Added isolate + thread high watermark tracking to Observatory

runtime/vm/thread_registry.cc

Index: runtime/vm/thread_registry.cc
diff --git a/runtime/vm/thread_registry.cc b/runtime/vm/thread_registry.cc
index 4694cc06a8771c7590f5e378d8bb171aefb851f3..1483b131ec656200fca367f46a2028489d1b0baa 100644
--- a/runtime/vm/thread_registry.cc
+++ b/runtime/vm/thread_registry.cc
@@ -170,6 +170,7 @@ Thread* ThreadRegistry::GetFromFreelistLocked(Isolate* isolate) {
   return thread;
 }
 
+
 void ThreadRegistry::ReturnToFreelistLocked(Thread* thread) {
   ASSERT(thread != NULL);
   ASSERT(thread->os_thread_ == NULL);
@@ -181,4 +182,16 @@ void ThreadRegistry::ReturnToFreelistLocked(Thread* thread) {
   free_list_ = thread;
 }
 
+
+uint ThreadRegistry::ThreadHighWatermarksTotalLocked() const {
+  ASSERT(threads_lock()->IsOwnedByCurrentThread());
+  uint memory_high_watermarks_total = 0;
+  Thread* current = active_list_;
+  while (current != NULL) {
+    memory_high_watermarks_total += current->memory_high_watermark();
+    current = current->next_;
+  }
+  return memory_high_watermarks_total;

[siva, 2017/01/21 00:30:51]

Why is it necessary to sum up the high water marks of the threads here and add
it up in this fashion. This code is racy and triggers an error from a tsan run.


Is tracking the high water mark for the isolate critical, could we
not just display the high water mark of each thread?

+}
+
 }  // namespace dart