169 lines
4.6 KiB
C
169 lines
4.6 KiB
C
/* ==================================================================== *
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* *
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* membench.c -- Measurement of the performance of the memory *
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* hierarchy. *
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* *
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* ==================================================================== */
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#include <unistd.h>
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#include <stdio.h>
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#include <sys/resource.h>
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#include <sys/times.h>
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#include <sys/time.h>
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#include <sys/types.h>
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#include <time.h>
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#include <limits.h>
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#define CACHE_MIN (128) /* smallest cache */
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#define CACHE_MAX (16 * 1024 * 1024) /* largest cache */
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#define SAMPLE 10 /* to get larger time sample */
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int x[CACHE_MAX]; /* stride thru this array */
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/**
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* Get the number of CPU ticks since last booting the computer
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*/
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inline unsigned long long getCPUTick (void)
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{
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unsigned lo, hi;
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asm volatile ("rdtsc" : "=a" (lo), "=d" (hi));
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return (unsigned long long) hi << 32 | lo;
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}
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/**
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* Get the current system time in milliseconds
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*/
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unsigned long timeGetTime (void)
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{
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/* Using Linux Time Functions To Determine Time */
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struct timeval tv;
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gettimeofday (&tv, 0);
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return tv.tv_sec * 1000 + tv.tv_usec / 1000;
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}
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/**
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* Determine the CPU clock speed.
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* @param nTime The time in milliseconds used to perform the measurement
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*/
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unsigned long getCPUSpeed (long nTime)
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{
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long long timeStart, timeStop;
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long long startTick, endTick;
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long long overhead = getCPUTick () - getCPUTick ();
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/* Calculate Starting Time And Start Tick */
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timeStart = timeGetTime ();
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while (timeGetTime () == timeStart)
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timeStart = timeGetTime();
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while (1)
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{
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timeStop = timeGetTime ();
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if ((timeStop - timeStart) > 1)
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{
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startTick = getCPUTick ();
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break;
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}
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}
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/* Calculate Stop Time And End Tick */
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timeStart = timeStop;
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while (1)
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{
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timeStop = timeGetTime();
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if ((timeStop - timeStart) > nTime)
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{
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endTick = getCPUTick();
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break;
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}
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}
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/* Return The Processors Speed In Hertz */
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return (unsigned long) ((endTick - startTick) + (overhead));
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}
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int main ()
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{
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int register i, index, stride, limit, temp;
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long steps, tsteps;
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int csize;
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/* timing variables */
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double sec;
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/* number of processor cycles used */
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unsigned long long cycles0, cycles;
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/* The CPU speed in Hz */
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unsigned long nHz = getCPUSpeed (1000);
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for (csize = CACHE_MIN; csize <= CACHE_MAX; csize <<= 1)
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{
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for (stride = 1; stride <= csize / 2; stride <<= 1)
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{
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/* init cycles counter */
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cycles = 0;
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/* cache size this loop */
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limit = csize - stride + 1;
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steps = 0;
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do
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{
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cycles0 = getCPUTick ();
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for (i = SAMPLE * stride; i != 0; i--)
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{
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/* larger sample */
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for (index = 0; index < limit; index += stride)
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{
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/* cache access */
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x[index] = x[index] + 1;
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}
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}
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/* count while loop iterations */
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steps++;
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cycles += getCPUTick () - cycles0;
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} while (cycles < nHz); /* repeat until collected 1 sec */
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sec = cycles / (double) nHz;
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/* repeat empty loop to subtract loop overhead */
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/* used to match # while iterations */
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tsteps = 0;
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/* repeat until same # iterations as above */
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do
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{
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cycles0 = getCPUTick ();
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for (i = SAMPLE * stride; i != 0; i--)
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{
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/* larger sample */
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for (index = 0; index < limit; index += stride)
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{
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/* dummy code */
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temp = temp + index;
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}
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}
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/* count while loop iterations */
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tsteps++;
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cycles -= getCPUTick () - cycles0;
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} while (tsteps < steps);
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printf ("Size:%7lu Stride:%7lu read+write:%10.3f ns, sec = %6.3f, cycles = %lld steps = %6.0f\n",
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csize * sizeof (int), stride * sizeof (int),
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(double) sec * 1e9 / (steps * SAMPLE * stride * ((limit - 1) / stride + 1)),
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sec, cycles, (double) steps);
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fflush(stdout);
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}
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printf ("\n\n");
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}
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return 0;
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}
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