Template for using perf_event

perf_event_template.c

/*
 ============================================================================
 Name        : branch_mispred.c
 Author      : John Demme
 Version     : Mar 21, 2011
 Description : A template for perf_event. Requires Linux 2.6.32 or higher
 ============================================================================
*/

#define _GNU_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <fcntl.h>
#include <sys/file.h>
#include <sys/time.h>
#include <assert.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <linux/unistd.h>
#include <linux/perf_event.h>
#include <sys/ioctl.h>

//perf counter syscall
int perf_event_open(struct perf_event_attr * hw,
		    pid_t pid, int cpu, int grp, unsigned long flags)
{
    return syscall(__NR_perf_event_open, hw, pid, cpu, grp, flags);
}

// Setup info for perf_event
struct perf_event_attr attr[4];

// function implementation
int main(int argc, char * argv[]) {
  size_t i, y;
  uint64_t val1[4], val2[4];
  int fd[4], rc;

  attr[0].type = PERF_TYPE_HARDWARE;
  attr[0].config = PERF_COUNT_HW_CPU_CYCLES; /* generic PMU event*/
  attr[0].disabled = 0;
  fd[0] = perf_event_open(&attr[0], getpid(), -1, -1, 0);
  if (fd[0] < 0) {
    perror("Opening performance counter");
  }

  attr[1].type = PERF_TYPE_HARDWARE;
  attr[1].config = PERF_COUNT_HW_BRANCH_MISSES; /* generic PMU event*/
  attr[1].disabled = 0;
  fd[1] = perf_event_open(&attr[1], getpid(), -1, -1, 0);
  if (fd[1] < 0) {
    perror("Opening performance counter");
  }

  attr[2].type = PERF_TYPE_HARDWARE;
  attr[2].config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS; /* generic PMU event*/
  attr[2].disabled = 0;
  fd[2] = perf_event_open(&attr[2], getpid(), -1, -1, 0);
  if (fd[2] < 0) {
    perror("Opening performance counter");
  }

  attr[3].type = PERF_TYPE_HARDWARE;
  attr[3].config = PERF_COUNT_HW_INSTRUCTIONS; /* generic PMU event*/
  attr[3].disabled = 0;
  fd[3] = perf_event_open(&attr[3], getpid(), -1, -1, 0);
  if (fd[3] < 0) {
    perror("Opening performance counter");
  }

    // Tell Linux to start counting events
  asm volatile ("nop;"); // pseudo-barrier
  rc = read(fd[0], &val1[0], sizeof(val1[0]));  assert(rc);
  rc = read(fd[1], &val1[1], sizeof(val1[1]));  assert(rc);
  rc = read(fd[2], &val1[2], sizeof(val1[2]));  assert(rc);
  rc = read(fd[3], &val1[3], sizeof(val1[3]));  assert(rc);
  asm volatile ("nop;"); // pseudo-barrier
  
  // The loop we are measuring
  for (i=0; i<100000; i++) {
    if(i%3 == 0) {
      y += 1;
    }
  }

  // Read the counter
  asm volatile("nop;"); // pseudo-barrier
  rc = read(fd[0], &val2[0], sizeof(val2[0]));  assert(rc);
  rc = read(fd[1], &val2[1], sizeof(val2[1]));  assert(rc);
  rc = read(fd[2], &val2[2], sizeof(val2[2]));  assert(rc);
  rc = read(fd[3], &val2[3], sizeof(val2[3]));  assert(rc);
  assert(rc);
  asm volatile ("nop;"); // pseudo-barrier

  // Close the counter
  close(fd[0]);
  close(fd[1]);
  close(fd[2]);
  close(fd[3]);

  printf("CPU Cycles:           %lu \n", val2[0] - val1[0]);
  printf("Instructions:         %lu \n", val2[3] - val1[3]);
  printf("IPC:                  %lf\n", ((double)val2[3] - val1[3]) / (val2[0] - val1[0]));
  printf("Branch misses:        %lu \n", val2[1] - val1[1]);
  printf("Branch instructions:  %lu \n", val2[2] - val1[2]);
  printf("Branch mispred. rate: %lf%%\n", 100.0*((double)val2[1] - val1[1]) / (val2[2] - val1[2]));
  printf("\n");

  return 0;
}