perfMemory.hpp revision 7192:795fc0cef7c9 
1/*
2 * Copyright (c) 2001, 2010, 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_RUNTIME_PERFMEMORY_HPP
26#define SHARE_VM_RUNTIME_PERFMEMORY_HPP
27
28#include "utilities/exceptions.hpp"
29
30/*
31 * PerfData Version Constants
32 *   - Major Version - change whenever the structure of PerfDataEntry changes
33 *   - Minor Version - change whenever the data within the PerfDataEntry
34 *                     structure changes. for example, new unit or variability
35 *                     values are added or new PerfData subtypes are added.
36 */
37#define PERFDATA_MAJOR_VERSION 2
38#define PERFDATA_MINOR_VERSION 0
39
40/* Byte order of the PerfData memory region. The byte order is exposed in
41 * the PerfData memory region as the data in the memory region may have
42 * been generated by a little endian JVM implementation. Tracking the byte
43 * order in the PerfData memory region allows Java applications to adapt
44 * to the native byte order for monitoring purposes. This indicator is
45 * also useful when a snapshot of the PerfData memory region is shipped
46 * to a machine with a native byte order different from that of the
47 * originating machine.
48 */
49#define PERFDATA_BIG_ENDIAN     0
50#define PERFDATA_LITTLE_ENDIAN  1
51
52/*
53 * The PerfDataPrologue structure is known by the PerfDataBuffer Java class
54 * libraries that read the PerfData memory region. The size and the position
55 * of the fields must be changed along with their counterparts in the
56 * PerfDataBuffer Java class. The first four bytes of this structure
57 * should never change, or compatibility problems between the monitoring
58 * applications and HotSpot VMs will result. The reserved fields are
59 * available for future enhancements.
60 */
61typedef struct {
62  jint   magic;              // magic number - 0xcafec0c0
63  jbyte  byte_order;         // byte order of the buffer
64  jbyte  major_version;      // major and minor version numbers
65  jbyte  minor_version;
66  jbyte  accessible;         // ready to access
67  jint   used;               // number of PerfData memory bytes used
68  jint   overflow;           // number of bytes of overflow
69  jlong  mod_time_stamp;     // time stamp of last structural modification
70  jint   entry_offset;       // offset of the first PerfDataEntry
71  jint   num_entries;        // number of allocated PerfData entries
72} PerfDataPrologue;
73
74/* The PerfDataEntry structure defines the fixed portion of an entry
75 * in the PerfData memory region. The PerfDataBuffer Java libraries
76 * are aware of this structure and need to be changed when this
77 * structure changes.
78 */
79typedef struct {
80
81  jint entry_length;      // entry length in bytes
82  jint name_offset;       // offset of the data item name
83  jint vector_length;     // length of the vector. If 0, then scalar
84  jbyte data_type;        // type of the data item -
85                          // 'B','Z','J','I','S','C','D','F','V','L','['
86  jbyte flags;            // flags indicating misc attributes
87  jbyte data_units;       // unit of measure for the data type
88  jbyte data_variability; // variability classification of data type
89  jint  data_offset;      // offset of the data item
90
91/*
92  body of PerfData memory entry is variable length
93
94  jbyte[name_length] data_name;        // name of the data item
95  jbyte[pad_length] data_pad;          // alignment of data item
96  j<data_type>[data_length] data_item; // array of appropriate types.
97                                       // data_length is > 1 only when the
98                                       // data_type is T_ARRAY.
99*/
100} PerfDataEntry;
101
102// Prefix of performance data file.
103extern const char PERFDATA_NAME[];
104
105// UINT_CHARS contains the number of characters holding a process id
106// (i.e. pid). pid is defined as unsigned "int" so the maximum possible pid value
107// would be 2^32 - 1 (4294967295) which can be represented as a 10 characters
108// string.
109static const size_t UINT_CHARS = 10;
110
111/* the PerfMemory class manages creation, destruction,
112 * and allocation of the PerfData region.
113 */
114class PerfMemory : AllStatic {
115    friend class VMStructs;
116  private:
117    static char*  _start;
118    static char*  _end;
119    static char*  _top;
120    static size_t _capacity;
121    static PerfDataPrologue*  _prologue;
122    static jint   _initialized;
123
124    static void create_memory_region(size_t sizep);
125    static void delete_memory_region();
126
127  public:
128    enum PerfMemoryMode {
129      PERF_MODE_RO = 0,
130      PERF_MODE_RW = 1
131    };
132
133    static char* alloc(size_t size);
134    static char* start() { return _start; }
135    static char* end() { return _end; }
136    static size_t used() { return (size_t) (_top - _start); }
137    static size_t capacity() { return _capacity; }
138    static bool is_initialized() { return _initialized != 0; }
139    static bool contains(char* addr) {
140      return ((_start != NULL) && (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(const char* user, int vmid, PerfMemoryMode mode,
147                       char** addrp, size_t* size, TRAPS);
148    static void detach(char* addr, size_t bytes, TRAPS);
149
150    static void initialize();
151    static void destroy();
152    static void set_accessible(bool value) {
153      if (UsePerfData) {
154        _prologue->accessible = value;
155      }
156    }
157
158    // returns the complete file path of hsperfdata.
159    // the caller is expected to free the allocated memory.
160    static char* get_perfdata_file_path();
161};
162
163void perfMemory_init();
164void perfMemory_exit();
165
166#endif // SHARE_VM_RUNTIME_PERFMEMORY_HPP
167