--- a/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp	Wed Nov 25 11:34:16 2015 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp	Tue Nov 24 10:22:36 2015 +0100
@@ -402,6 +402,11 @@
   return new_obj;
 }
 
+size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
+  assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
+  return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
+}
+
 // If could fit into free regions w/o expansion, try.
 // Otherwise, if can expand, do so.
 // Otherwise, if using ex regions might help, try with ex given back.
@@ -411,7 +416,7 @@
   verify_region_sets_optional();
 
   uint first = G1_NO_HRM_INDEX;
-  uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
+  uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 
   if (obj_regions == 1) {
     // Only one region to allocate, try to use a fast path by directly allocating
@@ -1011,6 +1016,8 @@
       // collection hoping that there's enough space in the heap.
       result = humongous_obj_allocate(word_size, AllocationContext::current());
       if (result != NULL) {
+        size_t size_in_regions = humongous_obj_size_in_regions(word_size);
+        g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
         return result;
       }
 
@@ -5234,6 +5241,8 @@
 }
 
 void G1CollectedHeap::record_obj_copy_mem_stats() {
+  g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
+
   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
                                                create_g1_evac_summary(&_old_evac_stats));
 }
@@ -5618,6 +5627,14 @@
         cur->set_young_index_in_cset(-1);
       }
       cur->set_evacuation_failed(false);
+      // When moving a young gen region to old gen, we "allocate" that whole region
+      // there. This is in addition to any already evacuated objects. Notify the
+      // policy about that.
+      // Old gen regions do not cause an additional allocation: both the objects
+      // still in the region and the ones already moved are accounted for elsewhere.
+      if (cur->is_young()) {
+        policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes);
+      }
       // The region is now considered to be old.
       cur->set_old();
       // Do some allocation statistics accounting. Regions that failed evacuation

--- a/hotspot/src/share/vm/gc/g1/g1CollectedHeap.hpp	Wed Nov 25 11:34:16 2015 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1CollectedHeap.hpp	Tue Nov 24 10:22:36 2015 +0100
@@ -1343,6 +1343,10 @@
     return (region_size / 2);
   }
 
+  // Returns the number of regions the humongous object of the given word size
+  // requires.
+  static size_t humongous_obj_size_in_regions(size_t word_size);
+
   // Print the maximum heap capacity.
   virtual size_t max_capacity() const;
 

--- a/hotspot/src/share/vm/gc/g1/g1CollectorPolicy.cpp	Wed Nov 25 11:34:16 2015 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1CollectorPolicy.cpp	Tue Nov 24 10:22:36 2015 +0100
@@ -28,6 +28,7 @@
 #include "gc/g1/concurrentMarkThread.inline.hpp"
 #include "gc/g1/g1CollectedHeap.inline.hpp"
 #include "gc/g1/g1CollectorPolicy.hpp"
+#include "gc/g1/g1IHOPControl.hpp"
 #include "gc/g1/g1ErgoVerbose.hpp"
 #include "gc/g1/g1GCPhaseTimes.hpp"
 #include "gc/g1/g1Log.hpp"
@@ -38,6 +39,7 @@
 #include "runtime/java.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "utilities/debug.hpp"
+#include "utilities/pair.hpp"
 
 // Different defaults for different number of GC threads
 // They were chosen by running GCOld and SPECjbb on debris with different
@@ -148,7 +150,11 @@
   _recorded_survivor_tail(NULL),
   _survivors_age_table(true),
 
-  _gc_overhead_perc(0.0) {
+  _gc_overhead_perc(0.0),
+
+  _bytes_allocated_in_old_since_last_gc(0),
+  _ihop_control(NULL),
+  _initial_mark_to_mixed() {
 
   // SurvRateGroups below must be initialized after the predictor because they
   // indirectly use it through this object passed to their constructor.
@@ -288,6 +294,10 @@
   _collectionSetChooser = new CollectionSetChooser();
 }
 
+G1CollectorPolicy::~G1CollectorPolicy() {
+  delete _ihop_control;
+}
+
 double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const {
   return _predictor.get_new_prediction(seq);
 }
@@ -317,6 +327,8 @@
   if (max_young_size != MaxNewSize) {
     FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
   }
+
+  _ihop_control = create_ihop_control();
 }
 
 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
@@ -522,25 +534,26 @@
   return _young_gen_sizer->max_desired_young_length();
 }
 
-void G1CollectorPolicy::update_young_list_max_and_target_length() {
-  update_young_list_max_and_target_length(get_new_prediction(_rs_lengths_seq));
+uint G1CollectorPolicy::update_young_list_max_and_target_length() {
+  return update_young_list_max_and_target_length(get_new_prediction(_rs_lengths_seq));
 }
 
-void G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
-  update_young_list_target_length(rs_lengths);
+uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
+  uint unbounded_target_length = update_young_list_target_length(rs_lengths);
   update_max_gc_locker_expansion();
+  return unbounded_target_length;
 }
 
-void G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
-  _young_list_target_length = bounded_young_list_target_length(rs_lengths);
+uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
+  YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
+  _young_list_target_length = young_lengths.first;
+  return young_lengths.second;
 }
 
-void G1CollectorPolicy::update_young_list_target_length() {
-  update_young_list_target_length(get_new_prediction(_rs_lengths_seq));
-}
+G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
+  YoungTargetLengths result;
 
-uint G1CollectorPolicy::bounded_young_list_target_length(size_t rs_lengths) const {
-  // Calculate the absolute and desired min bounds.
+  // Calculate the absolute and desired min bounds first.
 
   // This is how many young regions we already have (currently: the survivors).
   uint base_min_length = recorded_survivor_regions();
@@ -552,15 +565,7 @@
   desired_min_length = MAX2(desired_min_length, absolute_min_length);
   // Calculate the absolute and desired max bounds.
 
-  // We will try our best not to "eat" into the reserve.
-  uint absolute_max_length = 0;
-  if (_free_regions_at_end_of_collection > _reserve_regions) {
-    absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
-  }
   uint desired_max_length = calculate_young_list_desired_max_length();
-  if (desired_max_length > absolute_max_length) {
-    desired_max_length = absolute_max_length;
-  }
 
   uint young_list_target_length = 0;
   if (adaptive_young_list_length()) {
@@ -581,6 +586,17 @@
     young_list_target_length = _young_list_fixed_length;
   }
 
+  result.second = young_list_target_length;
+
+  // We will try our best not to "eat" into the reserve.
+  uint absolute_max_length = 0;
+  if (_free_regions_at_end_of_collection > _reserve_regions) {
+    absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
+  }
+  if (desired_max_length > absolute_max_length) {
+    desired_max_length = absolute_max_length;
+  }
+
   // Make sure we don't go over the desired max length, nor under the
   // desired min length. In case they clash, desired_min_length wins
   // which is why that test is second.
@@ -595,7 +611,8 @@
          "we should be able to allocate at least one eden region");
   assert(young_list_target_length >= absolute_min_length, "post-condition");
 
-  return young_list_target_length;
+  result.first = young_list_target_length;
+  return result;
 }
 
 uint
@@ -838,6 +855,10 @@
   update_young_list_max_and_target_length();
   update_rs_lengths_prediction();
   _collectionSetChooser->clear();
+
+  _bytes_allocated_in_old_since_last_gc = 0;
+
+  record_pause(FullGC, _full_collection_start_sec, end_sec);
 }
 
 void G1CollectorPolicy::record_stop_world_start() {
@@ -895,7 +916,7 @@
   _cur_mark_stop_world_time_ms += elapsed_time_ms;
   _prev_collection_pause_end_ms += elapsed_time_ms;
 
-  _mmu_tracker->add_pause(_mark_remark_start_sec, end_time_sec);
+  record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 }
 
 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
@@ -906,6 +927,10 @@
   bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
                                                               "skip last young-only gc");
   collector_state()->set_last_young_gc(should_continue_with_reclaim);
+  // We skip the marking phase.
+  if (!should_continue_with_reclaim) {
+    abort_time_to_mixed_tracking();
+  }
   collector_state()->set_in_marking_window(false);
 }
 
@@ -952,12 +977,13 @@
     return false;
   }
 
-  size_t marking_initiating_used_threshold =
-    (_g1->capacity() / 100) * InitiatingHeapOccupancyPercent;
+  size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
+
   size_t cur_used_bytes = _g1->non_young_capacity_bytes();
   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
+  size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 
-  if ((cur_used_bytes + alloc_byte_size) > marking_initiating_used_threshold) {
+  if (marking_request_bytes > marking_initiating_used_threshold) {
     if (collector_state()->gcs_are_young() && !collector_state()->last_young_gc()) {
       ergo_verbose5(ErgoConcCycles,
         "request concurrent cycle initiation",
@@ -969,7 +995,7 @@
         cur_used_bytes,
         alloc_byte_size,
         marking_initiating_used_threshold,
-        (double) InitiatingHeapOccupancyPercent,
+        (double) marking_initiating_used_threshold / _g1->capacity() * 100,
         source);
       return true;
     } else {
@@ -996,10 +1022,7 @@
 
 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned) {
   double end_time_sec = os::elapsedTime();
-  assert(_cur_collection_pause_used_regions_at_start >= cset_region_length(),
-         "otherwise, the subtraction below does not make sense");
-  size_t rs_size =
-            _cur_collection_pause_used_regions_at_start - cset_region_length();
+
   size_t cur_used_bytes = _g1->used();
   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
   bool last_pause_included_initial_mark = false;
@@ -1013,6 +1036,8 @@
   }
 #endif // PRODUCT
 
+  record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
+
   last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
   if (last_pause_included_initial_mark) {
     record_concurrent_mark_init_end(0.0);
@@ -1020,19 +1045,16 @@
     maybe_start_marking();
   }
 
-  _mmu_tracker->add_pause(end_time_sec - pause_time_ms/1000.0, end_time_sec);
+  double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
+  if (app_time_ms < MIN_TIMER_GRANULARITY) {
+    // This usually happens due to the timer not having the required
+    // granularity. Some Linuxes are the usual culprits.
+    // We'll just set it to something (arbitrarily) small.
+    app_time_ms = 1.0;
+  }
 
   if (update_stats) {
     _trace_young_gen_time_data.record_end_collection(pause_time_ms, phase_times());
-    // this is where we update the allocation rate of the application
-    double app_time_ms =
-      (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
-    if (app_time_ms < MIN_TIMER_GRANULARITY) {
-      // This usually happens due to the timer not having the required
-      // granularity. Some Linuxes are the usual culprits.
-      // We'll just set it to something (arbitrarily) small.
-      app_time_ms = 1.0;
-    }
     // We maintain the invariant that all objects allocated by mutator
     // threads will be allocated out of eden regions. So, we can use
     // the eden region number allocated since the previous GC to
@@ -1077,6 +1099,9 @@
     if (next_gc_should_be_mixed("start mixed GCs",
                                 "do not start mixed GCs")) {
       collector_state()->set_gcs_are_young(false);
+    } else {
+      // We aborted the mixed GC phase early.
+      abort_time_to_mixed_tracking();
     }
 
     collector_state()->set_last_young_gc(false);
@@ -1085,7 +1110,6 @@
   if (!collector_state()->last_gc_was_young()) {
     // This is a mixed GC. Here we decide whether to continue doing
     // mixed GCs or not.
-
     if (!next_gc_should_be_mixed("continue mixed GCs",
                                  "do not continue mixed GCs")) {
       collector_state()->set_gcs_are_young(true);
@@ -1177,9 +1201,18 @@
   collector_state()->set_in_marking_window(new_in_marking_window);
   collector_state()->set_in_marking_window_im(new_in_marking_window_im);
   _free_regions_at_end_of_collection = _g1->num_free_regions();
-  update_young_list_max_and_target_length();
+  // IHOP control wants to know the expected young gen length if it were not
+  // restrained by the heap reserve. Using the actual length would make the
+  // prediction too small and the limit the young gen every time we get to the
+  // predicted target occupancy.
+  size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
   update_rs_lengths_prediction();
 
+  update_ihop_prediction(app_time_ms / 1000.0,
+                         _bytes_allocated_in_old_since_last_gc,
+                         last_unrestrained_young_length * HeapRegion::GrainBytes);
+  _bytes_allocated_in_old_since_last_gc = 0;
+
   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
 
@@ -1205,6 +1238,53 @@
   _collectionSetChooser->verify();
 }
 
+G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
+  return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent,
+                                 G1CollectedHeap::heap()->max_capacity());
+}
+
+void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s,
+                                               size_t mutator_alloc_bytes,
+                                               size_t young_gen_size) {
+  // Always try to update IHOP prediction. Even evacuation failures give information
+  // about e.g. whether to start IHOP earlier next time.
+
+  // Avoid using really small application times that might create samples with
+  // very high or very low values. They may be caused by e.g. back-to-back gcs.
+  double const min_valid_time = 1e-6;
+
+  bool report = false;
+
+  double marking_to_mixed_time = -1.0;
+  if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
+    marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
+    assert(marking_to_mixed_time > 0.0,
+           "Initial mark to mixed time must be larger than zero but is %.3f",
+           marking_to_mixed_time);
+    if (marking_to_mixed_time > min_valid_time) {
+      _ihop_control->update_marking_length(marking_to_mixed_time);
+      report = true;
+    }
+  }
+
+  // As an approximation for the young gc promotion rates during marking we use
+  // all of them. In many applications there are only a few if any young gcs during
+  // marking, which makes any prediction useless. This increases the accuracy of the
+  // prediction.
+  if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
+    _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
+    report = true;
+  }
+
+  if (report) {
+    report_ihop_statistics();
+  }
+}
+
+void G1CollectorPolicy::report_ihop_statistics() {
+  _ihop_control->print();
+}
+
 #define EXT_SIZE_FORMAT "%.1f%s"
 #define EXT_SIZE_PARAMS(bytes)                                  \
   byte_size_in_proper_unit((double)(bytes)),                    \
@@ -1216,7 +1296,6 @@
   _survivor_used_bytes_before_gc = young_list->survivor_used_bytes();
   _heap_capacity_bytes_before_gc = _g1->capacity();
   _heap_used_bytes_before_gc = _g1->used();
-  _cur_collection_pause_used_regions_at_start = _g1->num_used_regions();
 
   _eden_capacity_bytes_before_gc =
          (_young_list_target_length * HeapRegion::GrainBytes) - _survivor_used_bytes_before_gc;
@@ -1717,8 +1796,7 @@
   return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
 }
 
-void
-G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
+void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
   _collectionSetChooser->clear();
 
   WorkGang* workers = _g1->workers();
@@ -1737,7 +1815,8 @@
   _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
   _cur_mark_stop_world_time_ms += elapsed_time_ms;
   _prev_collection_pause_end_ms += elapsed_time_ms;
-  _mmu_tracker->add_pause(_mark_cleanup_start_sec, end_sec);
+
+  record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
 }
 
 // Add the heap region at the head of the non-incremental collection set
@@ -1953,6 +2032,59 @@
   }
 }
 
+G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
+  assert(!collector_state()->full_collection(), "must be");
+  if (collector_state()->during_initial_mark_pause()) {
+    assert(collector_state()->last_gc_was_young(), "must be");
+    assert(!collector_state()->last_young_gc(), "must be");
+    return InitialMarkGC;
+  } else if (collector_state()->last_young_gc()) {
+    assert(!collector_state()->during_initial_mark_pause(), "must be");
+    assert(collector_state()->last_gc_was_young(), "must be");
+    return LastYoungGC;
+  } else if (!collector_state()->last_gc_was_young()) {
+    assert(!collector_state()->during_initial_mark_pause(), "must be");
+    assert(!collector_state()->last_young_gc(), "must be");
+    return MixedGC;
+  } else {
+    assert(collector_state()->last_gc_was_young(), "must be");
+    assert(!collector_state()->during_initial_mark_pause(), "must be");
+    assert(!collector_state()->last_young_gc(), "must be");
+    return YoungOnlyGC;
+  }
+}
+
+void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
+  // Manage the MMU tracker. For some reason it ignores Full GCs.
+  if (kind != FullGC) {
+    _mmu_tracker->add_pause(start, end);
+  }
+  // Manage the mutator time tracking from initial mark to first mixed gc.
+  switch (kind) {
+    case FullGC:
+      abort_time_to_mixed_tracking();
+      break;
+    case Cleanup:
+    case Remark:
+    case YoungOnlyGC:
+    case LastYoungGC:
+      _initial_mark_to_mixed.add_pause(end - start);
+      break;
+    case InitialMarkGC:
+      _initial_mark_to_mixed.record_initial_mark_end(end);
+      break;
+    case MixedGC:
+      _initial_mark_to_mixed.record_mixed_gc_start(start);
+      break;
+    default:
+      ShouldNotReachHere();
+  }
+}
+
+void G1CollectorPolicy::abort_time_to_mixed_tracking() {
+  _initial_mark_to_mixed.reset();
+}
+
 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
                                                 const char* false_action_str) const {
   CollectionSetChooser* cset_chooser = _collectionSetChooser;

--- a/hotspot/src/share/vm/gc/g1/g1CollectorPolicy.hpp	Wed Nov 25 11:34:16 2015 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1CollectorPolicy.hpp	Tue Nov 24 10:22:36 2015 +0100
@@ -29,9 +29,11 @@
 #include "gc/g1/g1CollectorState.hpp"
 #include "gc/g1/g1GCPhaseTimes.hpp"
 #include "gc/g1/g1InCSetState.hpp"
+#include "gc/g1/g1InitialMarkToMixedTimeTracker.hpp"
 #include "gc/g1/g1MMUTracker.hpp"
 #include "gc/g1/g1Predictions.hpp"
 #include "gc/shared/collectorPolicy.hpp"
+#include "utilities/pair.hpp"
 
 // A G1CollectorPolicy makes policy decisions that determine the
 // characteristics of the collector.  Examples include:
@@ -40,6 +42,7 @@
 
 class HeapRegion;
 class CollectionSetChooser;
+class G1IHOPControl;
 
 // TraceYoungGenTime collects data on _both_ young and mixed evacuation pauses
 // (the latter may contain non-young regions - i.e. regions that are
@@ -163,6 +166,15 @@
 
 class G1CollectorPolicy: public CollectorPolicy {
  private:
+  G1IHOPControl* _ihop_control;
+
+  G1IHOPControl* create_ihop_control() const;
+  // Update the IHOP control with necessary statistics.
+  void update_ihop_prediction(double mutator_time_s,
+                              size_t mutator_alloc_bytes,
+                              size_t young_gen_size);
+  void report_ihop_statistics();
+
   G1Predictions _predictor;
 
   double get_new_prediction(TruncatedSeq const* seq) const;
@@ -182,7 +194,6 @@
   CollectionSetChooser* _collectionSetChooser;
 
   double _full_collection_start_sec;
-  uint   _cur_collection_pause_used_regions_at_start;
 
   // These exclude marking times.
   TruncatedSeq* _recent_gc_times_ms;
@@ -271,9 +282,17 @@
 
   size_t _pending_cards;
 
+  // The amount of allocated bytes in old gen during the last mutator and the following
+  // young GC phase.
+  size_t _bytes_allocated_in_old_since_last_gc;
+
+  G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
 public:
   const G1Predictions& predictor() const { return _predictor; }
 
+  // Add the given number of bytes to the total number of allocated bytes in the old gen.
+  void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
+
   // Accessors
 
   void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
@@ -473,16 +492,18 @@
   double _mark_remark_start_sec;
   double _mark_cleanup_start_sec;
 
-  void update_young_list_max_and_target_length();
-  void update_young_list_max_and_target_length(size_t rs_lengths);
+  // Updates the internal young list maximum and target lengths. Returns the
+  // unbounded young list target length.
+  uint update_young_list_max_and_target_length();
+  uint update_young_list_max_and_target_length(size_t rs_lengths);
 
   // Update the young list target length either by setting it to the
   // desired fixed value or by calculating it using G1's pause
   // prediction model. If no rs_lengths parameter is passed, predict
   // the RS lengths using the prediction model, otherwise use the
   // given rs_lengths as the prediction.
-  void update_young_list_target_length();
-  void update_young_list_target_length(size_t rs_lengths);
+  // Returns the unbounded young list target length.
+  uint update_young_list_target_length(size_t rs_lengths);
 
   // Calculate and return the minimum desired young list target
   // length. This is the minimum desired young list length according
@@ -505,7 +526,10 @@
                                           uint desired_min_length,
                                           uint desired_max_length) const;
 
-  uint bounded_young_list_target_length(size_t rs_lengths) const;
+  // Result of the bounded_young_list_target_length() method, containing both the
+  // bounded as well as the unbounded young list target lengths in this order.
+  typedef Pair<uint, uint, StackObj> YoungTargetLengths;
+  YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
 
   void update_rs_lengths_prediction();
   void update_rs_lengths_prediction(size_t prediction);
@@ -536,10 +560,30 @@
 
   // Sets up marking if proper conditions are met.
   void maybe_start_marking();
+
+  // The kind of STW pause.
+  enum PauseKind {
+    FullGC,
+    YoungOnlyGC,
+    MixedGC,
+    LastYoungGC,
+    InitialMarkGC,
+    Cleanup,
+    Remark
+  };
+
+  // Calculate PauseKind from internal state.
+  PauseKind young_gc_pause_kind() const;
+  // Record the given STW pause with the given start and end times (in s).
+  void record_pause(PauseKind kind, double start, double end);
+  // Indicate that we aborted marking before doing any mixed GCs.
+  void abort_time_to_mixed_tracking();
 public:
 
   G1CollectorPolicy();
 
+  virtual ~G1CollectorPolicy();
+
   virtual G1CollectorPolicy* as_g1_policy() { return this; }
 
   G1CollectorState* collector_state() const;

--- a/hotspot/src/share/vm/gc/g1/g1ErgoVerbose.cpp	Wed Nov 25 11:34:16 2015 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1ErgoVerbose.cpp	Tue Nov 24 10:22:36 2015 +0100
@@ -57,6 +57,7 @@
   case ErgoConcCycles:        return "Concurrent Cycles";
   case ErgoMixedGCs:          return "Mixed GCs";
   case ErgoTiming:            return "Timing";
+  case ErgoIHOP:              return "IHOP";
   default:
     ShouldNotReachHere();
     // Keep the Windows compiler happy

--- a/hotspot/src/share/vm/gc/g1/g1ErgoVerbose.hpp	Wed Nov 25 11:34:16 2015 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1ErgoVerbose.hpp	Tue Nov 24 10:22:36 2015 +0100
@@ -71,6 +71,7 @@
   ErgoConcCycles,
   ErgoMixedGCs,
   ErgoTiming,
+  ErgoIHOP,
 
   ErgoHeuristicNum
 } ErgoHeuristic;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/g1IHOPControl.cpp	Tue Nov 24 10:22:36 2015 +0100
@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc/g1/g1CollectedHeap.inline.hpp"
+#include "gc/g1/g1ErgoVerbose.hpp"
+#include "gc/g1/g1IHOPControl.hpp"
+
+G1IHOPControl::G1IHOPControl(double initial_ihop_percent, size_t target_occupancy) :
+  _initial_ihop_percent(initial_ihop_percent),
+  _target_occupancy(target_occupancy),
+  _last_allocated_bytes(0),
+  _last_allocation_time_s(0.0)
+{
+  assert(_initial_ihop_percent >= 0.0 && _initial_ihop_percent <= 100.0, "Initial IHOP value must be between 0 and 100 but is %.3f", initial_ihop_percent);
+}
+
+void G1IHOPControl::update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size) {
+  assert(allocation_time_s >= 0.0, "Allocation time must be positive but is %.3f", allocation_time_s);
+
+  _last_allocation_time_s = allocation_time_s;
+  _last_allocated_bytes = allocated_bytes;
+}
+
+void G1IHOPControl::print() {
+  size_t cur_conc_mark_start_threshold = get_conc_mark_start_threshold();
+  ergo_verbose6(ErgoIHOP,
+                "basic information",
+                ergo_format_reason("value update")
+                ergo_format_byte_perc("threshold")
+                ergo_format_byte("target occupancy")
+                ergo_format_byte("current occupancy")
+                ergo_format_double("recent old gen allocation rate")
+                ergo_format_double("recent marking phase length"),
+                cur_conc_mark_start_threshold,
+                cur_conc_mark_start_threshold * 100.0 / _target_occupancy,
+                _target_occupancy,
+                G1CollectedHeap::heap()->used(),
+                _last_allocation_time_s > 0.0 ? _last_allocated_bytes / _last_allocation_time_s : 0.0,
+                last_marking_length_s());
+}
+
+G1StaticIHOPControl::G1StaticIHOPControl(double ihop_percent, size_t target_occupancy) :
+  G1IHOPControl(ihop_percent, target_occupancy),
+  _last_marking_length_s(0.0) {
+  assert(_target_occupancy > 0, "Target occupancy must be larger than zero.");
+}
+
+#ifndef PRODUCT
+static void test_update(G1IHOPControl* ctrl, double alloc_time, size_t alloc_amount, size_t young_size, double mark_time) {
+  for (int i = 0; i < 100; i++) {
+    ctrl->update_allocation_info(alloc_time, alloc_amount, young_size);
+    ctrl->update_marking_length(mark_time);
+  }
+}
+
+void G1StaticIHOPControl::test() {
+  size_t const initial_ihop = 45;
+
+  G1StaticIHOPControl ctrl(initial_ihop, 100);
+
+  size_t threshold = ctrl.get_conc_mark_start_threshold();
+  assert(threshold == initial_ihop,
+         "Expected IHOP threshold of " SIZE_FORMAT " but is " SIZE_FORMAT, initial_ihop, threshold);
+
+  ctrl.update_allocation_info(100.0, 100, 100);
+  threshold = ctrl.get_conc_mark_start_threshold();
+  assert(threshold == initial_ihop,
+         "Expected IHOP threshold of " SIZE_FORMAT " but is " SIZE_FORMAT, initial_ihop, threshold);
+
+  ctrl.update_marking_length(1000.0);
+  threshold = ctrl.get_conc_mark_start_threshold();
+  assert(threshold == initial_ihop,
+         "Expected IHOP threshold of " SIZE_FORMAT " but is " SIZE_FORMAT, initial_ihop, threshold);
+
+  // Whatever we pass, the IHOP value must stay the same.
+  test_update(&ctrl, 2, 10, 10, 3);
+  threshold = ctrl.get_conc_mark_start_threshold();
+  assert(threshold == initial_ihop,
+         "Expected IHOP threshold of " SIZE_FORMAT " but is " SIZE_FORMAT, initial_ihop, threshold);
+
+  test_update(&ctrl, 12, 10, 10, 3);
+  threshold = ctrl.get_conc_mark_start_threshold();
+  assert(threshold == initial_ihop,
+         "Expected IHOP threshold of " SIZE_FORMAT " but is " SIZE_FORMAT, initial_ihop, threshold);
+}
+
+void IHOP_test() {
+  G1StaticIHOPControl::test();
+}
+#endif

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/g1IHOPControl.hpp	Tue Nov 24 10:22:36 2015 +0100
@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_G1_G1IHOPCONTROL_HPP
+#define SHARE_VM_GC_G1_G1IHOPCONTROL_HPP
+
+#include "memory/allocation.hpp"
+
+// Base class for algorithms that calculate the heap occupancy at which
+// concurrent marking should start. This heap usage threshold should be relative
+// to old gen size.
+class G1IHOPControl : public CHeapObj<mtGC> {
+ protected:
+  // The initial IHOP value relative to the target occupancy.
+  double _initial_ihop_percent;
+  // The target maximum occupancy of the heap.
+  size_t _target_occupancy;
+
+  // Most recent complete mutator allocation period in seconds.
+  double _last_allocation_time_s;
+  // Amount of bytes allocated during _last_allocation_time_s.
+  size_t _last_allocated_bytes;
+
+  // Initialize an instance with the initial IHOP value in percent and the target
+  // occupancy. The target occupancy is the number of bytes when marking should
+  // be finished and reclaim started.
+  G1IHOPControl(double initial_ihop_percent, size_t target_occupancy);
+
+  // Most recent time from the end of the initial mark to the start of the first
+  // mixed gc.
+  virtual double last_marking_length_s() const = 0;
+ public:
+  virtual ~G1IHOPControl() { }
+
+  // Get the current non-young occupancy at which concurrent marking should start.
+  virtual size_t get_conc_mark_start_threshold() = 0;
+
+  // Update information about time during which allocations in the Java heap occurred,
+  // how large these allocations were in bytes, and an additional buffer.
+  // The allocations should contain any amount of space made unusable for further
+  // allocation, e.g. any waste caused by TLAB allocation, space at the end of
+  // humongous objects that can not be used for allocation, etc.
+  // Together with the target occupancy, this additional buffer should contain the
+  // difference between old gen size and total heap size at the start of reclamation,
+  // and space required for that reclamation.
+  virtual void update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size);
+  // Update the time spent in the mutator beginning from the end of initial mark to
+  // the first mixed gc.
+  virtual void update_marking_length(double marking_length_s) = 0;
+
+  virtual void print();
+};
+
+// The returned concurrent mark starting occupancy threshold is a fixed value
+// relative to the maximum heap size.
+class G1StaticIHOPControl : public G1IHOPControl {
+  // Most recent mutator time between the end of initial mark to the start of the
+  // first mixed gc.
+  double _last_marking_length_s;
+ protected:
+  double last_marking_length_s() const { return _last_marking_length_s; }
+ public:
+  G1StaticIHOPControl(double ihop_percent, size_t target_occupancy);
+
+  size_t get_conc_mark_start_threshold() { return (size_t) (_initial_ihop_percent * _target_occupancy / 100.0); }
+
+  virtual void update_marking_length(double marking_length_s) {
+   assert(marking_length_s > 0.0, "Marking length must be larger than zero but is %.3f", marking_length_s);
+    _last_marking_length_s = marking_length_s;
+  }
+
+#ifndef PRODUCT
+  static void test();
+#endif
+};
+
+#endif // SHARE_VM_GC_G1_G1IHOPCONTROL_HPP

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/g1InitialMarkToMixedTimeTracker.hpp	Tue Nov 24 10:22:36 2015 +0100
@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_G1_G1INITIALMARKTOMIXEDTIMETRACKER_HPP
+#define SHARE_VM_GC_G1_G1INITIALMARKTOMIXEDTIMETRACKER_HPP
+
+#include "utilities/globalDefinitions.hpp"
+#include "utilities/debug.hpp"
+
+// Used to track time from the end of initial mark to the first mixed GC.
+// After calling the initial mark/mixed gc notifications, the result can be
+// obtained in last_marking_time() once, after which the tracking resets.
+// Any pauses recorded by add_pause() will be subtracted from that results.
+class G1InitialMarkToMixedTimeTracker VALUE_OBJ_CLASS_SPEC {
+private:
+  bool _active;
+  double _initial_mark_end_time;
+  double _mixed_start_time;
+  double _total_pause_time;
+
+  double wall_time() const {
+    return _mixed_start_time - _initial_mark_end_time;
+  }
+public:
+  G1InitialMarkToMixedTimeTracker() { reset(); }
+
+  // Record initial mark pause end, starting the time tracking.
+  void record_initial_mark_end(double end_time) {
+    assert(!_active, "Initial mark out of order.");
+    _initial_mark_end_time = end_time;
+    _active = true;
+  }
+
+  // Record the first mixed gc pause start, ending the time tracking.
+  void record_mixed_gc_start(double start_time) {
+    if (_active) {
+      _mixed_start_time = start_time;
+      _active = false;
+    }
+  }
+
+  double last_marking_time() {
+    assert(has_result(), "Do not have all measurements yet.");
+    double result = (_mixed_start_time - _initial_mark_end_time) - _total_pause_time;
+    reset();
+    return result;
+  }
+
+  void reset() {
+    _active = false;
+    _total_pause_time = 0.0;
+    _initial_mark_end_time = -1.0;
+    _mixed_start_time = -1.0;
+  }
+
+  void add_pause(double time) {
+    if (_active) {
+      _total_pause_time += time;
+    }
+  }
+
+  // Returns whether we have a result that can be retrieved.
+  bool has_result() const { return _mixed_start_time > 0.0 && _initial_mark_end_time > 0.0; }
+};
+
+#endif // SHARE_VM_GC_G1_G1INITIALMARKTOMIXEDTIMETRACKER_HPP

--- a/hotspot/src/share/vm/prims/jni.cpp	Wed Nov 25 11:34:16 2015 +0100
+++ b/hotspot/src/share/vm/prims/jni.cpp	Tue Nov 24 10:22:36 2015 +0100
@@ -3889,6 +3889,7 @@
 void TestBufferingOopClosure_test();
 void TestCodeCacheRemSet_test();
 void FreeRegionList_test();
+void IHOP_test();
 void test_memset_with_concurrent_readers();
 void TestPredictions_test();
 void WorkerDataArray_test();
@@ -3937,6 +3938,7 @@
     run_unit_test(TestCodeCacheRemSet_test());
     if (UseG1GC) {
       run_unit_test(FreeRegionList_test());
+      run_unit_test(IHOP_test());
     }
     run_unit_test(test_memset_with_concurrent_readers());
     run_unit_test(TestPredictions_test());