--- /dev/null	2020-09-04 12:37:41.765504620 +0200
+++ new/src/hotspot/share/memory/metaspace/msCommitLimiter.hpp	2020-09-04 13:57:48.117335984 +0200
@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 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.
+ *
+ */
+
+#ifndef SHARE_MEMORY_METASPACE_MSCOMMITLIMITER_HPP
+#define SHARE_MEMORY_METASPACE_MSCOMMITLIMITER_HPP
+
+#include "memory/allocation.hpp"
+#include "memory/metaspace/msCounter.hpp"
+
+namespace metaspace {
+
+// The CommitLimiter encapsulates a limit we may want to impose on how much
+//  memory can be committed. This is a matter of separation of concerns:
+//
+// In metaspace, we have two limits to committing memory: the absolute limit,
+//  MaxMetaspaceSize; and the GC threshold. In both cases an allocation should
+//  fail if it would require committing memory and hit one of these limits.
+//
+// However, the actual Metaspace allocator is a generic one and this
+//  GC- and classloading specific logic should be kept separate. Therefore
+//  it is hidden inside this interface.
+//
+// This allows us to:
+//  - more easily write tests for metaspace, by providing a different implementation
+//    of the commit limiter, thus keeping test logic separate from VM state.
+//  - (potentially) use the metaspace for things other than class metadata,
+//    where different commit rules would apply.
+//
+class CommitLimiter : public CHeapObj<mtMetaspace> {
+
+  // Counts total words committed for metaspace
+  SizeCounter _cnt;
+
+  // Purely for testing purposes: cap, in words.
+  const size_t _cap;
+
+public:
+
+  // Create a commit limiter. This is only useful for testing, with a cap != 0,
+  // since normal code should use the global commit limiter.
+  // If cap != 0 (word size), the cap replaces the internal logic of limiting.
+  CommitLimiter(size_t cap = 0) : _cnt(), _cap(cap) {}
+
+  // Returns the size, in words, by which we may expand the metaspace committed area without:
+  // - _cap == 0: hitting GC threshold or the MaxMetaspaceSize
+  // - _cap > 0: hitting cap (this is just for testing purposes)
+  size_t possible_expansion_words() const;
+
+  void increase_committed(size_t word_size)   { _cnt.increment_by(word_size); }
+  void decrease_committed(size_t word_size)   { _cnt.decrement_by(word_size); }
+
+  size_t committed_words() const              { return _cnt.get(); }
+  size_t cap() const                          { return _cap; }
+
+  // Returns the global metaspace commit counter
+  static CommitLimiter* globalLimiter();
+
+};
+
+} // namespace metaspace
+
+#endif // SHARE_MEMORY_METASPACE_MSCOMMITLIMITER_HPP