Update GC stats, ThreadPool, Timer and ScopedTimer to use monotonic time.

runtime/vm/scavenger.cc

 // Copyright (c) 2011, 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.
 
 #include "vm/scavenger.h"
 
 #include "vm/dart.h"
 #include "vm/dart_api_state.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
@@ skipping 486 matching lines @@
     // --gc_at_alloc can get us here before the ring has been initialized.
     ASSERT(FLAG_gc_at_alloc);
     return;
   }
   ring->VisitPointers(visitor);
 #endif  // !PRODUCT
 }
 
 
 void Scavenger::IterateRoots(Isolate* isolate, ScavengerVisitor* visitor) {
-  int64_t start = OS::GetCurrentTimeMicros();
+  int64_t start = OS::GetCurrentMonotonicMicros();
   isolate->VisitObjectPointers(visitor,
                                StackFrameIterator::kDontValidateFrames);
-  int64_t middle = OS::GetCurrentTimeMicros();
+  int64_t middle = OS::GetCurrentMonotonicMicros();
   IterateStoreBuffers(isolate, visitor);
   IterateObjectIdTable(isolate, visitor);
-  int64_t end = OS::GetCurrentTimeMicros();
+  int64_t end = OS::GetCurrentMonotonicMicros();
   heap_->RecordData(kToKBAfterStoreBuffer, RoundWordsToKB(UsedInWords()));
   heap_->RecordTime(kVisitIsolateRoots, middle - start);
   heap_->RecordTime(kIterateStoreBuffers, end - middle);
 }
 
 
 bool Scavenger::IsUnreachable(RawObject** p) {
   RawObject* raw_obj = *p;
   if (!raw_obj->IsHeapObject()) {
     return false;
@@ skipping 277 matching lines @@
       (survivor_end_ - FirstObjectStart()) / kWordSize;
   SemiSpace* from = Prologue(isolate, invoke_api_callbacks);
   // The API prologue/epilogue may create/destroy zones, so we must not
   // depend on zone allocations surviving beyond the epilogue callback.
   {
     StackZone zone(thread);
     // Setup the visitor and run the scavenge.
     ScavengerVisitor visitor(isolate, this, from);
     page_space->AcquireDataLock();
     IterateRoots(isolate, &visitor);
-    int64_t start = OS::GetCurrentTimeMicros();
+    int64_t start = OS::GetCurrentMonotonicMicros();
     ProcessToSpace(&visitor);
-    int64_t middle = OS::GetCurrentTimeMicros();
+    int64_t middle = OS::GetCurrentMonotonicMicros();
     {
       TIMELINE_FUNCTION_GC_DURATION(thread, "WeakHandleProcessing");
       if (FLAG_background_finalization) {
         FinalizationQueue* queue = new FinalizationQueue();
         ScavengerWeakVisitor weak_visitor(thread, this, queue);
         IterateWeakRoots(isolate, &weak_visitor);
         if (queue->length() > 0) {
           Dart::thread_pool()->Run(new BackgroundFinalizer(isolate, queue));
         } else {
           delete queue;
         }
       } else {
         ScavengerWeakVisitor weak_visitor(thread, this, NULL);
         IterateWeakRoots(isolate, &weak_visitor);
       }
     }
     ProcessWeakReferences();
     page_space->ReleaseDataLock();
 
     // Scavenge finished. Run accounting.
-    int64_t end = OS::GetCurrentTimeMicros();
+    int64_t end = OS::GetCurrentMonotonicMicros();
     heap_->RecordTime(kProcessToSpace, middle - start);
     heap_->RecordTime(kIterateWeaks, end - middle);
     stats_history_.Add(ScavengeStats(
         start, end, usage_before, GetCurrentUsage(), promo_candidate_words,
         visitor.bytes_promoted() >> kWordSizeLog2));
   }
   Epilogue(isolate, from, invoke_api_callbacks);
 
   // TODO(koda): Make verification more compatible with concurrent sweep.
   if (FLAG_verify_after_gc && !FLAG_concurrent_sweep) {
@@ skipping 51 matching lines @@
 }
 
 
 void Scavenger::FreeExternal(intptr_t size) {
   ASSERT(size >= 0);
   external_size_ -= size;
   ASSERT(external_size_ >= 0);
 }
 
 }  // namespace dart