[Android] Introduce libheap_profiler for memory profiling.

tools/android/heap_profiler/hdump.c

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// The client dump tool for libheap_profiler. It attaches to a process (given
+// its pid) and dumps all the libheap_profiler tracking information in JSON.
+// The target process is frozen (SIGSTOP) while dumping, unless the -n opt.
+// is passed (in which case the caller is responsible for un/freezing).
+// The JSON output looks like this:
+// {
+//   "total_allocated": 908748493,   # Total bytes allocated and not freed.
+//   "num_allocs":      37542,       # Number of virtual memory areas (VMAs)
+//   "num_stacks":      3723,        # Number of allocation call-sites.
+//   "allocs":                       # Optional. Printed only with the -x arg.
+//   {
+//     1121435680: {"len": 17, "flags": 1, "stack": 0},
+//     ^             ^           ^         ^ Index of the corresponding entry
+//     |             |           |           in the next "stacks" section. The
+//     |             |           |           call site which created the vma.
+//     |             |           |
+//     |             |           +---------> Last arg of heap_profiler_alloc().
+//     |             +---------------------> Length of the VMA.
+//     +-----------------------------------> Start address of the VMA.
+//   },
+//   "stacks":
+//   {
+//      3: {"total": 17, "frames": [1074792772, 1100849864, 1100850688, ...]},

[bulach, 2014/06/09 17:23:28]

I suppose this is running on the device, right?
transmitting over adb can be slow, so I'd suggest minifying this..
say, "t" for "total", "f" for frames... (similarly above..).
also, remove all the neat indentation :)
it's much easier to prettify in the hsot side.

[Primiano Tucci (use gerrit), 2014/06/09 19:10:52]

Oh, nice point. It's a lot of data actually (perhaps I should consider catting
through gzip on the device)

+//      ^     ^          ^
+//      |     |          +-----> Stack frames (absolute virtual addresses).
+//      |     +----------------> Bytes allocated and not freed by the call site.
+//      +----------------------> Index of the entry (as for "allocs" xref).
+//                               Indexes might not be continuous or monotonic.
+
+#include <fcntl.h>
+#include <inttypes.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include "heap_profiler.h"
+
+
+static int dump_process_heap(int mem_fd, FILE* fmaps, bool dump_also_allocs);
+static void lseek_abs(int fd, size_t off);
+
+static int pid;
+
+// If the dump is interrupted, resume the target process before exiting.
+static void exit_handler() {
+  kill(pid, SIGCONT);
+  waitpid(pid, NULL, 0);
+  exit(-1);
+}
+
+int main(int argc, char** argv) {

[bulach, 2014/06/09 17:23:28]

I'd suggest moving the main to the bottom, and the other static functions above
it..
also, how about "heapdump.c" ?

[Primiano Tucci (use gerrit), 2014/06/09 19:10:52]

Done.
To be honest in the long term I consdider merging this into memdump. It's nicer
to have one device-side tool for all the memory operations. But it takes some
extra steps, let's do it later.

+  char c;
+  bool should_stop_process = true;
+  bool dump_also_allocs = false;
+
+  while (((c = getopt(argc, argv, "nx")) & 0x80) == 0) {
+   switch (c) {
+      case 'n':
+        should_stop_process = false;
+        break;
+      case 'x':
+        dump_also_allocs = true;
+        break;
+     }
+  }
+
+  if (optind >= argc) {
+    printf("Usage: %s [-n] [-x] pid\n", argv[0]);
+    return -1;
+  }
+
+  pid = atoi(argv[optind]);
+
+  if (should_stop_process) {
+    if (kill(pid, SIGSTOP) != 0) {
+      fprintf(stderr, "Could not freeze the target process.\n");
+      perror("kill");
+      return -1;
+    }
+    signal(SIGPIPE, exit_handler);
+    signal(SIGINT, exit_handler);

[bulach, 2014/06/09 17:23:28]

could split this into a few smaller functions, say |bool stop_process()| here..

+  }
+
+  // Wait for the process to actually freeze.
+  waitpid(pid, NULL, 0);
+
+  int ret = 0;
+  char path[64];
+  snprintf(path, sizeof(path), "/proc/%d/mem", pid);
+  int mem_fd = open(path, O_RDONLY);
+  if (mem_fd < 0) {
+    fprintf(stderr, "Could not attach to target process virtual memory.\n");
+    perror("open");
+    ret = -1;
+  }
+
+  snprintf(path, sizeof(path), "/proc/%d/maps", pid);
+  FILE* fmaps = fopen(path, "r");
+  if (fmaps == NULL) {
+    fprintf(stderr, "Could not open %s.\n", path);
+    perror("fopen");
+    ret = -1;
+  }

[bulach, 2014/06/09 17:23:28]

similarly, something like |get_mem_fd()|, and |get_maps()|

[Primiano Tucci (use gerrit), 2014/06/09 19:10:52]

Done.

+
+  if (ret == 0)
+    ret = dump_process_heap(mem_fd, fmaps, dump_also_allocs);
+
+  if (should_stop_process)
+    kill(pid, SIGCONT);
+
+  // Cleanup.
+  fflush(stdout);
+  close(mem_fd);
+  fclose(fmaps);
+  return ret;
+}
+
+static int dump_process_heap(int mem_fd, FILE* fmaps, bool dump_also_allocs) {
+  HeapStats stats;
+
+  // Look for the mmap which contains the HeapStats in the target process vmem.
+  // On Linux/Android, the libheap_profiler mmaps explicitly /dev/zero. The
+  // region furthermore starts with a magic marker to disambiguate.
+  bool stats_mmap_found = false;
+  for (;;) {
+    char line[1024];
+    if (fgets(line, sizeof(line), fmaps) == NULL)
+      break;
+
+    uintptr_t start;
+    uintptr_t end;
+    char map_file[32];
+    int ret = sscanf(line, "%"SCNxPTR"-%"SCNxPTR" rw-p %*s %*s %*s %31s",
+                     &start, &end, map_file);
+    const size_t size = end - start + 1;
+    if (ret != 3 || strcmp(map_file, "/dev/zero") != 0 || size < sizeof(stats))
+      continue;
+
+    // The mmap looks promising. Let's check for the magic marker.
+    lseek_abs(mem_fd, start);
+    if (read(mem_fd, &stats, sizeof(stats)) < sizeof(stats))
+      continue;
+
+    if (stats.magic_start == HEAP_PROFILER_MAGIC_MARKER) {
+      stats_mmap_found = true;
+      break;
+    }
+  }
+
+  if (!stats_mmap_found) {
+    fprintf(stderr, "Could not find the HeapStats area. "
+                    "It looks like libheap_profiler is not loaded.\n");
+    return -1;
+  }
+
+  // Print JSON-formatted output.
+  printf("{\n");
+  printf("  \"total_allocated\": %zu,\n", stats.total_alloc_bytes);
+  printf("  \"num_allocs\":      %"PRIu32",\n", stats.num_allocs);
+  printf("  \"num_stacks\":      %"PRIu32",\n", stats.num_stack_traces);
+
+  uint32_t dbg_counted_vmas = 0;
+  size_t dbg_counted_total_alloc_bytes = 0;
+  bool prepend_trailing_comma = false;  // JSON syntax, I hate you.
+  uint32_t i;
+
+  // Dump the optional allocation table.
+  if (dump_also_allocs) {
+    printf("  \"allocs\":\n");
+    printf("  {\n");
+    lseek_abs(mem_fd, (uintptr_t) stats.allocs);
+    for (i = 0; i < stats.max_allocs; ++i) {
+      VMA vma;
+      if (read(mem_fd, &vma, sizeof(vma)) != sizeof(vma)) {
+        fprintf(stderr, "ERROR: cannot read allocation table\n");
+        perror("read");
+        return -1;
+      }
+
+      // Skip empty (i.e. freed) entries.
+      if (vma.start == 0 && vma.end == 0)
+        continue;
+
+      if (vma.end < vma.start) {
+        fprintf(stderr, "ERROR: found inconsistent vma.\n");
+        return -1;
+      }
+
+      size_t vma_size = vma.end - vma.start + 1;
+      size_t stack_idx = ((uintptr_t) vma.st - (uintptr_t) stats.stack_traces) /
+                         sizeof(StacktraceEntry);
+      dbg_counted_total_alloc_bytes += vma_size;
+      ++dbg_counted_vmas;
+
+      if (prepend_trailing_comma)
+        printf(",\n");
+      prepend_trailing_comma = true;
+      printf("    %"PRIuPTR": "
+             "{\"len\": %zu, \"flags\": %"PRIu32", \"stack\": %zu}",
+             vma.start, vma_size, vma.flags, stack_idx);
+    }
+    printf("\n  },\n");
+
+    if (dbg_counted_vmas != stats.num_allocs) {
+      fprintf(stderr,
+              "ERROR: inconsistent alloc count (%"PRIu32" vs %"PRIu32").\n",
+              dbg_counted_vmas, stats.num_allocs);
+      return -1;
+    }
+
+    if (dbg_counted_total_alloc_bytes != stats.total_alloc_bytes) {
+      fprintf(stderr, "ERROR: inconsistent alloc totals (%zu vs %zu).\n",
+              dbg_counted_total_alloc_bytes, stats.total_alloc_bytes);
+      return -1;
+    }
+  }
+
+  // Dump the distinct stack traces.
+  printf("  \"stacks\":\n");
+  printf("  {\n");
+  prepend_trailing_comma = false;
+  dbg_counted_total_alloc_bytes = 0;
+  lseek_abs(mem_fd, (uintptr_t) stats.stack_traces);
+  for (i = 0; i < stats.max_stack_traces; ++i) {
+    StacktraceEntry st;
+    if (read(mem_fd, &st, sizeof(st)) != sizeof(st)) {
+      fprintf(stderr, "ERROR: cannot read stack trace table\n");
+      perror("read");
+      return -1;
+    }
+
+    // Skip empty (i.e. freed) entries.
+    if (st.alloc_bytes == 0)
+      continue;
+
+    dbg_counted_total_alloc_bytes += st.alloc_bytes;
+
+    if (prepend_trailing_comma)
+      printf(",\n");
+    prepend_trailing_comma = true;
+
+    printf("    %"PRIu32": {\"total\": %zu, \"frames\": [", i, st.alloc_bytes);
+    size_t n =
+     0;
+    for (;;) {
+      printf("%" PRIuPTR, st.frames[n]);
+      ++n;
+      if (n == HEAP_PROFILER_MAX_DEPTH || st.frames[n] == 0)
+        break;
+      else
+        printf(", ");
+    }
+    printf("]}");
+  }
+  printf("\n  }\n");
+  printf("}\n");
+
+  if (dbg_counted_total_alloc_bytes != stats.total_alloc_bytes) {
+    fprintf(stderr, "ERROR: inconsistent stacks totals (%zu vs %zu).\n",
+            dbg_counted_total_alloc_bytes, stats.total_alloc_bytes);
+    return -1;
+  }
+
+  fflush(stdout);
+  return 0;
+}
+
+// Unfortunately lseek takes a *signed* offset, which is unsuitable for large
+// files like /proc/X/mem on 64-bit.
+static void lseek_abs(int fd, size_t off) {
+#define OFF_T_MAX ((off_t) ~(((uint64_t) 1) << (8 * sizeof(off_t) - 1)))
+  if (off <= OFF_T_MAX) {
+    lseek(fd, (off_t) off, SEEK_SET);
+    return;
+  }
+  lseek(fd, (off_t) OFF_T_MAX, SEEK_SET);
+  lseek(fd, (off_t) (off - OFF_T_MAX), SEEK_CUR);
+}