--- /dev/null	2020-01-17 11:46:19.065201212 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahMetrics.cpp	2020-01-17 17:10:20.724129894 +0100
@@ -0,0 +1,179 @@
+/*
+ * Copyright (c) 2013, 2019, 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/shenandoahMetrics.hpp"
+#include "gc/shenandoah/shenandoahHeap.inline.hpp"
+#include "gc/shenandoah/shenandoahHeapRegion.hpp"
+#include "gc/shenandoah/shenandoahFreeSet.hpp"
+
+/*
+ * Internal fragmentation metric: describes how fragmented the heap regions are.
+ *
+ * It is derived as:
+ *
+ *               sum(used[i]^2, i=0..k)
+ *   IF = 1 - ------------------------------
+ *              C * sum(used[i], i=0..k)
+ *
+ * ...where k is the number of regions in computation, C is the region capacity, and
+ * used[i] is the used space in the region.
+ *
+ * The non-linearity causes IF to be lower for the cases where the same total heap
+ * used is densely packed. For example:
+ *   a) Heap is completely full  => IF = 0
+ *   b) Heap is half full, first 50% regions are completely full => IF = 0
+ *   c) Heap is half full, each region is 50% full => IF = 1/2
+ *   d) Heap is quarter full, first 50% regions are completely full => IF = 0
+ *   e) Heap is quarter full, each region is 25% full => IF = 3/4
+ *   f) Heap has the small object per each region => IF =~ 1
+ */
+double ShenandoahMetrics::internal_fragmentation() {
+  ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+  double squared = 0;
+  double linear = 0;
+  int count = 0;
+  for (size_t c = 0; c < heap->num_regions(); c++) {
+    ShenandoahHeapRegion* r = heap->get_region(c);
+    size_t used = r->used();
+    squared += used * used;
+    linear += used;
+    count++;
+  }
+
+  if (count > 0) {
+    double s = squared / (ShenandoahHeapRegion::region_size_bytes() * linear);
+    return 1 - s;
+  } else {
+    return 0;
+  }
+}
+
+/*
+ * External fragmentation metric: describes how fragmented the heap is.
+ *
+ * It is derived as:
+ *
+ *   EF = 1 - largest_contiguous_free / total_free
+ *
+ * For example:
+ *   a) Heap is completely empty => EF = 0
+ *   b) Heap is completely full => EF = 1
+ *   c) Heap is first-half full => EF = 1/2
+ *   d) Heap is half full, full and empty regions interleave => EF =~ 1
+ */
+double ShenandoahMetrics::external_fragmentation() {
+  ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+  size_t last_idx = 0;
+  size_t max_contig = 0;
+  size_t empty_contig = 0;
+
+  size_t free = 0;
+  for (size_t c = 0; c < heap->num_regions(); c++) {
+    ShenandoahHeapRegion* r = heap->get_region(c);
+
+    if (r->is_empty() && (last_idx + 1 == c)) {
+      empty_contig++;
+    } else {
+      empty_contig = 0;
+    }
+
+    free += r->free();
+    max_contig = MAX2(max_contig, empty_contig);
+    last_idx = c;
+  }
+
+  if (free > 0) {
+    return 1 - (1.0 * max_contig * ShenandoahHeapRegion::region_size_bytes() / free);
+  } else {
+    return 1;
+  }
+}
+
+ShenandoahMetricsSnapshot::ShenandoahMetricsSnapshot() {
+  _heap = ShenandoahHeap::heap();
+}
+
+void ShenandoahMetricsSnapshot::snap_before() {
+  _used_before = _heap->used();
+  _if_before = ShenandoahMetrics::internal_fragmentation();
+  _ef_before = ShenandoahMetrics::external_fragmentation();
+}
+void ShenandoahMetricsSnapshot::snap_after() {
+  _used_after = _heap->used();
+  _if_after = ShenandoahMetrics::internal_fragmentation();
+  _ef_after = ShenandoahMetrics::external_fragmentation();
+}
+
+bool ShenandoahMetricsSnapshot::is_good_progress() {
+  // Under the critical threshold?
+  size_t free_actual   = _heap->free_set()->available();
+  size_t free_expected = _heap->max_capacity() / 100 * ShenandoahCriticalFreeThreshold;
+  bool prog_free = free_actual >= free_expected;
+  log_info(gc, ergo)("%s progress for free space: " SIZE_FORMAT "%s, need " SIZE_FORMAT "%s",
+                     prog_free ? "Good" : "Bad",
+                     byte_size_in_proper_unit(free_actual),   proper_unit_for_byte_size(free_actual),
+                     byte_size_in_proper_unit(free_expected), proper_unit_for_byte_size(free_expected));
+  if (!prog_free) {
+    return false;
+  }
+
+  // Freed up enough?
+  size_t progress_actual   = (_used_before > _used_after) ? _used_before - _used_after : 0;
+  size_t progress_expected = ShenandoahHeapRegion::region_size_bytes();
+  bool prog_used = progress_actual >= progress_expected;
+  log_info(gc, ergo)("%s progress for used space: " SIZE_FORMAT "%s, need " SIZE_FORMAT "%s",
+                     prog_used ? "Good" : "Bad",
+                     byte_size_in_proper_unit(progress_actual),   proper_unit_for_byte_size(progress_actual),
+                     byte_size_in_proper_unit(progress_expected), proper_unit_for_byte_size(progress_expected));
+  if (prog_used) {
+    return true;
+  }
+
+  // Internal fragmentation is down?
+  double if_actual = _if_before - _if_after;
+  double if_expected = 0.01; // 1% should be enough
+  bool prog_if = if_actual >= if_expected;
+  log_info(gc, ergo)("%s progress for internal fragmentation: %.1f%%, need %.1f%%",
+                     prog_if ? "Good" : "Bad",
+                     if_actual * 100, if_expected * 100);
+  if (prog_if) {
+    return true;
+  }
+
+  // External fragmentation is down?
+  double ef_actual = _ef_before - _ef_after;
+  double ef_expected = 0.01; // 1% should be enough
+  bool prog_ef = ef_actual >= ef_expected;
+  log_info(gc, ergo)("%s progress for external fragmentation: %.1f%%, need %.1f%%",
+                     prog_ef ? "Good" : "Bad",
+                     ef_actual * 100, ef_expected * 100);
+  if (prog_ef) {
+    return true;
+  }
+
+  // Nothing good had happened.
+  return false;
+}