--- /dev/null	2020-09-04 12:37:41.765504620 +0200
+++ new/src/hotspot/share/memory/metaspace/msChunkManager.cpp	2020-09-04 13:57:44.317310515 +0200
@@ -0,0 +1,476 @@
+/*
+ * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2020 SAP SE. 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"
+
+#include "logging/log.hpp"
+#include "logging/logStream.hpp"
+#include "memory/metaspace/msArenaGrowthPolicy.hpp"
+#include "memory/metaspace/msChunkManager.hpp"
+#include "memory/metaspace/msCommon.hpp"
+#include "memory/metaspace/msContext.hpp"
+#include "memory/metaspace/msInternalStats.hpp"
+#include "memory/metaspace/msMetachunk.hpp"
+#include "memory/metaspace/msSettings.hpp"
+#include "memory/metaspace/msStatistics.hpp"
+#include "memory/metaspace/msVirtualSpaceList.hpp"
+#include "memory/metaspace/msVirtualSpaceNode.hpp"
+#include "runtime/mutexLocker.hpp"
+#include "utilities/debug.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+namespace metaspace {
+
+#define LOGFMT         "ChkMgr @" PTR_FORMAT " (%s)"
+#define LOGFMT_ARGS    p2i(this), this->_name
+
+// Return a single chunk to the freelist and adjust accounting. No merge is attempted.
+void ChunkManager::return_chunk_simple_locked(Metachunk* c) {
+
+  assert_lock_strong(MetaspaceExpand_lock);
+
+  DEBUG_ONLY(c->verify());
+
+  const chunklevel_t lvl = c->level();
+  _chunks.add(c);
+  c->reset_used_words();
+
+  // Tracing
+  log_debug(metaspace)("ChunkManager %s: returned chunk " METACHUNK_FORMAT ".",
+                       _name, METACHUNK_FORMAT_ARGS(c));
+
+}
+
+// Creates a chunk manager with a given name (which is for debug purposes only)
+// and an associated space list which will be used to request new chunks from
+// (see get_chunk())
+ChunkManager::ChunkManager(const char* name, VirtualSpaceList* space_list)
+  : _vslist(space_list),
+    _name(name),
+    _chunks()
+{
+}
+
+// Given a chunk, split it into a target chunk of a smaller size (higher target level)
+//  and at least one, possible several splinter chunks.
+// The original chunk must be outside of the freelist and its state must be free.
+// The splinter chunks are added to the freelist.
+// The resulting target chunk will be located at the same address as the original
+//  chunk, but it will of course be smaller (of a higher level).
+// The committed areas within the original chunk carry over to the resulting
+//  chunks.
+void ChunkManager::split_chunk_and_add_splinters(Metachunk* c, chunklevel_t target_level) {
+
+  assert_lock_strong(MetaspaceExpand_lock);
+
+  assert(c->is_free(), "chunk to be split must be free.");
+  assert(c->level() < target_level, "Target level must be higher than current level.");
+  assert(c->prev() == NULL && c->next() == NULL, "Chunk must be outside of any list.");
+
+  DEBUG_ONLY(chunklevel::check_valid_level(target_level);)
+  DEBUG_ONLY(c->verify();)
+
+  UL2(debug, "splitting chunk " METACHUNK_FORMAT " to " CHKLVL_FORMAT ".",
+      METACHUNK_FORMAT_ARGS(c), target_level);
+
+  DEBUG_ONLY(size_t committed_words_before = c->committed_words();)
+
+  const chunklevel_t orig_level = c->level();
+  c->vsnode()->split(target_level, c, &_chunks);
+
+  // Splitting should never fail.
+  assert(c->level() == target_level, "Sanity");
+
+  // The size of the committed portion should not change (subject to the reduced chunk size of course)
+#ifdef ASSERT
+  if (committed_words_before > c->word_size()) {
+    assert(c->is_fully_committed(), "Sanity");
+  } else {
+    assert(c->committed_words() == committed_words_before, "Sanity");
+  }
+#endif
+
+  DEBUG_ONLY(c->verify());
+
+  DEBUG_ONLY(verify_locked();)
+
+  SOMETIMES(c->vsnode()->verify_locked();)
+
+  InternalStats::inc_num_chunk_splits();
+
+}
+
+// On success, returns a chunk of level of <preferred_level>, but at most <max_level>.
+//  The first first <min_committed_words> of the chunk are guaranteed to be committed.
+// On error, will return NULL.
+//
+// This function may fail for two reasons:
+// - Either we are unable to reserve space for a new chunk (if the underlying VirtualSpaceList
+//   is non-expandable but needs expanding - aka out of compressed class space).
+// - Or, if the necessary space cannot be committed because we hit a commit limit.
+//   This may be either the GC threshold or MaxMetaspaceSize.
+Metachunk* ChunkManager::get_chunk(chunklevel_t preferred_level, chunklevel_t max_level, size_t min_committed_words) {
+
+  assert(preferred_level <= max_level, "Sanity");
+  assert(chunklevel::level_fitting_word_size(min_committed_words) >= max_level, "Sanity");
+
+  MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
+
+  DEBUG_ONLY(verify_locked();)
+
+  DEBUG_ONLY(chunklevel::check_valid_level(max_level);)
+  DEBUG_ONLY(chunklevel::check_valid_level(preferred_level);)
+  assert(max_level >= preferred_level, "invalid level.");
+
+  UL2(debug, "requested chunk: pref_level: " CHKLVL_FORMAT
+     ", max_level: " CHKLVL_FORMAT ", min committed size: " SIZE_FORMAT ".",
+     preferred_level, max_level, min_committed_words);
+
+  // First, optimistically look for a chunk which is already committed far enough to hold min_word_size.
+
+  // 1) Search best or smaller committed chunks (first attempt):
+  //    Start at the preferred chunk size and work your way down (level up).
+  //    But for now, only consider chunks larger than a certain threshold -
+  //    this is to prevent large loaders (eg boot) from unnecessarily gobbling up
+  //    all the tiny splinter chunks lambdas leave around.
+  Metachunk* c = NULL;
+  c = _chunks.search_chunk_ascending(preferred_level, MIN2((chunklevel_t)(preferred_level + 2), max_level), min_committed_words);
+
+  // 2) Search larger committed chunks:
+  //    If that did not yield anything, look at larger chunks, which may be committed. We would have to split
+  //    them first, of course.
+  if (c == NULL) {
+    c = _chunks.search_chunk_descending(preferred_level, min_committed_words);
+  }
+
+  // 3) Search best or smaller committed chunks (second attempt):
+  //    Repeat (1) but now consider even the tiniest chunks as long as they are large enough to hold the
+  //    committed min size.
+  if (c == NULL) {
+    c = _chunks.search_chunk_ascending(preferred_level, max_level, min_committed_words);
+  }
+
+  // if we did not get anything yet, there are no free chunks commmitted enough. Repeat search but look for uncommitted chunks too:
+
+  // 4) Search best or smaller chunks, can be uncommitted:
+  if (c == NULL) {
+    c = _chunks.search_chunk_ascending(preferred_level, max_level, 0);
+  }
+
+  // 5) Search a larger uncommitted chunk:
+  if (c == NULL) {
+    c = _chunks.search_chunk_descending(preferred_level, 0);
+  }
+
+  if (c != NULL) {
+    UL(trace, "taken from freelist.");
+  }
+
+  // Failing all that, allocate a new root chunk from the connected virtual space.
+  // This may fail if the underlying vslist cannot be expanded (e.g. compressed class space)
+  if (c == NULL) {
+    c = _vslist->allocate_root_chunk();
+    if (c == NULL) {
+      UL(info, "failed to get new root chunk.");
+    } else {
+      assert(c->level() == chunklevel::ROOT_CHUNK_LEVEL, "root chunk expected");
+      UL(debug, "allocated new root chunk.");
+    }
+  }
+
+  if (c == NULL) {
+    // If we end up here, we found no match in the freelists and were unable to get a new
+    // root chunk (so we used up all address space, e.g. out of CompressedClassSpace).
+    UL2(info, "failed to get chunk (preferred level: " CHKLVL_FORMAT
+       ", max level " CHKLVL_FORMAT ".", preferred_level, max_level);
+    c = NULL;
+  }
+
+  if (c != NULL) {
+
+    // Now we have a chunk.
+    //  It may be larger than what the caller wanted, so we may want to split it. This should
+    //  always work.
+    if (c->level() < preferred_level) {
+      split_chunk_and_add_splinters(c, preferred_level);
+      assert(c->level() == preferred_level, "split failed?");
+    }
+
+    // Attempt to commit the chunk (depending on settings, we either fully commit it or just
+    //  commit enough to get the caller going). That may fail if we hit a commit limit. In
+    //  that case put the chunk back to the freelist (re-merging it with its neighbors if we
+    //  did split it) and return NULL.
+    const size_t to_commit = Settings::new_chunks_are_fully_committed() ? c->word_size() : min_committed_words;
+    if (c->committed_words() < to_commit) {
+      if (c->ensure_committed_locked(to_commit) == false) {
+        UL2(info, "failed to commit " SIZE_FORMAT " words on chunk " METACHUNK_FORMAT ".",
+            to_commit,  METACHUNK_FORMAT_ARGS(c));
+        c->set_in_use(); // gets asserted in return_chunk().
+        return_chunk_locked(c);
+        c = NULL;
+      }
+    }
+
+    if (c != NULL) {
+
+      // Still here? We have now a good chunk, all is well.
+      assert(c->committed_words() >= min_committed_words, "Sanity");
+
+      // Any chunk returned from ChunkManager shall be marked as in use.
+      c->set_in_use();
+
+      UL2(debug, "handing out chunk " METACHUNK_FORMAT ".", METACHUNK_FORMAT_ARGS(c));
+
+      InternalStats::inc_num_chunks_taken_from_freelist();
+
+      SOMETIMES(c->vsnode()->verify_locked();)
+
+    }
+
+  }
+
+  DEBUG_ONLY(verify_locked();)
+
+  return c;
+
+}
+
+// Return a single chunk to the ChunkManager and adjust accounting. May merge chunk
+//  with neighbors.
+// As a side effect this removes the chunk from whatever list it has been in previously.
+// Happens after a Classloader was unloaded and releases its metaspace chunks.
+// !! Note: this may invalidate the chunk. Do not access the chunk after
+//    this function returns !!
+void ChunkManager::return_chunk(Metachunk* c) {
+  MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
+  return_chunk_locked(c);
+}
+
+// See return_chunk().
+void ChunkManager::return_chunk_locked(Metachunk* c) {
+
+  assert_lock_strong(MetaspaceExpand_lock);
+
+  UL2(debug, ": returning chunk " METACHUNK_FORMAT ".", METACHUNK_FORMAT_ARGS(c));
+
+  DEBUG_ONLY(c->verify();)
+
+  assert(contains_chunk(c) == false, "A chunk to be added to the freelist must not be in the freelist already.");
+
+  assert(c->is_in_use(), "Unexpected chunk state");
+  assert(!c->in_list(), "Remove from list first");
+  c->set_free();
+  c->reset_used_words();
+
+  const chunklevel_t orig_lvl = c->level();
+
+  Metachunk* merged = NULL;
+  if (!c->is_root_chunk()) {
+    // Only attempt merging if we are not of the lowest level already.
+    merged = c->vsnode()->merge(c, &_chunks);
+  }
+
+  if (merged != NULL) {
+
+    InternalStats::inc_num_chunk_merges();
+
+    DEBUG_ONLY(merged->verify());
+
+    // We did merge our chunk into a different chunk.
+
+    // We did merge chunks and now have a bigger chunk.
+    assert(merged->level() < orig_lvl, "Sanity");
+
+    UL2(debug, "merged into chunk " METACHUNK_FORMAT ".", METACHUNK_FORMAT_ARGS(merged));
+
+    c = merged;
+
+  }
+
+  if (Settings::uncommit_free_chunks() &&
+      c->word_size() >= Settings::commit_granule_words())
+  {
+    UL2(debug, "uncommitting free chunk " METACHUNK_FORMAT ".", METACHUNK_FORMAT_ARGS(c));
+    c->uncommit_locked();
+  }
+
+  return_chunk_simple_locked(c);
+
+  DEBUG_ONLY(verify_locked();)
+  SOMETIMES(c->vsnode()->verify_locked();)
+
+  InternalStats::inc_num_chunks_returned_to_freelist();
+
+}
+
+// Given a chunk c, whose state must be "in-use" and must not be a root chunk, attempt to
+// enlarge it in place by claiming its trailing buddy.
+//
+// This will only work if c is the leader of the buddy pair and the trailing buddy is free.
+//
+// If successful, the follower chunk will be removed from the freelists, the leader chunk c will
+// double in size (level decreased by one).
+//
+// On success, true is returned, false otherwise.
+bool ChunkManager::attempt_enlarge_chunk(Metachunk* c) {
+  MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
+  return c->vsnode()->attempt_enlarge_chunk(c, &_chunks);
+}
+
+static void print_word_size_delta(outputStream* st, size_t word_size_1, size_t word_size_2) {
+  if (word_size_1 == word_size_2) {
+    print_scaled_words(st, word_size_1);
+    st->print (" (no change)");
+  } else {
+    print_scaled_words(st, word_size_1);
+    st->print("->");
+    print_scaled_words(st, word_size_2);
+    st->print(" (");
+    if (word_size_2 <= word_size_1) {
+      st->print("-");
+      print_scaled_words(st, word_size_1 - word_size_2);
+    } else {
+      st->print("+");
+      print_scaled_words(st, word_size_2 - word_size_1);
+    }
+    st->print(")");
+  }
+}
+
+void ChunkManager::purge() {
+
+  MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
+
+  UL(info, ": reclaiming memory...");
+
+  const size_t reserved_before = _vslist->reserved_words();
+  const size_t committed_before = _vslist->committed_words();
+  int num_nodes_purged = 0;
+
+  // 1) purge virtual space list
+  num_nodes_purged = _vslist->purge(&_chunks);
+  InternalStats::inc_num_purges();
+
+  // 2) uncommit free chunks
+  if (Settings::uncommit_free_chunks()) {
+    const chunklevel_t max_level =
+        chunklevel::level_fitting_word_size(Settings::commit_granule_words());
+    for (chunklevel_t l = chunklevel::LOWEST_CHUNK_LEVEL;
+         l <= max_level;
+         l++)
+    {
+      // Since we uncommit all chunks at this level, we do not break the "committed chunks are
+      //  at the front of the list" condition.
+      for (Metachunk* c = _chunks.first_at_level(l); c != NULL; c = c->next()) {
+        c->uncommit_locked();
+      }
+    }
+  }
+
+  const size_t reserved_after = _vslist->reserved_words();
+  const size_t committed_after = _vslist->committed_words();
+
+  // Print a nice report.
+  if (reserved_after == reserved_before && committed_after == committed_before) {
+    UL(info, "nothing reclaimed.");
+  } else {
+    LogTarget(Info, metaspace) lt;
+    if (lt.is_enabled()) {
+      LogStream ls(lt);
+      ls.print_cr(LOGFMT ": finished reclaiming memory: ", LOGFMT_ARGS);
+
+      ls.print("reserved: ");
+      print_word_size_delta(&ls, reserved_before, reserved_after);
+      ls.cr();
+
+      ls.print("committed: ");
+      print_word_size_delta(&ls, committed_before, committed_after);
+      ls.cr();
+
+      ls.print_cr("full nodes purged: %d", num_nodes_purged);
+    }
+  }
+
+  DEBUG_ONLY(_vslist->verify_locked());
+  DEBUG_ONLY(verify_locked());
+
+}
+
+// Convenience methods to return the global class-space chunkmanager
+//  and non-class chunkmanager, respectively.
+ChunkManager* ChunkManager::chunkmanager_class() {
+  return MetaspaceContext::context_class() == NULL ? NULL : MetaspaceContext::context_class()->cm();
+}
+
+ChunkManager* ChunkManager::chunkmanager_nonclass() {
+  return MetaspaceContext::context_nonclass() == NULL ? NULL : MetaspaceContext::context_nonclass()->cm();
+}
+
+// Update statistics.
+void ChunkManager::add_to_statistics(ChunkManagerStats* out) const {
+
+  MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
+
+  for (chunklevel_t l = chunklevel::ROOT_CHUNK_LEVEL; l <= chunklevel::HIGHEST_CHUNK_LEVEL; l++) {
+    out->_num_chunks[l] += _chunks.num_chunks_at_level(l);
+    out->_committed_word_size[l] += _chunks.committed_word_size_at_level(l);
+  }
+
+  DEBUG_ONLY(out->verify();)
+
+}
+
+#ifdef ASSERT
+
+void ChunkManager::verify() const {
+  MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
+  verify_locked();
+}
+
+void ChunkManager::verify_locked() const {
+  assert_lock_strong(MetaspaceExpand_lock);
+  assert(_vslist != NULL, "No vslist");
+  _chunks.verify();
+}
+
+bool ChunkManager::contains_chunk(Metachunk* c) const {
+  return _chunks.contains(c);
+}
+
+#endif // ASSERT
+
+void ChunkManager::print_on(outputStream* st) const {
+  MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
+  print_on_locked(st);
+}
+
+void ChunkManager::print_on_locked(outputStream* st) const {
+  assert_lock_strong(MetaspaceExpand_lock);
+  st->print_cr("cm %s: %d chunks, total word size: " SIZE_FORMAT ", committed word size: " SIZE_FORMAT, _name,
+               total_num_chunks(), total_word_size(), _chunks.committed_word_size());
+  _chunks.print_on(st);
+}
+
+} // namespace metaspace