Measuring amount of CPU time taken by a piece of code, in C on Unix/Linux

Question

Can clock() be used as a dependable API to measure time taken by CPU to execute a snippet of code? When verified usng times() / clock(), both do not seem to measure the CPU

Answer 1

Some info here on HP's page about high resolution timers. Also, same trick _Asm_mov_from_ar (_AREG_ITC); used in http://www.fftw.org/cycle.h too.

Have to confirm if this can really be the solution.

Sample prog, as tested on HP-UX 11.31:

bbb@m_001/tmp/prof > ./perf_ticks 1024
ticks-memset {func [1401.000000] inline [30.000000]} noop [9.000000]
bbb@m_001/tmp/prof > cat perf_ticks.c
#include 
#include 
#include 
#include 
#include 
#include "cycle.h" /* one from http://www.fftw.org/cycle.h */
void test_ticks(char* sbuf, int* len){
    memset((char*)sbuf,0,*len);
}
int main(int argc,char* argv[]){
        int len=atoi(argv[1]);
        char *sbuf=(char*)malloc(len);
        ticks t1,t2,t3,t4,t5,t6;
        t1 =getticks(); test_ticks(sbuf,&len); t2 =getticks();
        t3 =getticks(); memset((char*)sbuf,0,len); t4 =getticks();
        t5=getticks();;t6=getticks();
        printf("ticks-memset {func [%llf] inline [%llf]} noop [%llf]\n",
                          elapsed(t2,t1),elapsed(t4,t3),elapsed(t6,t5));
        free(sbuf); return 0;
}
bbb@m_001/tmp/prof >