--- old/src/hotspot/share/gc/g1/g1GCPhaseTimes.cpp	2018-04-16 13:05:16.465438734 +0200
+++ new/src/hotspot/share/gc/g1/g1GCPhaseTimes.cpp	2018-04-16 13:05:16.200430608 +0200
@@ -483,7 +483,7 @@
 }
 
 G1EvacPhaseWithTrimTimeTracker::~G1EvacPhaseWithTrimTimeTracker() {
-  _total_time += (Ticks::now() - _start) + _pss->trim_ticks();
+  _total_time += (Ticks::now() - _start) - _pss->trim_ticks();
   _trim_time += _pss->trim_ticks();
   _pss->reset_trim_ticks();
 }
@@ -491,13 +491,13 @@
 G1GCParPhaseTimesTracker::G1GCParPhaseTimesTracker(G1GCPhaseTimes* phase_times, G1GCPhaseTimes::GCParPhases phase, uint worker_id) :
     _phase_times(phase_times), _phase(phase), _worker_id(worker_id) {
   if (_phase_times != NULL) {
-    _start_time = os::elapsedTime();
+    _start_time = Ticks::now();
   }
 }
 
 G1GCParPhaseTimesTracker::~G1GCParPhaseTimesTracker() {
   if (_phase_times != NULL) {
-    _phase_times->record_time_secs(_phase, _worker_id, os::elapsedTime() - _start_time);
+    _phase_times->record_time_secs(_phase, _worker_id, TicksToTimeHelper::seconds(Ticks::now() - _start_time));
   }
 }
 
@@ -513,7 +513,8 @@
 
 G1EvacPhaseTimesTracker::~G1EvacPhaseTimesTracker() {
   if (_phase_times != NULL) {
-    _start_time += TicksToTimeHelper::seconds(_trim_time);
+    // Exclude trim time by increasing the start time.
+    _start_time += _trim_time;
     _phase_times->record_or_add_objcopy_time_secs(_worker_id, TicksToTimeHelper::seconds(_trim_time));
   }
 }
--- old/src/hotspot/share/gc/g1/g1GCPhaseTimes.hpp	2018-04-16 13:05:17.578472865 +0200
+++ new/src/hotspot/share/gc/g1/g1GCPhaseTimes.hpp	2018-04-16 13:05:17.314464769 +0200
@@ -379,7 +379,7 @@
 
 class G1GCParPhaseTimesTracker : public CHeapObj<mtGC> {
 protected:
-  double _start_time;
+  Ticks _start_time;
   G1GCPhaseTimes::GCParPhases _phase;
   G1GCPhaseTimes* _phase_times;
   uint _worker_id;
--- old/src/hotspot/share/gc/g1/g1ParScanThreadState.cpp	2018-04-16 13:05:18.799510308 +0200
+++ new/src/hotspot/share/gc/g1/g1ParScanThreadState.cpp	2018-04-16 13:05:18.475500372 +0200
@@ -49,8 +49,8 @@
     _scanner(g1h, this),
     _hash_seed(17),
     _worker_id(worker_id),
-    _stack_drain_upper_threshold(GCDrainStackTargetSize * 2 + 1),
-    _stack_drain_lower_threshold(GCDrainStackTargetSize),
+    _stack_trim_upper_threshold(GCDrainStackTargetSize * 2 + 1),
+    _stack_trim_lower_threshold(GCDrainStackTargetSize),
     _trim_ticks(),
     _old_gen_is_full(false)
 {
--- old/src/hotspot/share/gc/g1/g1ParScanThreadState.hpp	2018-04-16 13:05:19.977546432 +0200
+++ new/src/hotspot/share/gc/g1/g1ParScanThreadState.hpp	2018-04-16 13:05:19.685537477 +0200
@@ -61,8 +61,8 @@
   uint _worker_id;
 
   // Upper and lower threshold to start and end work queue draining.
-  uint const _stack_drain_upper_threshold;
-  uint const _stack_drain_lower_threshold;
+  uint const _stack_trim_upper_threshold;
+  uint const _stack_trim_lower_threshold;
 
   Tickspan _trim_ticks;
   // Map from young-age-index (0 == not young, 1 is youngest) to
--- old/src/hotspot/share/gc/g1/g1ParScanThreadState.inline.hpp	2018-04-16 13:05:21.111581207 +0200
+++ new/src/hotspot/share/gc/g1/g1ParScanThreadState.inline.hpp	2018-04-16 13:05:20.827572498 +0200
@@ -153,11 +153,11 @@
 }
 
 inline bool G1ParScanThreadState::needs_partial_trimming() const {
-  return !_refs->overflow_empty() || _refs->size() > _stack_drain_upper_threshold;
+  return !_refs->overflow_empty() || _refs->size() > _stack_trim_upper_threshold;
 }
 
 inline bool G1ParScanThreadState::is_partially_trimmed() const {
-  return _refs->overflow_empty() && _refs->size() <= _stack_drain_lower_threshold;
+  return _refs->overflow_empty() && _refs->size() <= _stack_trim_lower_threshold;
 }
 
 inline void G1ParScanThreadState::trim_queue_to_threshold(uint threshold) {
@@ -181,7 +181,7 @@
 
   const Ticks start = Ticks::now();
   do {
-    trim_queue_to_threshold(_stack_drain_lower_threshold);
+    trim_queue_to_threshold(_stack_trim_lower_threshold);
   } while (!is_partially_trimmed());
   _trim_ticks += Ticks::now() - start;
 }
--- old/src/hotspot/share/utilities/ticks.hpp	2018-04-16 13:05:22.230615521 +0200
+++ new/src/hotspot/share/utilities/ticks.hpp	2018-04-16 13:05:21.963607334 +0200
@@ -47,6 +47,11 @@
     return *this;
   }
 
+  Tickspan& operator-=(const Tickspan& rhs) {
+    _span_ticks -= rhs._span_ticks;
+    return *this;
+  }
+
   jlong value() const {
     return _span_ticks;
   }
--- old/src/hotspot/share/utilities/ticks.inline.hpp	2018-04-16 13:05:23.344649683 +0200
+++ new/src/hotspot/share/utilities/ticks.inline.hpp	2018-04-16 13:05:23.079641557 +0200
@@ -33,7 +33,7 @@
 }
 
 inline Tickspan operator-(Tickspan lhs, Tickspan rhs) {
-  lhs += rhs;
+  lhs -= rhs;
   return lhs;
 }