diff --git a/main.c b/main.c
index e34e879..0608b07 100644
--- a/main.c
+++ b/main.c
@@ -7,6 +7,7 @@
 // bandwidth as advertised by the intel specs: 23.8 GiB/s (http://goo.gl/r8Aab)
 
 #include <assert.h>
+#include <errno.h>
 #include <math.h>
 #ifdef WITH_OPENMP
 #include <omp.h>
@@ -23,12 +24,18 @@
 #define SAMPLES 5
 #define TIMES 5
 #define BYTES_PER_GB (1024*1024*1024LL)
-#define SIZE (1*BYTES_PER_GB)
-#define PAGE_SIZE (1<<12)
+#define MAX_SIZE (1*BYTES_PER_GB)
+#ifndef PAGE_SIZE
+# define PAGE_SIZE (1<<12)
+#endif
+// NOTE(hholst): Use to set higher priority to avoid background or UI to interfere too much.
+#define RENICE (-10)
+
+static unsigned long long SIZE = MAX_SIZE;
 
 // This must be at least 32 byte aligned to make some AVX instructions happy.
 // Have PAGE_SIZE buffering so we don't have to do math for prefetching.
-char array[SIZE + PAGE_SIZE] __attribute__((aligned (32)));
+char array[MAX_SIZE] __attribute__((aligned (PAGE_SIZE)));
 
 // Compute the bandwidth in GiB/s.
 static inline double to_bw(size_t bytes, double secs) {
@@ -102,9 +109,14 @@ void timeit(void (*function)(void*, size_t), char* name) {
 
 int main() {
   memset(array, 0xFF, SIZE);  // un-ZFOD the page.
-  * ((uint64_t *) &array[SIZE]) = 0;
 
-  // TODO(awreece) iopl(0) and cli/sti?
+#ifdef RENICE
+  if (errno = 0, nice(RENICE) < 0 && errno != 0) {
+    perror("warning: failed to set process priority level");
+  }
+#endif
+
+  fprintf(stderr, "# Single-core performance. Threads: 1\n\n");
 
   timefun(read_memory_rep_lodsq);
   timefun(read_memory_loop);
@@ -129,9 +141,11 @@ int main() {
   timefun(write_memory_memset);
 
 #ifdef WITH_OPENMP
-
+  fprintf(stderr, "\n# Multi-core performance. Threads: %i\n\n", omp_get_max_threads());
+  unsigned long long npages_per_thread = (MAX_SIZE / omp_get_max_threads()) / PAGE_SIZE;
+  SIZE = PAGE_SIZE * npages_per_thread * omp_get_max_threads();
+  // fprintf(stderr, "OMP SIZE: %llu\n", SIZE);
   memset(array, 0xFF, SIZE);  // un-ZFOD the page.
-  * ((uint64_t *) &array[SIZE]) = 0;
 
   timefunp(read_memory_rep_lodsq);
   timefunp(read_memory_loop);