sequential read/write speeds

On most POSIX systems, you can use clock.

#include <time.h>

clock_t start = clock();
do_some_work();
clock_t elapsed = clock() - start;

On x86 systems with inline assembly, you can use RDSTC.

long long __declspec(naked) tick()
{
    rdtsc;
}

long long start = tick();
do_some_work();
long long elapsed = tick() - start;

Another POSIX API is clock_gettime.

#include <unistd.h>
struct timeval start, elapsed;

clock_gettime(CLOCK_MONOTONIC, &start);
do_some_work();
clock_gettime(CLOCK_MONOTONIC, &elapsed);

if (start.tv_usec > elapsed.tv_usec)
elapsed.tv_sec--;
elapsed.tv_usec -= start.tv_usec;
elapsed.tv_sec -= start.tv_sec;

// elapsed contains elapsed time in seconds (tv_sec) and microseconds (tv_usec).
</unistd.h>