src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp

@@ -419,7 +419,7 @@ bool ShenandoahAdaptiveHeuristics::should_start_gc() {
   //     ShenandoahControlIntervalMax.  The current control interval (or the max control interval) should also be added into
   //     the calculation of avg_cycle_time below.
 
-  double avg_cycle_time = _gc_time_history->davg() + (_margin_of_error_sd * _gc_time_history->dsd());
+  double avg_cycle_time = _gc_cycle_time_history->davg() + (_margin_of_error_sd * _gc_cycle_time_history->dsd());
 
   size_t last_live_memory = get_last_live_memory();
   size_t penultimate_live_memory = get_penultimate_live_memory();

src/hotspot/share/gc/shenandoah/heuristics/shenandoahHeuristics.cpp

@@ -57,7 +57,7 @@ ShenandoahHeuristics::ShenandoahHeuristics(ShenandoahGeneration* generation) :
   _last_cycle_end(0),
   _gc_times_learned(0),
   _gc_time_penalties(0),
-  _gc_time_history(new TruncatedSeq(10, ShenandoahAdaptiveDecayFactor)),
+  _gc_cycle_time_history(new TruncatedSeq(10, ShenandoahAdaptiveDecayFactor)),
   _live_memory_last_cycle(0),
   _live_memory_penultimate_cycle(0),
   _metaspace_oom()
@@ -302,7 +302,7 @@ void ShenandoahHeuristics::record_success_concurrent(bool abbreviated) {
   _successful_cycles_in_a_row++;
 
   if (!(abbreviated && ShenandoahAdaptiveIgnoreShortCycles)) {
-    _gc_time_history->add(time_since_last_gc());
+    _gc_cycle_time_history->add(elapsed_cycle_time());
     _gc_times_learned++;
   }
 
@@ -361,7 +361,7 @@ void ShenandoahHeuristics::initialize() {
   // Nothing to do by default.
 }
 
-double ShenandoahHeuristics::time_since_last_gc() const {
+double ShenandoahHeuristics::elapsed_cycle_time() const {
   return os::elapsedTime() - _cycle_start;
 }
 

src/hotspot/share/gc/shenandoah/heuristics/shenandoahHeuristics.hpp

@@ -97,7 +97,7 @@ class ShenandoahHeuristics : public CHeapObj<mtGC> {
 
   size_t _gc_times_learned;
   intx _gc_time_penalties;
-  TruncatedSeq* _gc_time_history;
+  TruncatedSeq* _gc_cycle_time_history;
 
   size_t _live_memory_last_cycle;
   size_t _live_memory_penultimate_cycle;
@@ -168,7 +168,7 @@ class ShenandoahHeuristics : public CHeapObj<mtGC> {
   virtual bool is_experimental() = 0;
   virtual void initialize();
 
-  double time_since_last_gc() const;
+  double elapsed_cycle_time() const;
 
   void save_last_live_memory(size_t live_memory);
   size_t get_last_live_memory();

src/hotspot/share/gc/shenandoah/mode/shenandoahGenerationalMode.cpp

@@ -36,6 +36,7 @@ void ShenandoahGenerationalMode::initialize_flags() const {
     FLAG_SET_DEFAULT(VerifyBeforeExit, false);
   }
 
+  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(GCTimeRatio, 70);
   SHENANDOAH_ERGO_OVERRIDE_DEFAULT(NewRatio, 1);
   SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUnloadClassesFrequency, 0);
   SHENANDOAH_ERGO_ENABLE_FLAG(ExplicitGCInvokesConcurrent);

src/hotspot/share/gc/shenandoah/shenandoahArguments.cpp

@@ -69,6 +69,13 @@ void ShenandoahArguments::initialize() {
     FLAG_SET_DEFAULT(UseNUMA, true);
   }
 
+  // We use this as the time period for tracking minimum mutator utilization (MMU).
+  // In generational mode, the MMU is used as a signal to adjust the size of the
+  // young generation.
+  if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
+    FLAG_SET_DEFAULT(GCPauseIntervalMillis, 5000);
+  }
+
   // Set up default number of concurrent threads. We want to have cycles complete fast
   // enough, but we also do not want to steal too much CPU from the concurrently running
   // application. Using 1/4 of available threads for concurrent GC seems a good

src/hotspot/share/gc/shenandoah/shenandoahAsserts.hpp

@@ -167,6 +167,9 @@ class ShenandoahAsserts {
 
 #define shenandoah_assert_heaplocked_or_fullgc_safepoint() \
                     ShenandoahAsserts::assert_heaplocked_or_fullgc_safepoint(__FILE__, __LINE__)
+
+#define shenandoah_assert_generational() \
+                    assert(ShenandoahHeap::heap()->mode()->is_generational(), "Must be in generational mode here.")
 #else
 #define shenandoah_assert_in_heap(interior_loc, obj)
 #define shenandoah_assert_in_heap_or_null(interior_loc, obj)
@@ -218,6 +221,7 @@ class ShenandoahAsserts {
 #define shenandoah_assert_not_heaplocked()
 #define shenandoah_assert_heaplocked_or_safepoint()
 #define shenandoah_assert_heaplocked_or_fullgc_safepoint()
+#define shenandoah_assert_generational()
 
 #endif
 

src/hotspot/share/gc/shenandoah/shenandoahCollectorPolicy.hpp

@@ -52,14 +52,12 @@ class ShenandoahCollectorPolicy : public CHeapObj<mtGC> {
   size_t _explicit_full;
   size_t _implicit_concurrent;
   size_t _implicit_full;
+  size_t _cycle_counter;
   size_t _degen_points[ShenandoahGC::_DEGENERATED_LIMIT];
 
   ShenandoahSharedFlag _in_shutdown;
-
   ShenandoahTracer* _tracer;
 
-  size_t _cycle_counter;
-
 public:
   ShenandoahCollectorPolicy();
 

src/hotspot/share/gc/shenandoah/shenandoahConcurrentGC.cpp

@@ -1202,6 +1202,7 @@ void ShenandoahConcurrentGC::op_final_updaterefs() {
   }
 
   heap->rebuild_free_set(true /*concurrent*/);
+  heap->adjust_generation_sizes();
 }
 
 void ShenandoahConcurrentGC::op_final_roots() {

src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp

@@ -448,7 +448,7 @@ void ShenandoahControlThread::process_phase_timings(const ShenandoahHeap* heap)
 //
 void ShenandoahControlThread::service_concurrent_normal_cycle(
   const ShenandoahHeap* heap, const GenerationMode generation, GCCause::Cause cause) {
-
+  GCIdMark gc_id_mark;
   switch (generation) {
     case YOUNG: {
       // Run a young cycle. This might or might not, have interrupted an ongoing
@@ -458,32 +458,29 @@ void ShenandoahControlThread::service_concurrent_normal_cycle(
       // that are in the cset.
       log_info(gc, ergo)("Start GC cycle (YOUNG)");
       service_concurrent_cycle(heap->young_generation(), cause, false);
-      heap->young_generation()->log_status();
       break;
     }
     case GLOBAL: {
       log_info(gc, ergo)("Start GC cycle (GLOBAL)");
       service_concurrent_cycle(heap->global_generation(), cause, false);
-      heap->global_generation()->log_status();
       break;
     }
     case OLD: {
       log_info(gc, ergo)("Start GC cycle (OLD)");
       service_concurrent_old_cycle(heap, cause);
-      heap->old_generation()->log_status();
       break;
     }
     default:
       ShouldNotReachHere();
   }
+  log_heap_status(heap);
 }
 
 void ShenandoahControlThread::service_concurrent_old_cycle(const ShenandoahHeap* heap, GCCause::Cause &cause) {
 
   ShenandoahOldGeneration* old_generation = heap->old_generation();
   ShenandoahYoungGeneration* young_generation = heap->young_generation();
 
-  GCIdMark gc_id_mark;
   TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
 
   switch (old_generation->state()) {
@@ -582,6 +579,15 @@ bool ShenandoahControlThread::resume_concurrent_old_cycle(ShenandoahGeneration*
   return true;
 }
 
+void ShenandoahControlThread::log_heap_status(const ShenandoahHeap* heap) {
+  if (heap->mode()->is_generational()) {
+    heap->young_generation()->log_status();
+    heap->old_generation()->log_status();
+  } else {
+    heap->global_generation()->log_status();
+  }
+}
+
 bool ShenandoahControlThread::check_soft_max_changed() const {
   ShenandoahHeap* heap = ShenandoahHeap::heap();
   size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
@@ -640,7 +646,6 @@ void ShenandoahControlThread::service_concurrent_cycle(ShenandoahGeneration* gen
   if (check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle)) return;
 
   ShenandoahHeap* heap = ShenandoahHeap::heap();
-  GCIdMark gc_id_mark;
   ShenandoahGCSession session(cause, generation);
   TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
 

src/hotspot/share/gc/shenandoah/shenandoahControlThread.hpp

@@ -189,6 +189,8 @@ class ShenandoahControlThread: public ConcurrentGCThread {
 
   void service_concurrent_cycle(const ShenandoahHeap* heap, ShenandoahGeneration* generation, GCCause::Cause &cause,
                                 bool do_old_gc_bootstrap);
+
+  void log_heap_status(const ShenandoahHeap* heap);
 };
 
 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHCONTROLTHREAD_HPP

src/hotspot/share/gc/shenandoah/shenandoahDegeneratedGC.cpp

@@ -296,6 +296,8 @@ void ShenandoahDegenGC::op_degenerated() {
     heap->set_old_evac_reserve(0);
     heap->reset_old_evac_expended();
     heap->set_promoted_reserve(0);
+
+    heap->adjust_generation_sizes();
   }
 
   if (ShenandoahVerify) {

src/hotspot/share/gc/shenandoah/shenandoahFullGC.cpp

@@ -336,6 +336,8 @@ void ShenandoahFullGC::do_it(GCCause::Cause gc_cause) {
   // Resize metaspace
   MetaspaceGC::compute_new_size();
 
+  heap->adjust_generation_sizes();
+
   // Free worker slices
   for (uint i = 0; i < heap->max_workers(); i++) {
     delete worker_slices[i];

src/hotspot/share/gc/shenandoah/shenandoahGeneration.cpp

@@ -988,6 +988,19 @@ size_t ShenandoahGeneration::adjusted_unaffiliated_regions() const {
   return (adjusted_capacity() - used_regions_size()) / ShenandoahHeapRegion::region_size_bytes();
 }
 
+
+void ShenandoahGeneration::increase_capacity(size_t increment) {
+  shenandoah_assert_heaplocked_or_safepoint();
+  _max_capacity += increment;
+  _soft_max_capacity += increment;
+}
+
+void ShenandoahGeneration::decrease_capacity(size_t decrement) {
+  shenandoah_assert_heaplocked_or_safepoint();
+  _max_capacity -= decrement;
+  _soft_max_capacity -= decrement;
+}
+
 void ShenandoahGeneration::record_success_concurrent(bool abbreviated) {
   heuristics()->record_success_concurrent(abbreviated);
   ShenandoahHeap::heap()->shenandoah_policy()->record_success_concurrent();
@@ -997,3 +1010,14 @@ void ShenandoahGeneration::record_success_degenerated() {
   heuristics()->record_success_degenerated();
   ShenandoahHeap::heap()->shenandoah_policy()->record_success_degenerated();
 }
+
+void ShenandoahGeneration::add_collection_time(double time_seconds) {
+  _collection_thread_time_s += time_seconds;
+}
+
+double ShenandoahGeneration::reset_collection_time() {
+  double t = _collection_thread_time_s;
+  _collection_thread_time_s = 0.0;
+  return t;
+}
+

src/hotspot/share/gc/shenandoah/shenandoahGeneration.hpp

@@ -46,6 +46,8 @@ class ShenandoahGeneration : public CHeapObj<mtGC> {
 
   ShenandoahReferenceProcessor* const _ref_processor;
 
+  double _collection_thread_time_s;
+
 protected:
   // Usage
   size_t _affiliated_region_count;
@@ -109,6 +111,9 @@ class ShenandoahGeneration : public CHeapObj<mtGC> {
   void reset_bytes_allocated_since_gc_start();
   void increase_allocated(size_t bytes);
 
+  void increase_capacity(size_t increment);
+  void decrease_capacity(size_t decrement);
+
   void set_soft_max_capacity(size_t soft_max_capacity) {
     _soft_max_capacity = soft_max_capacity;
   }
@@ -181,6 +186,9 @@ class ShenandoahGeneration : public CHeapObj<mtGC> {
 
   virtual void record_success_concurrent(bool abbreviated);
   virtual void record_success_degenerated();
+
+  virtual void add_collection_time(double time_seconds);
+  double reset_collection_time();
 };
 
 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHGENERATION_HPP

src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp

@@ -625,6 +625,8 @@ class ShenandoahInitWorkerGCLABClosure : public ThreadClosure {
 
 void ShenandoahHeap::post_initialize() {
   CollectedHeap::post_initialize();
+  _mmu_tracker.initialize();
+
   MutexLocker ml(Threads_lock);
 
   ShenandoahInitWorkerGCLABClosure init_gclabs;
@@ -1093,6 +1095,13 @@ void ShenandoahHeap::coalesce_and_fill_old_regions() {
   parallel_heap_region_iterate(&coalesce);
 }
 
+bool ShenandoahHeap::adjust_generation_sizes() {
+  if (mode()->is_generational()) {
+    return _mmu_tracker.adjust_generation_sizes();
+  }
+  return false;
+}
+
 HeapWord* ShenandoahHeap::allocate_new_tlab(size_t min_size,
                                             size_t requested_size,
                                             size_t* actual_size) {
@@ -1741,6 +1750,7 @@ void ShenandoahHeap::prepare_for_verify() {
 
 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
   tcl->do_thread(_control_thread);
+  tcl->do_thread(_regulator_thread);
   workers()->threads_do(tcl);
   if (_safepoint_workers != NULL) {
     _safepoint_workers->threads_do(tcl);
@@ -1772,6 +1782,33 @@ void ShenandoahHeap::print_tracing_info() const {
   }
 }
 
+void ShenandoahHeap::on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation) {
+  set_gc_cause(cause);
+  set_gc_generation(generation);
+
+  shenandoah_policy()->record_cycle_start();
+  generation->heuristics()->record_cycle_start();
+
+  // When a cycle starts, attribute any thread activity when the collector
+  // is idle to the global generation.
+  _mmu_tracker.record(global_generation());
+}
+
+void ShenandoahHeap::on_cycle_end(ShenandoahGeneration* generation) {
+  generation->heuristics()->record_cycle_end();
+
+  if (mode()->is_generational() &&
+      ((generation->generation_mode() == GLOBAL) || upgraded_to_full())) {
+    // If we just completed a GLOBAL GC, claim credit for completion of young-gen and old-gen GC as well
+    young_generation()->heuristics()->record_cycle_end();
+    old_generation()->heuristics()->record_cycle_end();
+  }
+  set_gc_cause(GCCause::_no_gc);
+
+  // When a cycle ends, the thread activity is attributed to the respective generation
+  _mmu_tracker.record(generation);
+}
+
 void ShenandoahHeap::verify(VerifyOption vo) {
   if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
     if (ShenandoahVerify) {

src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp

@@ -34,6 +34,7 @@
 #include "gc/shenandoah/shenandoahLock.hpp"
 #include "gc/shenandoah/shenandoahEvacOOMHandler.hpp"
 #include "gc/shenandoah/shenandoahEvacTracker.hpp"
+#include "gc/shenandoah/shenandoahMmuTracker.hpp"
 #include "gc/shenandoah/shenandoahPadding.hpp"
 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
 #include "gc/shenandoah/shenandoahUnload.hpp"
@@ -535,6 +536,7 @@ class ShenandoahHeap : public CollectedHeap {
 
   ShenandoahPhaseTimings*       _phase_timings;
   ShenandoahEvacuationTracker*  _evac_tracker;
+  ShenandoahMmuTracker          _mmu_tracker;
 
   ShenandoahControlThread*   control_thread()          { return _control_thread;    }
   ShenandoahRegulatorThread* regulator_thread()        { return _regulator_thread;  }
@@ -553,6 +555,9 @@ class ShenandoahHeap : public CollectedHeap {
   ShenandoahPhaseTimings*      phase_timings()   const { return _phase_timings;     }
   ShenandoahEvacuationTracker* evac_tracker()    const { return  _evac_tracker;     }
 
+  void on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation);
+  void on_cycle_end(ShenandoahGeneration* generation);
+
   ShenandoahVerifier*        verifier();
 
 // ---------- VM subsystem bindings
@@ -817,6 +822,7 @@ class ShenandoahHeap : public CollectedHeap {
   void cancel_old_gc();
   bool is_old_gc_active();
   void coalesce_and_fill_old_regions();
+  bool adjust_generation_sizes();
 
 // ---------- Helper functions
 //