1 /*
2 * Copyright (c) 2001, 2023, 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_RUNTIME_PERFMEMORY_HPP
26 #define SHARE_RUNTIME_PERFMEMORY_HPP
27
28 #include "runtime/globals.hpp"
29 #include "utilities/exceptions.hpp"
30
31 /*
32 * PerfData Version Constants
33 * - Major Version - change whenever the structure of PerfDataEntry changes
34 * - Minor Version - change whenever the data within the PerfDataEntry
35 * structure changes. for example, new unit or variability
36 * values are added or new PerfData subtypes are added.
37 */
38 #define PERFDATA_MAJOR_VERSION 2
39 #define PERFDATA_MINOR_VERSION 0
40
41 /* Byte order of the PerfData memory region. The byte order is exposed in
42 * the PerfData memory region as the data in the memory region may have
43 * been generated by a little endian JVM implementation. Tracking the byte
44 * order in the PerfData memory region allows Java applications to adapt
45 * to the native byte order for monitoring purposes. This indicator is
46 * also useful when a snapshot of the PerfData memory region is shipped
47 * to a machine with a native byte order different from that of the
48 * originating machine.
49 */
50 #define PERFDATA_BIG_ENDIAN 0
51 #define PERFDATA_LITTLE_ENDIAN 1
52
53 /*
54 * The PerfDataPrologue structure is known by the PerfDataBuffer Java class
55 * libraries that read the PerfData memory region. The size and the position
56 * of the fields must be changed along with their counterparts in the
57 * PerfDataBuffer Java class. The first four bytes of this structure
58 * should never change, or compatibility problems between the monitoring
59 * applications and HotSpot VMs will result. The reserved fields are
60 * available for future enhancements.
61 */
62 typedef struct {
63 jint magic; // magic number - 0xcafec0c0
64 jbyte byte_order; // byte order of the buffer
65 jbyte major_version; // major and minor version numbers
66 jbyte minor_version;
67 jbyte accessible; // ready to access
68 jint used; // number of PerfData memory bytes used
69 jint overflow; // number of bytes of overflow
70 jlong mod_time_stamp; // time stamp of last structural modification
71 jint entry_offset; // offset of the first PerfDataEntry
72 jint num_entries; // number of allocated PerfData entries
73 } PerfDataPrologue;
74
75 /* The PerfDataEntry structure defines the fixed portion of an entry
76 * in the PerfData memory region. The PerfDataBuffer Java libraries
77 * are aware of this structure and need to be changed when this
78 * structure changes.
79 */
80 typedef struct {
81
82 jint entry_length; // entry length in bytes
83 jint name_offset; // offset of the data item name
84 jint vector_length; // length of the vector. If 0, then scalar
85 jbyte data_type; // type of the data item -
86 // 'B','Z','J','I','S','C','D','F','V','L','['
87 jbyte flags; // flags indicating misc attributes
88 jbyte data_units; // unit of measure for the data type
89 jbyte data_variability; // variability classification of data type
90 jint data_offset; // offset of the data item
91
92 /*
93 body of PerfData memory entry is variable length
94
95 jbyte[name_length] data_name; // name of the data item
96 jbyte[pad_length] data_pad; // alignment of data item
97 j<data_type>[data_length] data_item; // array of appropriate types.
98 // data_length is > 1 only when the
99 // data_type is T_ARRAY.
100 */
101 } PerfDataEntry;
102
103 // Prefix of performance data file.
104 extern const char PERFDATA_NAME[];
105
106 // UINT_CHARS contains the number of characters holding a process id
107 // (i.e. pid). pid is defined as unsigned "int" so the maximum possible pid value
108 // would be 2^32 - 1 (4294967295) which can be represented as a 10 characters
109 // string.
110 static const size_t UINT_CHARS = 10;
111
112 /* the PerfMemory class manages creation, destruction,
113 * and allocation of the PerfData region.
114 */
115 class PerfMemory : AllStatic {
116 friend class VMStructs;
117 friend class PerfMemoryTest;
118 private:
119 static char* _start;
120 static char* _end;
121 static char* _top;
122 static size_t _capacity;
123 static PerfDataPrologue* _prologue;
124 static volatile int _initialized;
125 static volatile bool _destroyed;
126
127 static void create_memory_region(size_t sizep);
128 static void delete_memory_region();
129
130 public:
131 static char* alloc(size_t size);
132 static char* start() { return _start; }
133 static char* end() { return _end; }
134 static size_t used() { return (size_t) (_top - _start); }
135 static size_t capacity() { return _capacity; }
136 static bool is_initialized();
137 static bool is_destroyed() { return _destroyed; }
138 static bool is_usable() { return is_initialized() && !is_destroyed(); }
139 static bool contains(char* addr) {
140 return ((_start != nullptr) && (addr >= _start) && (addr < _end));
141 }
142 static void mark_updated();
143
144 // methods for attaching to and detaching from the PerfData
145 // memory segment of another JVM process on the same system.
146 static void attach(int vmid, char** addrp, size_t* size, TRAPS);
147 static void detach(char* addr, size_t bytes);
148
149 static void initialize();
150 static void destroy();
151 static void set_accessible(bool value) {
152 if (UsePerfData) {
153 _prologue->accessible = value;
154 }
155 }
156
157 // returns the complete file path of hsperfdata.
158 // the caller is expected to free the allocated memory.
159 static char* get_perfdata_file_path();
160 };
161
162 void perfMemory_init();
163 void perfMemory_exit();
164
165 #endif // SHARE_RUNTIME_PERFMEMORY_HPP