diff -r 714474295e0a -r b537e6386306 test/hotspot/gtest/metaspace/test_leftOverBins.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/gtest/metaspace/test_leftOverBins.cpp	Fri Nov 01 10:28:15 2019 +0100
@@ -0,0 +1,282 @@
+/*
+ * Copyright (c) 2019, SAP SE. All rights reserved.
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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"
+
+//#define LOG_PLEASE
+
+#include "metaspaceTestsCommon.hpp"
+
+class LeftOverBinsTest {
+
+  // A simple preallocated buffer used to "feed" the allocator.
+  // Mimicks chunk retirement leftover blocks.
+  class FeederBuffer {
+
+    static const size_t buf_word_size = 512 * K;
+    MetaWord* _buf;
+    size_t _used;
+
+  public:
+
+    FeederBuffer() : _used(0) {
+      _buf = NEW_C_HEAP_ARRAY(MetaWord, buf_word_size, mtInternal);
+    }
+
+    ~FeederBuffer() {
+      FREE_C_HEAP_ARRAY(MetaWord, _buf);
+    }
+
+    MetaWord* get(size_t word_size) {
+      if (_used > (buf_word_size - word_size)) {
+        return NULL;
+      }
+      MetaWord* p = _buf + _used;
+      _used += word_size;
+      return p;
+    }
+
+  };
+
+  FeederBuffer _fb;
+  LeftOverManager _lom;
+
+  // random generator for block feeding
+  RandSizeGenerator _rgen_feeding;
+
+  // random generator for allocations (and, hence, deallocations)
+  RandSizeGenerator _rgen_allocations;
+
+  SizeCounter _allocated_words;
+
+  struct allocation_t {
+    allocation_t* next;
+    size_t word_size;
+    MetaWord* p;
+  };
+
+  // Array of the same size as the pool max capacity; holds the allocated elements.
+  allocation_t* _allocations;
+
+
+  int _num_allocs;
+  int _num_deallocs;
+  int _num_feeds;
+
+  bool feed_some() {
+    size_t word_size = _rgen_feeding.get();
+    MetaWord* p = _fb.get(word_size);
+    if (p != NULL) {
+      _lom.add_block(p, word_size);
+      return true;
+    }
+    return false;
+  }
+
+  void deallocate_top() {
+
+    allocation_t* a = _allocations;
+    if (a != NULL) {
+      _allocations = a->next;
+      check_marked_range(a->p, a->word_size);
+      _lom.add_block(a->p, a->word_size);
+      delete a;
+      DEBUG_ONLY(_lom.verify();)
+    }
+  }
+
+  bool allocate() {
+
+    size_t word_size = MAX2(_rgen_allocations.get(), _lom.minimal_word_size());
+    MetaWord* p = _lom.get_block(word_size);
+    if (p != NULL) {
+      _allocated_words.increment_by(word_size);
+      allocation_t* a = new allocation_t;
+      a->p = p; a->word_size = word_size;
+      a->next = _allocations;
+      _allocations = a;
+      DEBUG_ONLY(_lom.verify();)
+      mark_range(p, word_size);
+      return true;
+    }
+    return false;
+  }
+
+  void test_all_marked_ranges() {
+    for (allocation_t* a = _allocations; a != NULL; a = a->next) {
+      check_marked_range(a->p, a->word_size);
+    }
+  }
+
+  void test_loop() {
+    // We loop and in each iteration execute one of three operations:
+    // - allocation from lom
+    // - deallocation to lom of a previously allocated block
+    // - feeding a new larger block into the lom (mimicks chunk retiring)
+    // When we have fed all large blocks into the lom (feedbuffer empty), we
+    //  switch to draining the lom completely (only allocs)
+    bool forcefeed = false;
+    bool draining = false;
+    bool stop = false;
+    int iter = 100000; // safety stop
+    while (!stop && iter > 0) {
+      iter --;
+      int surprise = (int)os::random() % 10;
+      if (!draining && (surprise >= 7 || forcefeed)) {
+        forcefeed = false;
+        if (feed_some()) {
+          _num_feeds ++;
+        } else {
+          // We fed all input memory into the LOM. Now lets proceed until the lom is drained.
+          draining = true;
+        }
+      } else if (!draining && surprise < 1) {
+        deallocate_top();
+        _num_deallocs ++;
+      } else {
+        if (allocate()) {
+          _num_allocs ++;
+        } else {
+          if (draining) {
+            stop = _lom.total_word_size() < 512;
+          } else {
+            forcefeed = true;
+          }
+        }
+      }
+      if ((iter % 1000) == 0) {
+        DEBUG_ONLY(_lom.verify();)
+        test_all_marked_ranges();
+        LOG("a %d (" SIZE_FORMAT "), d %d, f %d", _num_allocs, _allocated_words.get(), _num_deallocs, _num_feeds);
+#ifdef LOG_PLEASE
+        _lom.print(tty, true);
+        tty->cr();
+#endif
+      }
+    }
+
+    // Drain
+
+
+  }
+
+
+
+public:
+
+  LeftOverBinsTest(size_t avg_alloc_size) :
+    _fb(), _lom(),
+    _rgen_feeding(128, 4096),
+    _rgen_allocations(avg_alloc_size / 4, avg_alloc_size * 2, 0.01f, avg_alloc_size / 3, avg_alloc_size * 30),
+    _allocations(NULL),
+    _num_allocs(0), _num_deallocs(0), _num_feeds(0)
+  {
+    // some initial feeding
+    _lom.add_block(_fb.get(1024), 1024);
+  }
+
+
+  static void test_small_allocations() {
+    LeftOverBinsTest test(10);
+    test.test_loop();
+  }
+
+  static void test_medium_allocations() {
+    LeftOverBinsTest test(30);
+    test.test_loop();
+  }
+
+  static void test_large_allocations() {
+    LeftOverBinsTest test(150);
+    test.test_loop();
+  }
+
+
+};
+
+TEST_VM(metaspace, leftoverbins_mask_basic) {
+  // Basic tests
+  metaspace::BinMap map;
+  EXPECT_TRUE(map.all_zero());
+  for (int i = 0; i < map.size(); i ++) {
+    map.set_bit(i);
+    EXPECT_TRUE(map.get_bit(i));
+    map.clr_bit(i);
+    EXPECT_FALSE(map.get_bit(i));
+    EXPECT_TRUE(map.all_zero());
+  }
+}
+
+TEST_VM(metaspace, leftoverbins_mask_find_next_set_bit) {
+  metaspace::BinMap map;
+  EXPECT_TRUE(map.all_zero());
+  for (int i = 0; i < map.size(); i ++) {
+    map.set_bit(i);
+    for (int j = 0; j < i; j ++) {
+      int n = map.find_next_set_bit(j);
+      if (j <= i) {
+        EXPECT_EQ(n, i);
+      } else {
+        EXPECT_EQ(n, -1);
+      }
+    }
+    map.clr_bit(i);
+  }
+}
+
+TEST_VM(metaspace, leftoverbins_basics) {
+
+  LeftOverManager lom;
+  MetaWord tmp[1024];
+  metaspace::block_stats_t stats;
+
+  lom.add_block(tmp, 1024);
+  DEBUG_ONLY(lom.verify();)
+
+  lom.statistics(&stats);
+  EXPECT_EQ(stats.num_blocks, 1);
+  EXPECT_EQ(stats.word_size, (size_t)1024);
+
+  MetaWord* p = lom.get_block(1024);
+  EXPECT_EQ(p, tmp);
+  DEBUG_ONLY(lom.verify();)
+
+  lom.statistics(&stats);
+  EXPECT_EQ(stats.num_blocks, 0);
+  EXPECT_EQ(stats.word_size, (size_t)0);
+}
+
+TEST_VM(metaspace, leftoverbins_small) {
+  LeftOverBinsTest::test_small_allocations();
+}
+
+TEST_VM(metaspace, leftoverbins_medium) {
+  LeftOverBinsTest::test_medium_allocations();
+}
+
+TEST_VM(metaspace, leftoverbins_large) {
+  LeftOverBinsTest::test_large_allocations();
+}
+