001/* MemoryPoolMXBean.java - Interface for a memory pool bean 002 Copyright (C) 2006 Free Software Foundation 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038package java.lang.management; 039 040/** 041 * <p> 042 * Provides access to information about one of the memory 043 * resources or pools used by the virtual machine. Instances 044 * of this bean are obtained by calling 045 * {@link ManagementFactory#getMemoryPoolMXBeans()}. One 046 * bean is returned for each memory pool provided. 047 * </p> 048 * <p> 049 * The memory pool bean allows the usage of the pool to be 050 * monitored. The bean can provide statistics on the current 051 * and peak usage of the pool, and on the threshold levels the 052 * pool uses. 053 * </p> 054 * <p> 055 * {@link getUsage()} returns an approximation of the current 056 * usage of the pool. Calls to this method are expected to be 057 * generally quick to perform; if the call is expensive, the 058 * documentation of the bean should specify so. For memory 059 * pool beans that represent the memory used by garbage 060 * collectors, the usage level includes both referenced and 061 * unreferenced objects. 062 * </p> 063 * <p> 064 * {@link getPeakUsage()} and {@link resetPeakUsage()} enable 065 * the retrieval of the peak usage level and setting it to the 066 * current usage level, respectively. Initially, the peak usage 067 * level is relative to the start of the virtual machine. 068 * </p> 069 * <p> 070 * Memory pools may also include optional support for usage thresholds. 071 * The usage threshold is a particular level of memory usage. When this 072 * value is crossed (the current memory usage becomes equal to or greater 073 * than this threshold level), the usage threshold count is increased. 074 * This feature is designed for monitoring the trend in memory usage. 075 * Support for a collection usage threshold is also provided, for 076 * particular garbage collectors. This is used to monitor the amount 077 * of memory left uncollected after a garbage collection cycle. There 078 * is no need to make special garbage collection runs to support this; 079 * the level following collection just needs to be monitored. 080 * </p> 081 * 082 * @author Andrew John Hughes (gnu_andrew@member.fsf.org) 083 * @since 1.5 084 */ 085public interface MemoryPoolMXBean 086{ 087 088 /** 089 * Returns memory usage statistics after a best-effort attempt 090 * has been made to remove unused objects from the pool. This 091 * method is designed for use by the pools of garbage collectors, 092 * in order to monitor the amount of memory used after collections. 093 * It will return <code>null</code> if such functionality is 094 * unsupported by the memory pool represented by this bean. 095 * 096 * @return the memory usage of the memory pool after the most 097 * recent garbage collection cycle, or <code>null</code> 098 * if this operation is not supported. 099 */ 100 MemoryUsage getCollectionUsage(); 101 102 /** 103 * Returns the collection usage threshold level in bytes. This 104 * value is initially zero. 105 * 106 * @return the collection usage threshold in bytes. 107 * @throws UnsupportedOperationException if the collection usage 108 * threshold is not supported. 109 * @see #getCollectionUsageThresholdCount() 110 * @see #isCollectionUsageThresholdExceeded() 111 * @see #isCollectionUsageThresholdSupported() 112 * @see #setCollectionUsageThreshold(long) 113 */ 114 long getCollectionUsageThreshold(); 115 116 /** 117 * Returns the number of times the usage level has matched or 118 * exceeded the collection usage threshold. 119 * 120 * @return the number of times the usage level has matched 121 * or exceeded the collection usage threshold. 122 * @throws UnsupportedOperationException if the collection usage 123 * threshold is not supported. 124 * @see #getCollectionUsageThreshold() 125 * @see #isCollectionUsageThresholdExceeded() 126 * @see #isCollectionUsageThresholdSupported() 127 * @see #setCollectionUsageThreshold(long) 128 */ 129 long getCollectionUsageThresholdCount(); 130 131 /** 132 * Returns the names of the memory managers associated with this 133 * pool. Each pool has at least one memory manager. 134 * 135 * @return an array containing the name of each memory manager 136 * responsible for this pool. 137 */ 138 String[] getMemoryManagerNames(); 139 140 /** 141 * Returns the name of the memory pool. 142 * 143 * @return the memory pool name. 144 */ 145 String getName(); 146 147 /** 148 * Returns memory usage statistics for the peak memory usage 149 * of the pool. The peak is the maximum memory usage occurring 150 * since the virtual machine was started or since the peak 151 * was reset by {@link #resetPeakUsage()}. The return value 152 * may be <code>null</code> if this pool is no longer valid. 153 * 154 * @return the memory usage of the memory pool at its peak, 155 * or <code>null</code> if this pool is no longer valid. 156 */ 157 MemoryUsage getPeakUsage(); 158 159 /** 160 * Returns the type of memory used by this pool. This can be 161 * either heap or non-heap memory. 162 * 163 * @return the type of this pool. 164 */ 165 MemoryType getType(); 166 167 /** 168 * Returns memory usage statistics for the current memory usage 169 * of the pool. The return value may be <code>null</code> if 170 * this pool is no longer valid. Obtaining these values is 171 * expected to be a relatively quick operation; if this will 172 * instead be an expensive operation to perform, the documentation 173 * of the implementating bean should specify that this is the 174 * case. The values are intended to be an estimate for monitoring 175 * purposes. 176 * 177 * @return the memory usage of the memory pool at present, 178 * or <code>null</code> if this pool is no longer valid. 179 */ 180 MemoryUsage getUsage(); 181 182 /** 183 * Returns the usage threshold level in bytes. This 184 * value is initially defined by the virtual machine. 185 * 186 * @return the usage threshold in bytes. 187 * @throws UnsupportedOperationException if the usage threshold 188 * is not supported. 189 * @see #getUsageThresholdCount() 190 * @see #isUsageThresholdExceeded() 191 * @see #isUsageThresholdSupported() 192 * @see #setUsageThreshold(long) 193 */ 194 long getUsageThreshold(); 195 196 /** 197 * Returns the number of times the usage level has matched or 198 * exceeded the usage threshold. 199 * 200 * @return the number of times the usage level has matched 201 * or exceeded the usage threshold. 202 * @throws UnsupportedOperationException if the usage threshold 203 * is not supported. 204 * @see #getUsageThreshold() 205 * @see #isUsageThresholdExceeded() 206 * @see #isUsageThresholdSupported() 207 * @see #setUsageThreshold(long) 208 */ 209 long getUsageThresholdCount(); 210 211 /** 212 * Returns true if the collection usage level is equal to 213 * or greater than the collection usage threshold. 214 * 215 * @return true if the collection usage threshold has been 216 * matched or exceeded. 217 * @throws UnsupportedOperationException if the collection usage 218 * threshold is not supported. 219 * @see #getCollectionUsageThreshold() 220 * @see #getCollectionUsageThresholdCount() 221 * @see #isCollectionUsageThresholdSupported() 222 * @see #setCollectionUsageThreshold(long) 223 */ 224 boolean isCollectionUsageThresholdExceeded(); 225 226 /** 227 * Returns true if this memory pool supports a collection usage 228 * level threshold. 229 * 230 * @return true if a collection usage level threshold is supported. 231 * @see #getCollectionUsageThreshold() 232 * @see #getCollectionUsageThresholdCount() 233 * @see #isCollectionUsageThresholdExceeded() 234 * @see #setCollectionUsageThreshold(long) 235 */ 236 boolean isCollectionUsageThresholdSupported(); 237 238 /** 239 * Returns true if the usage level is equal to 240 * or greater than the usage threshold. 241 * 242 * @return true if the usage threshold has been 243 * matched or exceeded. 244 * @throws UnsupportedOperationException if the usage threshold 245 * is not supported. 246 * @see #getUsageThreshold() 247 * @see #getUsageThresholdCount() 248 * @see #isUsageThresholdSupported() 249 * @see #setUsageThreshold(long) 250 */ 251 boolean isUsageThresholdExceeded(); 252 253 /** 254 * Returns true if this memory pool supports a usage level threshold. 255 * 256 * @return true if a usage level threshold is supported. 257 * @see #getUsageThreshold() 258 * @see #getUsageThresholdCount() 259 * @see #isUsageThresholdExceeded() 260 * @see #setUsageThreshold(long) 261 */ 262 boolean isUsageThresholdSupported(); 263 264 /** 265 * Returns true if this memory pool is still valid. A memory pool 266 * becomes invalid when it is removed by the virtual machine and 267 * no longer used. 268 * 269 * @return true if this memory pool is valid. 270 */ 271 boolean isValid(); 272 273 /** 274 * Resets the peak memory usage level to the current memory usage 275 * level. 276 * 277 * @throws SecurityException if a security manager exists and 278 * denies ManagementPermission("control"). 279 */ 280 void resetPeakUsage(); 281 282 /** 283 * Sets the collection threshold usage level to the given value. 284 * A value of zero disables the collection threshold. 285 * 286 * @param threshold the new threshold level. 287 * @throws IllegalArgumentException if the threshold hold level 288 * is negative. 289 * @throws UnsupportedOperationException if the collection usage 290 * threshold is not supported. 291 * @throws SecurityException if a security manager exists and 292 * denies ManagementPermission("control"). 293 * @see #getCollectionUsageThreshold() 294 * @see #getCollectionUsageThresholdCount() 295 * @see #isCollectionUsageThresholdExceeded() 296 * @see #isCollectionUsageThresholdSupported() 297 */ 298 void setCollectionUsageThreshold(long threshold); 299 300 /** 301 * Sets the threshold usage level to the given value. A value of 302 * zero disables the threshold. 303 * 304 * @param threshold the new threshold level. 305 * @throws IllegalArgumentException if the threshold hold level 306 * is negative. 307 * @throws UnsupportedOperationException if the usage threshold 308 * is not supported. 309 * @throws SecurityException if a security manager exists and 310 * denies ManagementPermission("control"). 311 * @see #getUsageThreshold() 312 * @see #getUsageThresholdCount() 313 * @see #isUsageThresholdExceeded() 314 * @see #isUsageThresholdSupported() 315 */ 316 void setUsageThreshold(long threshold); 317 318}