--- /dev/null	2018-11-30 10:10:44.238550338 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahHeuristics.cpp	2018-11-30 10:22:49.701374478 +0100
@@ -0,0 +1,336 @@
+/*
+ * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
+ *
+ * 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/shared/gcCause.hpp"
+#include "gc/shenandoah/shenandoahBrooksPointer.hpp"
+#include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
+#include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
+#include "gc/shenandoah/shenandoahHeap.inline.hpp"
+#include "gc/shenandoah/shenandoahHeapRegion.hpp"
+#include "gc/shenandoah/shenandoahHeuristics.hpp"
+#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
+#include "logging/log.hpp"
+#include "logging/logTag.hpp"
+
+int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) {
+  if (a._garbage > b._garbage)
+    return -1;
+  else if (a._garbage < b._garbage)
+    return 1;
+  else return 0;
+}
+
+int ShenandoahHeuristics::compare_by_garbage_then_alloc_seq_ascending(RegionData a, RegionData b) {
+  int r = compare_by_garbage(a, b);
+  if (r != 0) {
+    return r;
+  }
+  return compare_by_alloc_seq_ascending(a, b);
+}
+
+int ShenandoahHeuristics::compare_by_alloc_seq_ascending(RegionData a, RegionData b) {
+  if (a._seqnum_last_alloc == b._seqnum_last_alloc)
+    return 0;
+  else if (a._seqnum_last_alloc < b._seqnum_last_alloc)
+    return -1;
+  else return 1;
+}
+
+int ShenandoahHeuristics::compare_by_alloc_seq_descending(RegionData a, RegionData b) {
+  return -compare_by_alloc_seq_ascending(a, b);
+}
+
+ShenandoahHeuristics::ShenandoahHeuristics() :
+  _update_refs_early(false),
+  _update_refs_adaptive(false),
+  _region_data(NULL),
+  _region_data_size(0),
+  _degenerated_cycles_in_a_row(0),
+  _successful_cycles_in_a_row(0),
+  _bytes_in_cset(0),
+  _cycle_start(os::elapsedTime()),
+  _last_cycle_end(0),
+  _gc_times_learned(0),
+  _gc_time_penalties(0),
+  _gc_time_history(new TruncatedSeq(5)),
+  _metaspace_oom()
+{
+  if (strcmp(ShenandoahUpdateRefsEarly, "on") == 0 ||
+      strcmp(ShenandoahUpdateRefsEarly, "true") == 0 ) {
+    _update_refs_early = true;
+  } else if (strcmp(ShenandoahUpdateRefsEarly, "off") == 0 ||
+             strcmp(ShenandoahUpdateRefsEarly, "false") == 0 ) {
+    _update_refs_early = false;
+  } else if (strcmp(ShenandoahUpdateRefsEarly, "adaptive") == 0) {
+    _update_refs_adaptive = true;
+    _update_refs_early = true;
+  } else {
+    vm_exit_during_initialization("Unknown -XX:ShenandoahUpdateRefsEarly option: %s", ShenandoahUpdateRefsEarly);
+  }
+
+  // No unloading during concurrent mark? Communicate that to heuristics
+  if (!ClassUnloadingWithConcurrentMark) {
+    FLAG_SET_DEFAULT(ShenandoahUnloadClassesFrequency, 0);
+  }
+}
+
+ShenandoahHeuristics::~ShenandoahHeuristics() {
+  if (_region_data != NULL) {
+    FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
+  }
+}
+
+ShenandoahHeuristics::RegionData* ShenandoahHeuristics::get_region_data_cache(size_t num) {
+  RegionData* res = _region_data;
+  if (res == NULL) {
+    res = NEW_C_HEAP_ARRAY(RegionData, num, mtGC);
+    _region_data = res;
+    _region_data_size = num;
+  } else if (_region_data_size < num) {
+    res = REALLOC_C_HEAP_ARRAY(RegionData, _region_data, num, mtGC);
+    _region_data = res;
+    _region_data_size = num;
+  }
+  return res;
+}
+
+void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
+  assert(collection_set->count() == 0, "Must be empty");
+
+  ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+  // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.
+
+  size_t num_regions = heap->num_regions();
+
+  RegionData* candidates = get_region_data_cache(num_regions);
+
+  size_t cand_idx = 0;
+
+  size_t total_garbage = 0;
+
+  size_t immediate_garbage = 0;
+  size_t immediate_regions = 0;
+
+  size_t free = 0;
+  size_t free_regions = 0;
+
+  ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
+
+  for (size_t i = 0; i < num_regions; i++) {
+    ShenandoahHeapRegion* region = heap->get_region(i);
+
+    size_t garbage = region->garbage();
+    total_garbage += garbage;
+
+    if (region->is_empty()) {
+      free_regions++;
+      free += ShenandoahHeapRegion::region_size_bytes();
+    } else if (region->is_regular()) {
+      if (!region->has_live()) {
+        // We can recycle it right away and put it in the free set.
+        immediate_regions++;
+        immediate_garbage += garbage;
+        region->make_trash_immediate();
+      } else {
+        // This is our candidate for later consideration.
+        candidates[cand_idx]._region = region;
+        candidates[cand_idx]._garbage = garbage;
+        cand_idx++;
+      }
+    } else if (region->is_humongous_start()) {
+      // Reclaim humongous regions here, and count them as the immediate garbage
+#ifdef ASSERT
+      bool reg_live = region->has_live();
+      bool bm_live = ctx->is_marked(oop(region->bottom() + ShenandoahBrooksPointer::word_size()));
+      assert(reg_live == bm_live,
+             "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
+             BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
+#endif
+      if (!region->has_live()) {
+        heap->trash_humongous_region_at(region);
+
+        // Count only the start. Continuations would be counted on "trash" path
+        immediate_regions++;
+        immediate_garbage += garbage;
+      }
+    } else if (region->is_trash()) {
+      // Count in just trashed collection set, during coalesced CM-with-UR
+      immediate_regions++;
+      immediate_garbage += garbage;
+    }
+  }
+
+  // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
+  // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.
+
+  assert (immediate_garbage <= total_garbage,
+          "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "M vs " SIZE_FORMAT "M",
+          immediate_garbage / M, total_garbage / M);
+
+  size_t immediate_percent = total_garbage == 0 ? 0 : (immediate_garbage * 100 / total_garbage);
+
+  if (immediate_percent <= ShenandoahImmediateThreshold) {
+    choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
+    collection_set->update_region_status();
+
+    size_t cset_percent = total_garbage == 0 ? 0 : (collection_set->garbage() * 100 / total_garbage);
+    log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "M (" SIZE_FORMAT "%% of total), " SIZE_FORMAT "M CSet, " SIZE_FORMAT " CSet regions",
+                       collection_set->garbage() / M, cset_percent, collection_set->live_data() / M, collection_set->count());
+  }
+
+  log_info(gc, ergo)("Immediate Garbage: " SIZE_FORMAT "M (" SIZE_FORMAT "%% of total), " SIZE_FORMAT " regions",
+                     immediate_garbage / M, immediate_percent, immediate_regions);
+}
+
+void ShenandoahHeuristics::record_gc_start() {
+  // Do nothing
+}
+
+void ShenandoahHeuristics::record_gc_end() {
+  // Do nothing
+}
+
+void ShenandoahHeuristics::record_cycle_start() {
+  _cycle_start = os::elapsedTime();
+}
+
+void ShenandoahHeuristics::record_cycle_end() {
+  _last_cycle_end = os::elapsedTime();
+}
+
+void ShenandoahHeuristics::record_phase_time(ShenandoahPhaseTimings::Phase phase, double secs) {
+  // Do nothing
+}
+
+bool ShenandoahHeuristics::should_start_update_refs() {
+  return _update_refs_early;
+}
+
+bool ShenandoahHeuristics::should_start_normal_gc() const {
+  // Perform GC to cleanup metaspace
+  if (has_metaspace_oom()) {
+    // Some of vmTestbase/metaspace tests depend on following line to count GC cycles
+    log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold));
+    return true;
+  }
+
+  double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
+  bool periodic_gc = (last_time_ms > ShenandoahGuaranteedGCInterval);
+  if (periodic_gc) {
+    log_info(gc)("Trigger: Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
+                  last_time_ms, ShenandoahGuaranteedGCInterval);
+  }
+  return periodic_gc;
+}
+
+bool ShenandoahHeuristics::should_start_traversal_gc() {
+  return false;
+}
+
+bool ShenandoahHeuristics::can_do_traversal_gc() {
+  return false;
+}
+
+bool ShenandoahHeuristics::should_degenerate_cycle() {
+  return _degenerated_cycles_in_a_row <= ShenandoahFullGCThreshold;
+}
+
+void ShenandoahHeuristics::record_success_concurrent() {
+  _degenerated_cycles_in_a_row = 0;
+  _successful_cycles_in_a_row++;
+
+  _gc_time_history->add(time_since_last_gc());
+  _gc_times_learned++;
+  _gc_time_penalties -= MIN2<size_t>(_gc_time_penalties, Concurrent_Adjust);
+}
+
+void ShenandoahHeuristics::record_success_degenerated() {
+  _degenerated_cycles_in_a_row++;
+  _successful_cycles_in_a_row = 0;
+  _gc_time_penalties += Degenerated_Penalty;
+}
+
+void ShenandoahHeuristics::record_success_full() {
+  _degenerated_cycles_in_a_row = 0;
+  _successful_cycles_in_a_row++;
+  _gc_time_penalties += Full_Penalty;
+}
+
+void ShenandoahHeuristics::record_allocation_failure_gc() {
+  _bytes_in_cset = 0;
+}
+
+void ShenandoahHeuristics::record_requested_gc() {
+  _bytes_in_cset = 0;
+
+  // Assume users call System.gc() when external state changes significantly,
+  // which forces us to re-learn the GC timings and allocation rates.
+  _gc_times_learned = 0;
+}
+
+bool ShenandoahHeuristics::can_process_references() {
+  if (ShenandoahRefProcFrequency == 0) return false;
+  return true;
+}
+
+bool ShenandoahHeuristics::should_process_references() {
+  if (!can_process_references()) return false;
+  size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter();
+  // Process references every Nth GC cycle.
+  return cycle % ShenandoahRefProcFrequency == 0;
+}
+
+bool ShenandoahHeuristics::can_unload_classes() {
+  if (!ClassUnloading) return false;
+  return true;
+}
+
+bool ShenandoahHeuristics::can_unload_classes_normal() {
+  if (!can_unload_classes()) return false;
+  if (has_metaspace_oom()) return true;
+  if (!ClassUnloadingWithConcurrentMark) return false;
+  if (ShenandoahUnloadClassesFrequency == 0) return false;
+  return true;
+}
+
+bool ShenandoahHeuristics::should_unload_classes() {
+  if (!can_unload_classes_normal()) return false;
+  if (has_metaspace_oom()) return true;
+  size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter();
+  // Unload classes every Nth GC cycle.
+  // This should not happen in the same cycle as process_references to amortize costs.
+  // Offsetting by one is enough to break the rendezvous when periods are equal.
+  // When periods are not equal, offsetting by one is just as good as any other guess.
+  return (cycle + 1) % ShenandoahUnloadClassesFrequency == 0;
+}
+
+void ShenandoahHeuristics::initialize() {
+  // Nothing to do by default.
+}
+
+double ShenandoahHeuristics::time_since_last_gc() const {
+  return os::elapsedTime() - _cycle_start;
+}