1 /* 2 * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved. 3 * Copyright (c) 2020 SAP SE. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 * 24 */ 25 26 #ifndef SHARE_MEMORY_METASPACE_COMMITLIMITER_HPP 27 #define SHARE_MEMORY_METASPACE_COMMITLIMITER_HPP 28 29 #include "memory/allocation.hpp" 30 #include "memory/metaspace/counter.hpp" 31 32 namespace metaspace { 33 34 // The CommitLimiter encapsulates a limit we may want to impose on how much 35 // memory can be committed. This is a matter of separation of concerns: 36 // 37 // In metaspace, we have two limits to committing memory: the absolute limit, 38 // MaxMetaspaceSize; and the GC threshold. In both cases an allocation should 39 // fail if it would require committing memory and hit one of these limits. 40 // 41 // However, the actual Metaspace allocator is a generic one and this 42 // GC- and classloading specific logic should be kept separate. Therefore 43 // it is hidden inside this interface. 44 // 45 // This allows us to: 46 // - more easily write tests for metaspace, by providing a different implementation 47 // of the commit limiter, thus keeping test logic separate from VM state. 48 // - (potentially) use the metaspace for things other than class metadata, 49 // where different commit rules would apply. 50 // 51 class CommitLimiter : public CHeapObj<mtMetaspace> { 52 53 // Counts total words committed for metaspace 54 SizeCounter _cnt; 55 56 // Purely for testing purposes: cap, in words. 57 const size_t _cap; 58 59 public: 60 61 // Create a commit limiter. This is only useful for testing, with a cap != 0, 62 // since normal code should use the global commit limiter. 63 // If cap != 0 (word size), the cap replaces the internal logic of limiting. 64 CommitLimiter(size_t cap = 0) : _cnt(), _cap(cap) {} 65 66 // Returns the size, in words, by which we may expand the metaspace committed area without: 67 // - _cap == 0: hitting GC threshold or the MaxMetaspaceSize 68 // - _cap > 0: hitting cap (this is just for testing purposes) 69 size_t possible_expansion_words() const; 70 71 void increase_committed(size_t word_size) { _cnt.increment_by(word_size); } 72 void decrease_committed(size_t word_size) { _cnt.decrement_by(word_size); } 73 74 size_t committed_words() const { return _cnt.get(); } 75 size_t cap() const { return _cap; } 76 77 // Returns the global metaspace commit counter 78 static CommitLimiter* globalLimiter(); 79 80 }; 81 82 } // namespace metaspace 83 84 #endif // SHARE_MEMORY_METASPACE_COMMITLIMITER_HPP