1 /* 2 * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_JFR_METADATA_JFRCONSTANTSERIALIZER_HPP 26 #define SHARE_VM_JFR_METADATA_JFRCONSTANTSERIALIZER_HPP 27 28 #include "memory/allocation.hpp" 29 #include "jfr/recorder/checkpoint/jfrCheckpointWriter.hpp" 30 #include "tracefiles/traceTypes.hpp" 31 32 /* 33 * A JfrConstant (type) is a relation defined by enumerating a set of <key, value> ordered pairs: 34 * 35 * { <1, "my_first_constant">, <2, "my_second_constant">, ... } 36 * 37 * Write the key into event fields and the framework will maintain the mapping (if you register as below). 38 * 39 * In order to support mapping of constants, we use an interface called JfrConstantSerializer. 40 * Inherit JfrConstantSerializer, create a CHeapObj instance and use JfrConstantSerializer::register_serializer(...) to register. 41 * Once registered, the ownership of the serializer instance is transferred to Jfr. 42 * 43 * How to register: 44 * 45 * bool register_serializer(JfrConstantTypeId id, bool require_safepoint, bool permit_cache, JfrConstantSerializer* serializer) 46 * 47 * The constant types are machine generated into an enum located in tracefiles/traceTypes.hpp (included). 48 * 49 * enum JfrConstantTypeId { 50 * ... 51 * CONSTANT_TYPE_THREADGROUP, 52 * CONSTANT_TYPE_CLASSLOADER, 53 * CONSTANT_TYPE_METHOD, 54 * CONSTANT_TYPE_SYMBOL, 55 * CONSTANT_TYPE_THREADSTATE, 56 * CONSTANT_TYPE_INFLATECAUSE, 57 * ... 58 * 59 * id this is the id of the constant type your are defining (see the enum above). 60 * require_safepoint indicate if your constants need to be evaluated and written under a safepoint. 61 * permit_cache indicate if your constants are stable to be cached. 62 * (implies the callback is invoked only once and the contents will be cached. Set this to true for static information). 63 * serializer the serializer instance you define. 64 * 65 * See below for guidance about how to implement write_constants(). 66 * 67 */ 68 class JfrConstantSerializer : public CHeapObj<mtTracing> { 69 public: 70 virtual void write_constants(JfrCheckpointWriter& writer) = 0; 71 virtual ~JfrConstantSerializer() {} 72 static bool register_serializer(JfrConstantTypeId id, bool require_safepoint, bool permit_cache, JfrConstantSerializer* serializer); 73 }; 74 75 /* 76 * Invoke writer.write_number_of_constants(num) to define the total number of constant mappings. 77 * 78 * You then write the individual constants as ordered pairs, <key, value> ... 79 * 80 * Here is an example: 81 * 82 * void MyConstant::write_constants(JfrCheckpointWriter& writer) { 83 * const int nof_causes = ObjectSynchronizer::inflate_cause_nof; 84 * writer.write_number_of_constants(nof_causes); // write number of constant (mappings) to follow 85 * for (int i = 0; i < nof_causes; i++) { 86 * writer.write_key(i); // write key 87 * writer.write(ObjectSynchronizer::inflate_cause_name((ObjectSynchronizer::InflateCause)i)); // write value 88 * } 89 * } 90 * 91 * Please see jfr/recorder/checkpoint/constant/jfrConstant.cpp for reference. 92 */ 93 94 #endif // SHARE_VM_JFR_METADATA_JFRCONSTANTSERIALIZER_HPP