6929868: G1: introduce min / max young gen size bounds

Make G1 handle young gen size command line flags more consistently

Reviewed-by: tonyp, jwilhelm

hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -1682,7 +1682,7 @@ bool G1CollectedHeap::expand(size_t expand_bytes) {
       }
       assert(curr == mr.end(), "post-condition");
     }
-    g1_policy()->calculate_reserve(n_regions());
+    g1_policy()->record_new_heap_size(n_regions());
   } else {
     ergo_verbose0(ErgoHeapSizing,
                   "did not expand the heap",
@@ -1733,7 +1733,7 @@ void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
     _expansion_regions += num_regions_deleted;
     update_committed_space(old_end, new_end);
     HeapRegionRemSet::shrink_heap(n_regions());
-    g1_policy()->calculate_reserve(n_regions());
+    g1_policy()->record_new_heap_size(n_regions());
   } else {
     ergo_verbose0(ErgoHeapSizing,
                   "did not shrink the heap",
@@ -3525,6 +3525,19 @@ G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
 
       init_mutator_alloc_region();
 
+      {
+        size_t expand_bytes = g1_policy()->expansion_amount();
+        if (expand_bytes > 0) {
+          size_t bytes_before = capacity();
+          if (!expand(expand_bytes)) {
+            // We failed to expand the heap so let's verify that
+            // committed/uncommitted amount match the backing store
+            assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
+            assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
+          }
+        }
+      }
+
       double end_time_sec = os::elapsedTime();
       double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
       g1_policy()->record_pause_time_ms(pause_time_ms);

hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp

@@ -146,6 +146,7 @@ G1CollectorPolicy::G1CollectorPolicy() :
   _stop_world_start(0.0),
   _all_stop_world_times_ms(new NumberSeq()),
   _all_yield_times_ms(new NumberSeq()),
+  _using_new_ratio_calculations(false),
 
   _all_mod_union_times_ms(new NumberSeq()),
 
@@ -430,7 +431,7 @@ G1CollectorPolicy::G1CollectorPolicy() :
             "it's been updated to %u", reserve_perc);
   }
   _reserve_factor = (double) reserve_perc / 100.0;
-  // This will be set in calculate_reserve() when the heap is expanded
+  // This will be set when the heap is expanded
   // for the first time during initialization.
   _reserve_regions = 0;
 
@@ -458,16 +459,15 @@ void G1CollectorPolicy::initialize_flags() {
 // ParallelScavengeHeap::initialize()). We might change this in the
 // future, but it's a good start.
 class G1YoungGenSizer : public TwoGenerationCollectorPolicy {
-  size_t size_to_region_num(size_t byte_size) {
-    return MAX2((size_t) 1, byte_size / HeapRegion::GrainBytes);
-  }
 
 public:
   G1YoungGenSizer() {
     initialize_flags();
     initialize_size_info();
   }
-
+  size_t size_to_region_num(size_t byte_size) {
+    return MAX2((size_t) 1, byte_size / HeapRegion::GrainBytes);
+  }
   size_t min_young_region_num() {
     return size_to_region_num(_min_gen0_size);
   }
@@ -479,6 +479,13 @@ public:
   }
 };
 
+void G1CollectorPolicy::update_young_list_size_using_newratio(size_t number_of_heap_regions) {
+  assert(number_of_heap_regions > 0, "Heap must be initialized");
+  size_t young_size = number_of_heap_regions / (NewRatio + 1);
+  _min_desired_young_length = young_size;
+  _max_desired_young_length = young_size;
+}
+
 void G1CollectorPolicy::init() {
   // Set aside an initial future to_space.
   _g1 = G1CollectedHeap::heap();
@@ -489,16 +496,35 @@ void G1CollectorPolicy::init() {
 
   G1YoungGenSizer sizer;
   size_t initial_region_num = sizer.initial_young_region_num();
+  _min_desired_young_length = sizer.min_young_region_num();
+  _max_desired_young_length = sizer.max_young_region_num();
 
-  if (UseAdaptiveSizePolicy) {
+  if (FLAG_IS_CMDLINE(NewRatio)) {
-    set_adaptive_young_list_length(true);
+    if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
+      gclog_or_tty->print_cr("-XX:NewSize and -XX:MaxNewSize overrides -XX:NewRatio");
+    } else {
+      // Treat NewRatio as a fixed size that is only recalculated when the heap size changes
+      size_t heap_regions = sizer.size_to_region_num(_g1->n_regions());
+      update_young_list_size_using_newratio(heap_regions);
+      _using_new_ratio_calculations = true;
+    }
+  }
+
+  // GenCollectorPolicy guarantees that min <= initial <= max.
+  // Asserting here just to state that we rely on this property.
+  assert(_min_desired_young_length <= _max_desired_young_length, "Invalid min/max young gen size values");
+  assert(initial_region_num <= _max_desired_young_length, "Initial young gen size too large");
+  assert(_min_desired_young_length <= initial_region_num, "Initial young gen size too small");
+
+  set_adaptive_young_list_length(_min_desired_young_length < _max_desired_young_length);
+  if (adaptive_young_list_length()) {
     _young_list_fixed_length = 0;
   } else {
-    set_adaptive_young_list_length(false);
     _young_list_fixed_length = initial_region_num;
   }
   _free_regions_at_end_of_collection = _g1->free_regions();
   update_young_list_target_length();
+  _prev_eden_capacity = _young_list_target_length * HeapRegion::GrainBytes;
 
   // We may immediately start allocating regions and placing them on the
   // collection set list. Initialize the per-collection set info
@@ -541,11 +567,18 @@ bool G1CollectorPolicy::predict_will_fit(size_t young_length,
   return true;
 }
 
-void G1CollectorPolicy::calculate_reserve(size_t all_regions) {
+void G1CollectorPolicy::record_new_heap_size(size_t new_number_of_regions) {
-  double reserve_regions_d = (double) all_regions * _reserve_factor;
+  // re-calculate the necessary reserve
+  double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
   // We use ceiling so that if reserve_regions_d is > 0.0 (but
   // smaller than 1.0) we'll get 1.
   _reserve_regions = (size_t) ceil(reserve_regions_d);
+
+  if (_using_new_ratio_calculations) {
+    // -XX:NewRatio was specified so we need to update the
+    // young gen length when the heap size has changed.
+    update_young_list_size_using_newratio(new_number_of_regions);
+  }
 }
 
 size_t G1CollectorPolicy::calculate_young_list_desired_min_length(
@@ -561,16 +594,16 @@ size_t G1CollectorPolicy::calculate_young_list_desired_min_length(
       // otherwise we don't have enough info to make the prediction
     }
   }
-  // Here, we might want to also take into account any additional
+  desired_min_length += base_min_length;
-  // constraints (i.e., user-defined minimum bound). Currently, we don't.
+  // make sure we don't go below any user-defined minimum bound
-  return base_min_length + desired_min_length;
+  return MAX2(_min_desired_young_length, desired_min_length);
 }
 
 size_t G1CollectorPolicy::calculate_young_list_desired_max_length() {
   // Here, we might want to also take into account any additional
   // constraints (i.e., user-defined minimum bound). Currently, we
   // effectively don't set this bound.
-  return _g1->n_regions();
+  return _max_desired_young_length;
 }
 
 void G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
@@ -1699,20 +1732,26 @@ void G1CollectorPolicy::print_heap_transition() {
     size_t used_before_gc = _cur_collection_pause_used_at_start_bytes;
     size_t used = _g1->used();
     size_t capacity = _g1->capacity();
+    size_t eden_capacity =
+      (_young_list_target_length * HeapRegion::GrainBytes) - survivor_bytes;
 
     gclog_or_tty->print_cr(
-         "   [Eden: "EXT_SIZE_FORMAT"->"EXT_SIZE_FORMAT" "
+      "   [Eden: "EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT")->"EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT") "
       "Survivors: "EXT_SIZE_FORMAT"->"EXT_SIZE_FORMAT" "
       "Heap: "EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT")->"
       EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT")]",
       EXT_SIZE_PARAMS(_eden_bytes_before_gc),
+      EXT_SIZE_PARAMS(_prev_eden_capacity),
       EXT_SIZE_PARAMS(eden_bytes),
+      EXT_SIZE_PARAMS(eden_capacity),
       EXT_SIZE_PARAMS(_survivor_bytes_before_gc),
       EXT_SIZE_PARAMS(survivor_bytes),
       EXT_SIZE_PARAMS(used_before_gc),
       EXT_SIZE_PARAMS(_capacity_before_gc),
       EXT_SIZE_PARAMS(used),
       EXT_SIZE_PARAMS(capacity));
+
+    _prev_eden_capacity = eden_capacity;
   } else if (PrintGC) {
     _g1->print_size_transition(gclog_or_tty,
                                _cur_collection_pause_used_at_start_bytes,

hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp

@@ -185,6 +185,7 @@ protected:
   bool _adaptive_young_list_length;
   size_t _young_list_target_length;
   size_t _young_list_fixed_length;
+  size_t _prev_eden_capacity; // used for logging
 
   // The max number of regions we can extend the eden by while the GC
   // locker is active. This should be >= _young_list_target_length;
@@ -245,6 +246,10 @@ private:
 
   TruncatedSeq* _max_conc_overhead_seq;
 
+  bool   _using_new_ratio_calculations;
+  size_t _min_desired_young_length; // as set on the command line or default calculations
+  size_t _max_desired_young_length; // as set on the command line or default calculations
+
   size_t _recorded_young_regions;
   size_t _recorded_non_young_regions;
   size_t _recorded_region_num;
@@ -826,9 +831,8 @@ public:
     return _all_pause_times_ms->num() + 1;
   }
 
-  // Recalculate the reserve region number. This should be called
+  // This should be called after the heap is resized.
-  // after the heap is resized.
+  void record_new_heap_size(size_t new_number_of_regions);
-  void calculate_reserve(size_t all_regions);
 
 protected:
 
@@ -841,6 +845,8 @@ protected:
                                                 size_t max_live_bytes);
   void record_concurrent_mark_cleanup_end_work2();
 
+  void update_young_list_size_using_newratio(size_t number_of_heap_regions);
+
 public:
 
   virtual void init();