[NOT TO COMMIT YET] Using proc/pid/status file contents to get process metrics in linux.

base/trace_event/process_memory_totals_dump_provider.cc

 // Copyright 2015 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.
 
 #include "base/trace_event/process_memory_totals_dump_provider.h"
 
 #include "base/process/process_metrics.h"
 #include "base/trace_event/process_memory_dump.h"
 #include "base/trace_event/process_memory_totals.h"
 
@@ skipping 16 matching lines @@
 
 namespace {
 
 ProcessMetrics* CreateProcessMetricsForCurrentProcess() {
 #if !defined(OS_MACOSX) || defined(OS_IOS)
   return ProcessMetrics::CreateProcessMetrics(GetCurrentProcessHandle());
 #else
   return ProcessMetrics::CreateProcessMetrics(GetCurrentProcessHandle(), NULL);
 #endif
 }
+
+bool ReadStatusFile(FILE* status_file, std::string* data) {
+  if (fseek(status_file, 0, SEEK_SET))
+    return false;
+  char buffer[4096];
+  buffer[0] = '\0';
+  int ret = fread(buffer, 1, sizeof(buffer), status_file);

[Primiano Tucci (use gerrit), 2015/10/07 10:25:34]

Use base::ReadFromFD, which is protected from EINTR

+  if (ret <= 0)
+    return false;
+  data->clear();
+  data->append(buffer, ret);
+  return true;
+}
+
 }  // namespace
 
 // static
 ProcessMemoryTotalsDumpProvider*
 ProcessMemoryTotalsDumpProvider::GetInstance() {
   return Singleton<
       ProcessMemoryTotalsDumpProvider,
       LeakySingletonTraits<ProcessMemoryTotalsDumpProvider>>::get();
 }
 
 ProcessMemoryTotalsDumpProvider::ProcessMemoryTotalsDumpProvider()
     : process_metrics_(CreateProcessMetricsForCurrentProcess()) {
 }
 
 ProcessMemoryTotalsDumpProvider::~ProcessMemoryTotalsDumpProvider() {
 }
 
 // Called at trace dump point time. Creates a snapshot the memory counters for
 // the current process.
 bool ProcessMemoryTotalsDumpProvider::OnMemoryDump(const MemoryDumpArgs& args,
                                                    ProcessMemoryDump* pmd) {
-  const uint64 rss_bytes = rss_bytes_for_testing
-                               ? rss_bytes_for_testing
-                               : process_metrics_->GetWorkingSetSize();
+  uint64 rss_bytes;
+  uint64 peak_rss_bytes = 0;
+  std::string status_contents;
 
-  uint64 peak_rss_bytes = 0;
+  if (UNLIKELY(rss_bytes_for_testing)) {
+    rss_bytes = rss_bytes_for_testing;
+  } else if (proc_status_file &&
+             ReadStatusFile(proc_status_file.get(), &status_contents)) {
+#if defined(OS_LINUX) || defeind(OS_ANDROID)
+    int res = ParseProcStatusAndGetField(status_contents, "VmRSS", &rss_bytes);
+    DCHECK(res);
+    res = ParseProcStatusAndGetField(status_contents, "VmHWM", &peak_rss_bytes);
+    DCHECK(res);
+#else
+    NOTREACHED();
+#endif
+  } else {
+    rss_bytes = process_metrics_->GetWorkingSetSize();
+#if !defined(OS_IOS)
+    peak_rss_bytes = process_metrics_->GetPeakWorkingSetSize();
+#endif
+  }
 
-#if !defined(OS_IOS)
-  peak_rss_bytes = process_metrics_->GetPeakWorkingSetSize();
 #if defined(OS_LINUX) || defined(OS_ANDROID)
   if (kernel_supports_rss_peak_reset) {
     // TODO(ssid): Fix crbug.com/461788 to write to the file from sandboxed
     // processes.
     int clear_refs_fd = open("/proc/self/clear_refs", O_WRONLY);
     if (clear_refs_fd > 0 &&
         WriteFileDescriptor(clear_refs_fd, kClearPeakRssCommand,
                             sizeof(kClearPeakRssCommand))) {
       pmd->process_totals()->set_is_peak_rss_resetable(true);
     } else {
       kernel_supports_rss_peak_reset = false;
     }
     close(clear_refs_fd);
   }
 #endif  // defined(OS_LINUX) || defined(OS_ANDROID)
-#endif  // !defined(OS_IOS)
 
   if (rss_bytes > 0) {
     pmd->process_totals()->set_resident_set_bytes(rss_bytes);
     pmd->process_totals()->set_peak_resident_set_bytes(peak_rss_bytes);
     pmd->set_has_process_totals();
     return true;
   }
 
   return false;
 }
 
 }  // namespace trace_event
 }  // namespace base