--- /dev/null	2020-02-06 11:34:07.664987501 +0100
+++ new/src/hotspot/share/gc/shenandoah/heuristics/shenandoahCompactHeuristics.cpp	2020-02-06 19:19:17.745543821 +0100
@@ -0,0 +1,112 @@
+/*
+ * 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/shenandoah/shenandoahCollectionSet.hpp"
+#include "gc/shenandoah/heuristics/shenandoahCompactHeuristics.hpp"
+#include "gc/shenandoah/shenandoahFreeSet.hpp"
+#include "gc/shenandoah/shenandoahHeapRegion.hpp"
+#include "logging/log.hpp"
+#include "logging/logTag.hpp"
+
+ShenandoahCompactHeuristics::ShenandoahCompactHeuristics() : ShenandoahHeuristics() {
+  SHENANDOAH_ERGO_ENABLE_FLAG(ExplicitGCInvokesConcurrent);
+  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahImplicitGCInvokesConcurrent);
+  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahUncommit);
+  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahAlwaysClearSoftRefs);
+  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahAllocationThreshold,  10);
+  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahImmediateThreshold,   100);
+  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUncommitDelay,        1000);
+  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahGuaranteedGCInterval, 30000);
+  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahGarbageThreshold,     10);
+
+  // Final configuration checks
+  SHENANDOAH_CHECK_FLAG_SET(ShenandoahLoadRefBarrier);
+  SHENANDOAH_CHECK_FLAG_SET(ShenandoahSATBBarrier);
+  SHENANDOAH_CHECK_FLAG_SET(ShenandoahKeepAliveBarrier);
+  SHENANDOAH_CHECK_FLAG_SET(ShenandoahCASBarrier);
+  SHENANDOAH_CHECK_FLAG_SET(ShenandoahCloneBarrier);
+}
+
+bool ShenandoahCompactHeuristics::should_start_gc() const {
+  ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+  size_t capacity = heap->max_capacity();
+  size_t available = heap->free_set()->available();
+
+  size_t threshold_bytes_allocated = capacity / 100 * ShenandoahAllocationThreshold;
+  size_t min_threshold = capacity / 100 * ShenandoahMinFreeThreshold;
+
+  if (available < min_threshold) {
+    log_info(gc)("Trigger: Free (" SIZE_FORMAT "%s) is below minimum threshold (" SIZE_FORMAT "%s)",
+                 byte_size_in_proper_unit(available),     proper_unit_for_byte_size(available),
+                 byte_size_in_proper_unit(min_threshold), proper_unit_for_byte_size(min_threshold));
+    return true;
+  }
+
+  size_t bytes_allocated = heap->bytes_allocated_since_gc_start();
+  if (bytes_allocated > threshold_bytes_allocated) {
+    log_info(gc)("Trigger: Allocated since last cycle (" SIZE_FORMAT "%s) is larger than allocation threshold (" SIZE_FORMAT "%s)",
+                 byte_size_in_proper_unit(bytes_allocated),           proper_unit_for_byte_size(bytes_allocated),
+                 byte_size_in_proper_unit(threshold_bytes_allocated), proper_unit_for_byte_size(threshold_bytes_allocated));
+    return true;
+  }
+
+  return ShenandoahHeuristics::should_start_gc();
+}
+
+void ShenandoahCompactHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
+                                                                        RegionData* data, size_t size,
+                                                                        size_t actual_free) {
+  // Do not select too large CSet that would overflow the available free space
+  size_t max_cset = actual_free * 3 / 4;
+
+  log_info(gc, ergo)("CSet Selection. Actual Free: " SIZE_FORMAT "%s, Max CSet: " SIZE_FORMAT "%s",
+                     byte_size_in_proper_unit(actual_free), proper_unit_for_byte_size(actual_free),
+                     byte_size_in_proper_unit(max_cset),    proper_unit_for_byte_size(max_cset));
+
+  size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;
+
+  size_t live_cset = 0;
+  for (size_t idx = 0; idx < size; idx++) {
+    ShenandoahHeapRegion* r = data[idx]._region;
+    size_t new_cset = live_cset + r->get_live_data_bytes();
+    if (new_cset < max_cset && r->garbage() > threshold) {
+      live_cset = new_cset;
+      cset->add_region(r);
+    }
+  }
+}
+
+const char* ShenandoahCompactHeuristics::name() {
+  return "compact";
+}
+
+bool ShenandoahCompactHeuristics::is_diagnostic() {
+  return false;
+}
+
+bool ShenandoahCompactHeuristics::is_experimental() {
+  return false;
+}