Analyze contiguous physical memory chunks that mmap system call gives

physmem_alloc_analysis/physmem_alloc_profiler.cc

+// Copyright 2015, Google, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <assert.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+const size_t page_size = 1 << 12;
+
+uint64_t get_physical_frame_num(uintptr_t virtual_addr) {
+  int fd = open("/proc/self/pagemap", O_RDONLY);
+  assert(fd >= 0); 
+
+  off_t pos = lseek(fd, (virtual_addr / page_size) * 8, SEEK_SET);
+  assert(pos >= 0); 
+  uint64_t value;
+  int got = read(fd, &value, 8); 
+  assert(got == 8); 
+  int rc = close(fd);
+  assert(rc == 0); 
+
+  uint64_t frame_num = value & ((1ULL << 54) - 1); 
+  return frame_num;
+}
+
+int main(int argc, char **argv) {
+  size_t page_num = 256;
+  size_t sleep_sec = 30;
+
+  int c;
+  while ((c = getopt(argc, argv, "a:s:")) != -1) {
+    switch (c) {
+      case 'a':
+        page_num = atoi(optarg);
+        break;
+      case 's':
+        sleep_sec = atoi(optarg);
+        break;
+      default:
+        fprintf(stderr, "Usage: %s [-a alloc_size] [-s sleep_sec]\n", 
+                argv[0]);
+        exit(EXIT_FAILURE);
+    }
+  }
+
+  fprintf(stderr, "using allocation size: %lu pages\n", page_num);
+  fprintf(stderr, "using sleep interval: %lu seconds\n", sleep_sec);
+
+  FILE *out = fopen("physmem_alloc_results", "w+");
+  if (out == NULL) {
+    perror("open result file: ");
+    exit(EXIT_FAILURE);
+  }
+
+  size_t chunk_size = page_num * page_size; 
+  size_t iter = 0;
+
+  while (1) {
+    fprintf(stderr, "iteration %lu ... \n", iter); 
+    iter++;
+
+    char *chunk = (char *) mmap(
+        NULL, chunk_size, PROT_READ | PROT_WRITE,
+        MAP_POPULATE | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+    assert(chunk != MAP_FAILED);
+
+    for (size_t i = 0; i < page_num; i++) {
+      char *va = chunk + page_size * i;
+      uint64_t pfn = get_physical_frame_num((uintptr_t)va);
+      fprintf(out, "0x%" PRIx64 " ", pfn);
+    }
+
+    fprintf(out, "\n");
+    fflush(out);
+    int rc = munmap(chunk, chunk_size);
+    assert(rc == 0);
+    sleep(sleep_sec);
+  }
+  return 0;
+}