diff --git a/cmdline/cmdline_types.h b/cmdline/cmdline_types.h
index 9b4042c..f05648c 100644
--- a/cmdline/cmdline_types.h
+++ b/cmdline/cmdline_types.h
@@ -462,7 +462,7 @@
 struct XGcOption {
   // These defaults are used when the command line arguments for -Xgc:
   // are either omitted completely or partially.
-  gc::CollectorType collector_type_ =  kUseReadBarrier ?
+  gc::CollectorType collector_type_ = kUseReadBarrier ?
                                            // If RB is enabled (currently a build-time decision),
                                            // use CC as the default GC.
                                            gc::kCollectorTypeCC :
@@ -473,6 +473,7 @@
   bool verify_pre_gc_rosalloc_ = kIsDebugBuild;
   bool verify_pre_sweeping_rosalloc_ = false;
   bool verify_post_gc_rosalloc_ = false;
+  bool measure_ = kIsDebugBuild;
   bool gcstress_ = false;
 };
 
@@ -515,6 +516,8 @@
         xgc.gcstress_ = true;
       } else if (gc_option == "nogcstress") {
         xgc.gcstress_ = false;
+      } else if (gc_option == "measure") {
+        xgc.measure_ = true;
       } else if ((gc_option == "precise") ||
                  (gc_option == "noprecise") ||
                  (gc_option == "verifycardtable") ||
diff --git a/runtime/gc/collector/concurrent_copying-inl.h b/runtime/gc/collector/concurrent_copying-inl.h
index 3011112..4019a5b 100644
--- a/runtime/gc/collector/concurrent_copying-inl.h
+++ b/runtime/gc/collector/concurrent_copying-inl.h
@@ -153,6 +153,14 @@
   }
 }
 
+inline mirror::Object* ConcurrentCopying::MarkFromReadBarrier(mirror::Object* from_ref) {
+  // TODO: Consider removing this check when we are done investigating slow paths. b/30162165
+  if (UNLIKELY(mark_from_read_barrier_measurements_)) {
+    return MarkFromReadBarrierWithMeasurements(from_ref);
+  }
+  return Mark(from_ref);
+}
+
 inline mirror::Object* ConcurrentCopying::GetFwdPtr(mirror::Object* from_ref) {
   DCHECK(region_space_->IsInFromSpace(from_ref));
   LockWord lw = from_ref->GetLockWord(false);
diff --git a/runtime/gc/collector/concurrent_copying.cc b/runtime/gc/collector/concurrent_copying.cc
index b7b5aa0..155e032 100644
--- a/runtime/gc/collector/concurrent_copying.cc
+++ b/runtime/gc/collector/concurrent_copying.cc
@@ -17,7 +17,9 @@
 #include "concurrent_copying.h"
 
 #include "art_field-inl.h"
+#include "base/histogram-inl.h"
 #include "base/stl_util.h"
+#include "base/systrace.h"
 #include "debugger.h"
 #include "gc/accounting/heap_bitmap-inl.h"
 #include "gc/accounting/space_bitmap-inl.h"
@@ -39,7 +41,9 @@
 
 static constexpr size_t kDefaultGcMarkStackSize = 2 * MB;
 
-ConcurrentCopying::ConcurrentCopying(Heap* heap, const std::string& name_prefix)
+ConcurrentCopying::ConcurrentCopying(Heap* heap,
+                                     const std::string& name_prefix,
+                                     bool measure_read_barrier_slow_path)
     : GarbageCollector(heap,
                        name_prefix + (name_prefix.empty() ? "" : " ") +
                        "concurrent copying + mark sweep"),
@@ -54,6 +58,14 @@
       heap_mark_bitmap_(nullptr), live_stack_freeze_size_(0), mark_stack_mode_(kMarkStackModeOff),
       weak_ref_access_enabled_(true),
       skipped_blocks_lock_("concurrent copying bytes blocks lock", kMarkSweepMarkStackLock),
+      measure_read_barrier_slow_path_(measure_read_barrier_slow_path),
+      rb_slow_path_ns_(0),
+      rb_slow_path_count_(0),
+      rb_slow_path_count_gc_(0),
+      rb_slow_path_histogram_lock_("Read barrier histogram lock"),
+      rb_slow_path_time_histogram_("Mutator time in read barrier slow path", 500, 32),
+      rb_slow_path_count_total_(0),
+      rb_slow_path_count_gc_total_(0),
       rb_table_(heap_->GetReadBarrierTable()),
       force_evacuate_all_(false),
       immune_gray_stack_lock_("concurrent copying immune gray stack lock",
@@ -162,6 +174,14 @@
     MutexLock mu(Thread::Current(), mark_stack_lock_);
     CHECK(false_gray_stack_.empty());
   }
+
+  mark_from_read_barrier_measurements_ = measure_read_barrier_slow_path_;
+  if (measure_read_barrier_slow_path_) {
+    rb_slow_path_ns_.StoreRelaxed(0);
+    rb_slow_path_count_.StoreRelaxed(0);
+    rb_slow_path_count_gc_.StoreRelaxed(0);
+  }
+
   immune_spaces_.Reset();
   bytes_moved_.StoreRelaxed(0);
   objects_moved_.StoreRelaxed(0);
@@ -1996,9 +2016,17 @@
     MutexLock mu(Thread::Current(), skipped_blocks_lock_);
     skipped_blocks_map_.clear();
   }
-  ReaderMutexLock mu(self, *Locks::mutator_lock_);
-  WriterMutexLock mu2(self, *Locks::heap_bitmap_lock_);
-  heap_->ClearMarkedObjects();
+  {
+    ReaderMutexLock mu(self, *Locks::mutator_lock_);
+    WriterMutexLock mu2(self, *Locks::heap_bitmap_lock_);
+    heap_->ClearMarkedObjects();
+  }
+  if (measure_read_barrier_slow_path_) {
+    MutexLock mu(self, rb_slow_path_histogram_lock_);
+    rb_slow_path_time_histogram_.AdjustAndAddValue(rb_slow_path_ns_.LoadRelaxed());
+    rb_slow_path_count_total_ += rb_slow_path_count_.LoadRelaxed();
+    rb_slow_path_count_gc_total_ += rb_slow_path_count_gc_.LoadRelaxed();
+  }
 }
 
 bool ConcurrentCopying::IsMarkedHeapReference(mirror::HeapReference<mirror::Object>* field) {
@@ -2036,6 +2064,37 @@
   region_space_->RevokeAllThreadLocalBuffers();
 }
 
+mirror::Object* ConcurrentCopying::MarkFromReadBarrierWithMeasurements(mirror::Object* from_ref) {
+  if (Thread::Current() != thread_running_gc_) {
+    rb_slow_path_count_.FetchAndAddRelaxed(1u);
+  } else {
+    rb_slow_path_count_gc_.FetchAndAddRelaxed(1u);
+  }
+  ScopedTrace tr(__FUNCTION__);
+  const uint64_t start_time = measure_read_barrier_slow_path_ ? NanoTime() : 0u;
+  mirror::Object* ret = Mark(from_ref);
+  if (measure_read_barrier_slow_path_) {
+    rb_slow_path_ns_.FetchAndAddRelaxed(NanoTime() - start_time);
+  }
+  return ret;
+}
+
+void ConcurrentCopying::DumpPerformanceInfo(std::ostream& os) {
+  GarbageCollector::DumpPerformanceInfo(os);
+  MutexLock mu(Thread::Current(), rb_slow_path_histogram_lock_);
+  if (rb_slow_path_time_histogram_.SampleSize() > 0) {
+    Histogram<uint64_t>::CumulativeData cumulative_data;
+    rb_slow_path_time_histogram_.CreateHistogram(&cumulative_data);
+    rb_slow_path_time_histogram_.PrintConfidenceIntervals(os, 0.99, cumulative_data);
+  }
+  if (rb_slow_path_count_total_ > 0) {
+    os << "Slow path count " << rb_slow_path_count_total_ << "\n";
+  }
+  if (rb_slow_path_count_gc_total_ > 0) {
+    os << "GC slow path count " << rb_slow_path_count_gc_total_ << "\n";
+  }
+}
+
 }  // namespace collector
 }  // namespace gc
 }  // namespace art
diff --git a/runtime/gc/collector/concurrent_copying.h b/runtime/gc/collector/concurrent_copying.h
index 166a1f0..6a8d052 100644
--- a/runtime/gc/collector/concurrent_copying.h
+++ b/runtime/gc/collector/concurrent_copying.h
@@ -58,17 +58,24 @@
   // Enable verbose mode.
   static constexpr bool kVerboseMode = false;
 
-  ConcurrentCopying(Heap* heap, const std::string& name_prefix = "");
+  ConcurrentCopying(Heap* heap,
+                    const std::string& name_prefix = "",
+                    bool measure_read_barrier_slow_path = false);
   ~ConcurrentCopying();
 
   virtual void RunPhases() OVERRIDE
-      REQUIRES(!mark_stack_lock_, !skipped_blocks_lock_, !immune_gray_stack_lock_);
+      REQUIRES(!immune_gray_stack_lock_,
+               !mark_stack_lock_,
+               !rb_slow_path_histogram_lock_,
+               !skipped_blocks_lock_);
   void InitializePhase() SHARED_REQUIRES(Locks::mutator_lock_)
       REQUIRES(!mark_stack_lock_, !immune_gray_stack_lock_);
   void MarkingPhase() SHARED_REQUIRES(Locks::mutator_lock_)
       REQUIRES(!mark_stack_lock_, !skipped_blocks_lock_, !immune_gray_stack_lock_);
   void ReclaimPhase() SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!mark_stack_lock_);
-  void FinishPhase() REQUIRES(!mark_stack_lock_, !skipped_blocks_lock_);
+  void FinishPhase() REQUIRES(!mark_stack_lock_,
+                              !rb_slow_path_histogram_lock_,
+                              !skipped_blocks_lock_);
 
   void BindBitmaps() SHARED_REQUIRES(Locks::mutator_lock_)
       REQUIRES(!Locks::heap_bitmap_lock_);
@@ -95,7 +102,11 @@
     return IsMarked(ref) == ref;
   }
   template<bool kGrayImmuneObject = true>
-  ALWAYS_INLINE mirror::Object* Mark(mirror::Object* from_ref) SHARED_REQUIRES(Locks::mutator_lock_)
+  ALWAYS_INLINE mirror::Object* Mark(mirror::Object* from_ref)
+      SHARED_REQUIRES(Locks::mutator_lock_)
+      REQUIRES(!mark_stack_lock_, !skipped_blocks_lock_, !immune_gray_stack_lock_);
+  ALWAYS_INLINE mirror::Object* MarkFromReadBarrier(mirror::Object* from_ref)
+      SHARED_REQUIRES(Locks::mutator_lock_)
       REQUIRES(!mark_stack_lock_, !skipped_blocks_lock_, !immune_gray_stack_lock_);
   bool IsMarking() const {
     return is_marking_;
@@ -203,6 +214,10 @@
       REQUIRES(!mark_stack_lock_);
   void ScanImmuneObject(mirror::Object* obj)
       SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!mark_stack_lock_);
+  mirror::Object* MarkFromReadBarrierWithMeasurements(mirror::Object* from_ref)
+      SHARED_REQUIRES(Locks::mutator_lock_)
+      REQUIRES(!mark_stack_lock_, !skipped_blocks_lock_, !immune_gray_stack_lock_);
+  void DumpPerformanceInfo(std::ostream& os) OVERRIDE REQUIRES(!rb_slow_path_histogram_lock_);
 
   space::RegionSpace* region_space_;      // The underlying region space.
   std::unique_ptr<Barrier> gc_barrier_;
@@ -251,6 +266,20 @@
   Atomic<size_t> to_space_bytes_skipped_;
   Atomic<size_t> to_space_objects_skipped_;
 
+  // If measure_read_barrier_slow_path_ is true, we count how long is spent in MarkFromReadBarrier
+  // and also log.
+  bool measure_read_barrier_slow_path_;
+  // mark_from_read_barrier_measurements_ is true if systrace is enabled or
+  // measure_read_barrier_time_ is true.
+  bool mark_from_read_barrier_measurements_;
+  Atomic<uint64_t> rb_slow_path_ns_;
+  Atomic<uint64_t> rb_slow_path_count_;
+  Atomic<uint64_t> rb_slow_path_count_gc_;
+  mutable Mutex rb_slow_path_histogram_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
+  Histogram<uint64_t> rb_slow_path_time_histogram_ GUARDED_BY(rb_slow_path_histogram_lock_);
+  uint64_t rb_slow_path_count_total_ GUARDED_BY(rb_slow_path_histogram_lock_);
+  uint64_t rb_slow_path_count_gc_total_ GUARDED_BY(rb_slow_path_histogram_lock_);
+
   accounting::ReadBarrierTable* rb_table_;
   bool force_evacuate_all_;  // True if all regions are evacuated.
   Atomic<bool> updated_all_immune_objects_;
diff --git a/runtime/gc/collector/garbage_collector.h b/runtime/gc/collector/garbage_collector.h
index 580486a..e0b71a7 100644
--- a/runtime/gc/collector/garbage_collector.h
+++ b/runtime/gc/collector/garbage_collector.h
@@ -181,7 +181,7 @@
   void RecordFree(const ObjectBytePair& freed);
   // Record a free of large objects.
   void RecordFreeLOS(const ObjectBytePair& freed);
-  void DumpPerformanceInfo(std::ostream& os) REQUIRES(!pause_histogram_lock_);
+  virtual void DumpPerformanceInfo(std::ostream& os) REQUIRES(!pause_histogram_lock_);
 
   // Helper functions for querying if objects are marked. These are used for processing references,
   // and will be used for reading system weaks while the GC is running.
diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index a6d62a9..6f4767e 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -157,6 +157,7 @@
            bool verify_pre_sweeping_rosalloc,
            bool verify_post_gc_rosalloc,
            bool gc_stress_mode,
+           bool measure_gc_performance,
            bool use_homogeneous_space_compaction_for_oom,
            uint64_t min_interval_homogeneous_space_compaction_by_oom)
     : non_moving_space_(nullptr),
@@ -599,7 +600,9 @@
       garbage_collectors_.push_back(semi_space_collector_);
     }
     if (MayUseCollector(kCollectorTypeCC)) {
-      concurrent_copying_collector_ = new collector::ConcurrentCopying(this);
+      concurrent_copying_collector_ = new collector::ConcurrentCopying(this,
+                                                                       "",
+                                                                       measure_gc_performance);
       garbage_collectors_.push_back(concurrent_copying_collector_);
     }
     if (MayUseCollector(kCollectorTypeMC)) {
diff --git a/runtime/gc/heap.h b/runtime/gc/heap.h
index 6fb048a..bb0d11a 100644
--- a/runtime/gc/heap.h
+++ b/runtime/gc/heap.h
@@ -182,6 +182,7 @@
        bool verify_pre_sweeping_rosalloc,
        bool verify_post_gc_rosalloc,
        bool gc_stress_mode,
+       bool measure_gc_performance,
        bool use_homogeneous_space_compaction,
        uint64_t min_interval_homogeneous_space_compaction_by_oom);
 
diff --git a/runtime/read_barrier-inl.h b/runtime/read_barrier-inl.h
index 0c3eb3b..92efa21 100644
--- a/runtime/read_barrier-inl.h
+++ b/runtime/read_barrier-inl.h
@@ -220,7 +220,7 @@
 }
 
 inline mirror::Object* ReadBarrier::Mark(mirror::Object* obj) {
-  return Runtime::Current()->GetHeap()->ConcurrentCopyingCollector()->Mark(obj);
+  return Runtime::Current()->GetHeap()->ConcurrentCopyingCollector()->MarkFromReadBarrier(obj);
 }
 
 inline bool ReadBarrier::HasGrayReadBarrierPointer(mirror::Object* obj,
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index 21cd2aa..079c079 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -989,6 +989,7 @@
                        xgc_option.verify_pre_sweeping_rosalloc_,
                        xgc_option.verify_post_gc_rosalloc_,
                        xgc_option.gcstress_,
+                       xgc_option.measure_,
                        runtime_options.GetOrDefault(Opt::EnableHSpaceCompactForOOM),
                        runtime_options.GetOrDefault(Opt::HSpaceCompactForOOMMinIntervalsMs));