
=%llu",cycles1,cycles2,cycles3,cycles4,cycles5,overhead);


}

/***************************************/


unsigned long long readtsc(){
	unsigned long res[2]={0,0};
     __asm__ __volatile__  (
	      "rdtsc\n"
	       : "=a" (res[0]), "=d" (res[1]) );

	return *((unsigned long long *)res);

}

/*******************************************/

unsigned long long testfunc(){
	unsigned long start_cycles[2]={0,0};
	unsigned long end_cycles[2]={0,0};
	unsigned long long total_cycles=0;
	int i;
     __asm__ __volatile__  (               // read TSC, store edx:eax in res
	      "rdtsc\n"
	       : "=a" (start_cycles[0]), "=d" (start_cycles[1]) );


              /*  CODE TO BE PROFILED */


     __asm__ __volatile__  (               // read TSC, store edx:eax in res
	      "rdtsc\n"
	       : "=a" (end_cycles[0]), "=d" (end_cycles[1]) );
	total_cycles=*((unsigned long long *)end_cycles) - *((unsigned long
long *)start_cycles);
	return total_cycles;
}
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