最适合正确测量缓存访问时间的计时器

Question

There exist so many timers which can be used to find time taken to execute a task or a program takes to complete its execution for example.

I would like to find the access time of L2 cache set by set by accessing array elements loaded into cache . To find the access time of all sets of L2 cache set by set time calculation , I have tried different options like - rdtsc(), gettimeofday () , but not getting exact result as expected .

I am using intel i7 machine in linux with gcc 4.8. What is the best timer to calculate the cache access time with more accuracy.

my approach is as follow

for ( j=0; j<100000;j++
{

for ( set_no = 0 ; set_no< 4096; set_no ++)
{ 

start= rdtsc()
{
access all blocks of a set = set_no;
}
end = rdtsc()


time_taken[set_no]+= end -start ;
}
}

for(set_no=0;set_no<4096;set_no++)
printf(" time needed for access set %d = %llu", set_no, time_taken[set_no]/100000);

I would like to know whether BEST/SUITABLE Timer available in C or C++ ?

I need to prevent out-of_order execution in i3/i7 to get correct time measurement, so * SERIALIZATION of timer is required. * Which timer should I use to get correct result with SERIALIZED OUTPUT. rdtsc() has OPTION to serialized the timer output, DOES other timer also have the same ?

should I use other option to calculate time to get better result ? Thanks in advance.

Answer 1

Since your compiler is capable of C++11, I'd go with std::chrono::high_resolution_clock. For http://en.cppreference.com/w/cpp/chrono/high_resolution_clock tells:

Class std::chrono::high_resolution_clock represents the clock with the smallest tick period provided by the implementation.