1 /*
2 * Copyright (c) 2003, 2017, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang.management;
27
28 import javax.management.openmbean.CompositeData;
29 import sun.management.MemoryUsageCompositeData;
30
31 /**
32 * A {@code MemoryUsage} object represents a snapshot of memory usage.
33 * Instances of the {@code MemoryUsage} class are usually constructed
34 * by methods that are used to obtain memory usage
35 * information about individual memory pool of the Java virtual machine or
36 * the heap or non-heap memory of the Java virtual machine as a whole.
37 *
38 * <p> A {@code MemoryUsage} object contains four values:
39 * <table class="striped">
40 * <caption style="display:none">Describes the MemoryUsage object content</caption>
41 * <thead>
42 * <tr><th scope="col">Value</th><th scope="col">Description</th></tr>
43 * </thead>
44 * <tbody style="text-align:left">
45 * <tr>
46 * <th scope="row" style="vertical-align:top"> {@code init} </th>
47 * <td style="vertical-align:top"> represents the initial amount of memory (in bytes) that
48 * the Java virtual machine requests from the operating system
49 * for memory management during startup. The Java virtual machine
50 * may request additional memory from the operating system and
51 * may also release memory to the system over time.
52 * The value of {@code init} may be undefined.
53 * </td>
54 * </tr>
55 * <tr>
56 * <th scope="row" style="vertical-align:top"> {@code used} </th>
57 * <td style="vertical-align:top"> represents the amount of memory currently used (in bytes).
58 * </td>
59 * </tr>
60 * <tr>
61 * <th scope="row" style="vertical-align:top"> {@code committed} </th>
62 * <td style="vertical-align:top"> represents the amount of memory (in bytes) that is
63 * guaranteed to be available for use by the Java virtual machine.
64 * The amount of committed memory may change over time (increase
65 * or decrease). The Java virtual machine may release memory to
66 * the system and {@code committed} could be less than {@code init}.
67 * {@code committed} will always be greater than
68 * or equal to {@code used}.
69 * </td>
70 * </tr>
71 * <tr>
72 * <th scope="row" style="vertical-align:top"> {@code max} </th>
73 * <td style="vertical-align:top"> represents the maximum amount of memory (in bytes)
74 * that can be used for memory management. Its value may be undefined.
75 * The maximum amount of memory may change over time if defined.
76 * The amount of used and committed memory will always be less than
77 * or equal to {@code max} if {@code max} is defined.
78 * A memory allocation may fail if it attempts to increase the
79 * used memory such that {@code used > committed} even
80 * if {@code used <= max} would still be true (for example,
81 * when the system is low on virtual memory).
82 * </td>
83 * </tr>
84 * </tbody>
85 * </table>
86 *
87 * Below is a picture showing an example of a memory pool:
88 *
89 * <pre>
90 * +----------------------------------------------+
91 * +//////////////// | +
92 * +//////////////// | +
93 * +----------------------------------------------+
94 *
95 * |--------|
96 * init
97 * |---------------|
98 * used
99 * |---------------------------|
100 * committed
101 * |----------------------------------------------|
102 * max
103 * </pre>
104 *
105 * <h3>MXBean Mapping</h3>
106 * {@code MemoryUsage} is mapped to a {@link CompositeData CompositeData}
107 * with attributes as specified in the {@link #from from} method.
108 *
109 * @author Mandy Chung
110 * @since 1.5
111 */
112 public class MemoryUsage {
113 private final long init;
114 private final long used;
115 private final long committed;
116 private final long max;
117
118 /**
119 * Constructs a {@code MemoryUsage} object.
120 *
121 * @param init the initial amount of memory in bytes that
122 * the Java virtual machine allocates;
123 * or {@code -1} if undefined.
124 * @param used the amount of used memory in bytes.
125 * @param committed the amount of committed memory in bytes.
126 * @param max the maximum amount of memory in bytes that
127 * can be used; or {@code -1} if undefined.
128 *
129 * @throws IllegalArgumentException if
130 * <ul>
131 * <li> the value of {@code init} or {@code max} is negative
132 * but not {@code -1}; or</li>
133 * <li> the value of {@code used} or {@code committed} is negative;
134 * or</li>
135 * <li> {@code used} is greater than the value of {@code committed};
136 * or</li>
137 * <li> {@code committed} is greater than the value of {@code max}
138 * {@code max} if defined.</li>
139 * </ul>
140 */
141 public MemoryUsage(long init,
142 long used,
143 long committed,
144 long max) {
145 if (init < -1) {
146 throw new IllegalArgumentException( "init parameter = " +
147 init + " is negative but not -1.");
148 }
149 if (max < -1) {
150 throw new IllegalArgumentException( "max parameter = " +
151 max + " is negative but not -1.");
152 }
153 if (used < 0) {
154 throw new IllegalArgumentException( "used parameter = " +
155 used + " is negative.");
156 }
157 if (committed < 0) {
158 throw new IllegalArgumentException( "committed parameter = " +
159 committed + " is negative.");
160 }
161 if (used > committed) {
162 throw new IllegalArgumentException( "used = " + used +
163 " should be <= committed = " + committed);
164 }
165 if (max >= 0 && committed > max) {
166 throw new IllegalArgumentException( "committed = " + committed +
167 " should be < max = " + max);
168 }
169
170 this.init = init;
171 this.used = used;
172 this.committed = committed;
173 this.max = max;
174 }
175
176 /**
177 * Constructs a {@code MemoryUsage} object from a
178 * {@link CompositeData CompositeData}.
179 */
180 private MemoryUsage(CompositeData cd) {
181 // validate the input composite data
182 MemoryUsageCompositeData.validateCompositeData(cd);
183
184 this.init = MemoryUsageCompositeData.getInit(cd);
185 this.used = MemoryUsageCompositeData.getUsed(cd);
186 this.committed = MemoryUsageCompositeData.getCommitted(cd);
187 this.max = MemoryUsageCompositeData.getMax(cd);
188 }
189
190 /**
191 * Returns the amount of memory in bytes that the Java virtual machine
192 * initially requests from the operating system for memory management.
193 * This method returns {@code -1} if the initial memory size is undefined.
194 *
195 * @return the initial size of memory in bytes;
196 * {@code -1} if undefined.
197 */
198 public long getInit() {
199 return init;
200 }
201
202 /**
203 * Returns the amount of used memory in bytes.
204 *
205 * @return the amount of used memory in bytes.
206 *
207 */
208 public long getUsed() {
209 return used;
210 };
211
212 /**
213 * Returns the amount of memory in bytes that is committed for
214 * the Java virtual machine to use. This amount of memory is
215 * guaranteed for the Java virtual machine to use.
216 *
217 * @return the amount of committed memory in bytes.
218 *
219 */
220 public long getCommitted() {
221 return committed;
222 };
223
224 /**
225 * Returns the maximum amount of memory in bytes that can be
226 * used for memory management. This method returns {@code -1}
227 * if the maximum memory size is undefined.
228 *
229 * <p> This amount of memory is not guaranteed to be available
230 * for memory management if it is greater than the amount of
231 * committed memory. The Java virtual machine may fail to allocate
232 * memory even if the amount of used memory does not exceed this
233 * maximum size.
234 *
235 * @return the maximum amount of memory in bytes;
236 * {@code -1} if undefined.
237 */
238 public long getMax() {
239 return max;
240 };
241
242 /**
243 * Returns a descriptive representation of this memory usage.
244 */
245 public String toString() {
246 StringBuilder buf = new StringBuilder();
247 buf.append("init = " + init + "(" + (init >> 10) + "K) ");
248 buf.append("used = " + used + "(" + (used >> 10) + "K) ");
249 buf.append("committed = " + committed + "(" +
250 (committed >> 10) + "K) " );
251 buf.append("max = " + max + "(" + (max >> 10) + "K)");
252 return buf.toString();
253 }
254
255 /**
256 * Returns a {@code MemoryUsage} object represented by the
257 * given {@code CompositeData}. The given {@code CompositeData}
258 * must contain the following attributes:
259 *
260 * <table class="striped" style="margin-left:2em;">
261 * <caption style="display:none">The attributes and the types the given CompositeData contains</caption>
262 * <thead>
263 * <tr>
264 * <th scope="col">Attribute Name</th>
265 * <th scope="col">Type</th>
266 * </tr>
267 * </thead>
268 * <tbody style="text-align:left">
269 * <tr>
270 * <th scope="row">init</th>
271 * <td>{@code java.lang.Long}</td>
272 * </tr>
273 * <tr>
274 * <th scope="row">used</th>
275 * <td>{@code java.lang.Long}</td>
276 * </tr>
277 * <tr>
278 * <th scope="row">committed</th>
279 * <td>{@code java.lang.Long}</td>
280 * </tr>
281 * <tr>
282 * <th scope="row">max</th>
283 * <td>{@code java.lang.Long}</td>
284 * </tr>
285 * </tbody>
286 * </table>
287 *
288 * @param cd {@code CompositeData} representing a {@code MemoryUsage}
289 *
290 * @throws IllegalArgumentException if {@code cd} does not
291 * represent a {@code MemoryUsage} with the attributes described
292 * above.
293 *
294 * @return a {@code MemoryUsage} object represented by {@code cd}
295 * if {@code cd} is not {@code null};
296 * {@code null} otherwise.
297 */
298 public static MemoryUsage from(CompositeData cd) {
299 if (cd == null) {
300 return null;
301 }
302
303 if (cd instanceof MemoryUsageCompositeData) {
304 return ((MemoryUsageCompositeData) cd).getMemoryUsage();
305 } else {
306 return new MemoryUsage(cd);
307 }
308
309 }
310 }
311