Precise GC time measurements.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 8cef1aea5394f07db103f61e639695339bcb8343..3fc0c55c3682d4e146e0ed5bc2de0ae4dfa2dcf8 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -6348,7 +6348,7 @@ void Heap::TearDown() {
     PrintF("\n");
     PrintF("gc_count=%d ", gc_count_);
     PrintF("mark_sweep_count=%d ", ms_count_);
-    PrintF("max_gc_pause=%d ", get_max_gc_pause());
+    PrintF("max_gc_pause=%.1f ", get_max_gc_pause());
     PrintF("total_gc_time=%d ", total_gc_time_ms_);
     PrintF("min_in_mutator=%d ", get_min_in_mutator());
     PrintF("max_alive_after_gc=%" V8_PTR_PREFIX "d ",
@@ -7033,7 +7033,7 @@ GCTracer::~GCTracer() {
   heap_->alive_after_last_gc_ = heap_->SizeOfObjects();
   heap_->last_gc_end_timestamp_ = OS::TimeCurrentMillis();
 
-  int time = static_cast<int>(heap_->last_gc_end_timestamp_ - start_time_);
+  float time = heap_->last_gc_end_timestamp_ - start_time_;
 
   // Update cumulative GC statistics if required.
   if (FLAG_print_cumulative_gc_stat) {
@@ -7070,7 +7070,7 @@ GCTracer::~GCTracer() {
            end_memory_size_mb);
 
     if (external_time > 0) PrintF("%d / ", external_time);
-    PrintF("%d ms", time);
+    PrintF("%.1f ms", time);
     if (steps_count_ > 0) {
       if (collector_ == SCAVENGER) {
         PrintF(" (+ %d ms in %d steps since last GC)",
@@ -7095,7 +7095,7 @@ GCTracer::~GCTracer() {
 
     PrintF(".\n");
   } else {
-    PrintF("pause=%d ", time);
+    PrintF("pause=%.1f ", time);
     PrintF("mutator=%d ", static_cast<int>(spent_in_mutator_));
     PrintF("gc=");
     switch (collector_) {