Restore "Add current rss and embedder name to Observatory"

runtime/bin/process_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #if !defined(DART_IO_DISABLED)
 
 #include "platform/globals.h"
 #if defined(HOST_OS_LINUX)
 
 #include "bin/process.h"
@@ skipping 842 matching lines @@
 }
 
 void Process::TerminateExitCodeHandler() {
   ExitCodeHandler::TerminateExitCodeThread();
 }
 
 intptr_t Process::CurrentProcessId() {
   return static_cast<intptr_t>(getpid());
 }
 
+static void SaveErrorAndClose(FILE* file) {
+  int actual_errno = errno;
+  fclose(file);
+  errno = actual_errno;
+}
+
 int64_t Process::CurrentRSS() {
   // The second value in /proc/self/statm is the current RSS in pages.
-  File* statm = File::Open("/proc/self/statm", File::kRead);
+  // It is not possible to use getrusage() because the interested fields are not
+  // implemented by the linux kernel.
+  FILE* statm = fopen("/proc/self/statm", "r");
   if (statm == NULL) {
     return -1;
   }
-  RefCntReleaseScope<File> releaser(statm);
-  const intptr_t statm_length = 1 * KB;
-  void* buffer = reinterpret_cast<void*>(Dart_ScopeAllocate(statm_length));
-  const intptr_t statm_read = statm->Read(buffer, statm_length);
-  if (statm_read <= 0) {
+  int64_t current_rss_pages = 0;
+  int matches = fscanf(statm, "%*s%" Pd64 "", &current_rss_pages);
+  if (matches != 1) {
+    SaveErrorAndClose(statm);
     return -1;
   }
-  int64_t current_rss_pages = 0;
-  int matches = sscanf(reinterpret_cast<char*>(buffer), "%*s%" Pd64 "",
-                       &current_rss_pages);
-  if (matches != 1) {
-    return -1;
-  }
+  fclose(statm);
   return current_rss_pages * getpagesize();
 }
 
 int64_t Process::MaxRSS() {
   struct rusage usage;
   usage.ru_maxrss = 0;
   int r = getrusage(RUSAGE_SELF, &usage);
   if (r < 0) {
     return -1;
   }
@@ skipping 105 matching lines @@
     sigaction(signal, &act, NULL);
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(HOST_OS_LINUX)
 
 #endif  // !defined(DART_IO_DISABLED)