Start probing page fault behaviour

haversine_02/src/memtester/main.c

@@ -0,0 +1,62 @@
+#include "aliases.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/resource.h>
+#include <sys/time.h>
+
+#define PAGESIZE 4096
+
+typedef struct rusage rusage_t;
+
+u64 page_fault_count() {
+  rusage_t usage;
+
+  getrusage(RUSAGE_SELF, &usage);
+
+  return usage.ru_minflt + usage.ru_majflt;
+}
+
+int main(int argc, char *argv[]) {
+  if (argc < 2 || argc > 2) {
+    printf("Usage: %s [NUMBER OF PAGES TO ALLOCATE]\n", argv[0]);
+
+    return EXIT_FAILURE;
+  }
+
+  u64 page_count = atol(argv[1]);
+  u64 alloc_size = page_count * PAGESIZE;
+  u64 touch_size = 0;
+
+  printf("Page Count,Touch Count,Fault Count,Extra Faults\n");
+
+  for (u64 touch_count = 0; touch_count <= page_count; ++touch_count) {
+    touch_size = touch_count * PAGESIZE;
+
+    u8 *data = (u8 *)mmap(NULL, alloc_size, PROT_READ | PROT_WRITE,
+                          MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+    if (!data) {
+      printf("Failed to allocate memory\n");
+
+      return EXIT_FAILURE;
+    }
+
+    u64 fault_start = page_fault_count();
+
+    for (u64 i = 0; i < touch_size; ++i) {
+      data[i] = (u8)i;
+    }
+
+    u64 fault_end = page_fault_count();
+
+    u64 faults = fault_end - fault_start;
+
+    printf("%lu,%lu,%lu,%ld\n", page_count, touch_count, faults,
+           ((i64)faults - touch_count));
+
+    munmap((void *)data, alloc_size);
+  }
+
+  return EXIT_SUCCESS;
+}