Source for java.lang.management.MemoryUsage

   1: /* MemoryUsage.java - Information on the usage of a memory pool.
   2:    Copyright (C) 2006 Free Software Foundation
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package java.lang.management;
  39: 
  40: import javax.management.openmbean.CompositeData;
  41: import javax.management.openmbean.CompositeType;
  42: import javax.management.openmbean.SimpleType;
  43: /**
  44:  * <p>
  45:  * Retains information on the usage of a particular memory
  46:  * pool, or heap/non-heap memory as a whole.  Memory usage
  47:  * is represented by four values (all in bytes):
  48:  * </p>
  49:  * <ul>
  50:  * <li><strong>Initial Level</strong>: This is the initial
  51:  * amount of memory allocated for the pool by the operating
  52:  * system.  This value may be undefined.</li>
  53:  * <li><strong>Used Level</strong>: This is the amount of
  54:  * memory currently in use.</li>
  55:  * <li><strong>Committed Level</strong>: This is the current
  56:  * amount of memory allocated for the pool by the operating
  57:  * system.  This value will always be equal to or greater than
  58:  * the current amount of memory in use.  It may drop below
  59:  * the initial amount, if the virtual machine judges this to
  60:  * be practical.</li>
  61:  * <li><strong>Maximum Level</strong>: This is the maximum
  62:  * amount of memory that may be allocated for the pool by
  63:  * the operating system.  Like the initial amount, it may
  64:  * be undefined.  If it is defined, it will be greater than
  65:  * or equal to the used and committed amounts and may change
  66:  * over time.  It is not guaranteed that the maximum amount
  67:  * of memory may actually be allocated to the pool.  For
  68:  * example, a request for an amount of memory greater than
  69:  * the current committed level, but less than the maximum,
  70:  * may still fail due to resources at the operating system
  71:  * level not being sufficient to fulfill the demand.</li>
  72:  * </ul>
  73:  *
  74:  * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
  75:  * @since 1.5
  76:  * @see MemoryMXBean
  77:  * @see MemoryPoolMXBean
  78:  */
  79: public class MemoryUsage
  80: {
  81: 
  82:   /**
  83:    * The initial amount of memory allocated.
  84:    */
  85:   private long init;
  86: 
  87:   /**
  88:    * The amount of memory used.
  89:    */
  90:   private long used;
  91: 
  92:   /**
  93:    * The amount of memory committed for use.
  94:    */
  95:   private long committed;
  96: 
  97:   /**
  98:    * The maximum amount of memory available.
  99:    */
 100:   private long maximum;
 101: 
 102:   /**
 103:    * Constructs a new {@link MemoryUsage} object with
 104:    * the specified allocation levels.
 105:    *
 106:    * @param init the initial amount of memory allocated,
 107:    *             or -1 if this value is undefined.  Must
 108:    *             be >= -1.
 109:    * @param used the amount of memory used.  Must be >= 0,
 110:    *             and <= committed.
 111:    * @param committed the amount of memory committed for use
 112:    *                  at present.  Must be >= 0 and <=
 113:    *                  maximum (if defined).
 114:    * @param maximum the maximum amount of memory that may be
 115:    *                used, or -1 if this value is undefined.
 116:    *                Must be >= -1.
 117:    * @throws IllegalArgumentException if the values break any
 118:    *                                  of the limits specified
 119:    *                                  above.
 120:    */
 121:   public MemoryUsage(long init, long used, long committed,
 122:                      long maximum)
 123:   {
 124:     if (init < -1)
 125:       throw new IllegalArgumentException("Initial value of "
 126:                                          + init + " is too small.");
 127:     if (used < 0)
 128:       throw new IllegalArgumentException("Used value of "
 129:                                          + used + " is too small.");
 130:     if (committed < 0)
 131:       throw new IllegalArgumentException("Committed value of "
 132:                                          + committed + " is too small.");
 133:     if (committed < used)
 134:       throw new IllegalArgumentException("Committed value of "
 135:                                          + committed + " is below "
 136:                                          + used + ", the amount used.");
 137:     if (maximum < -1)
 138:       throw new IllegalArgumentException("Maximum value of "
 139:                                          + maximum + " is too small.");
 140:     if (maximum != -1 && maximum < committed)
 141:       throw new IllegalArgumentException("Maximum value of "
 142:                                          + maximum + " is below "
 143:                                          + committed + ", the amount "
 144:                                          + "committed.");
 145:     this.init = init;
 146:     this.used = used;
 147:     this.committed = committed;
 148:     this.maximum = maximum;
 149:   }
 150: 
 151:   /**
 152:    * <p>
 153:    * Returns a {@link MemoryUsage} instance using the values
 154:    * given in the supplied
 155:    * {@link javax.management.openmbean.CompositeData} object.
 156:    * The composite data instance should contain the following
 157:    * attributes:
 158:    * </p>
 159:    * <ul>
 160:    * <li>init</li>
 161:    * <li>used</li>
 162:    * <li>committed</li>
 163:    * <li>max</li>
 164:    * </ul>
 165:    * <p>
 166:    * All should have the type, <code>java.lang.Long</code>.
 167:    * </p>
 168:    *
 169:    * @param data the composite data structure to take values from.
 170:    * @return a new instance containing the values from the
 171:    *         composite data structure, or <code>null</code>
 172:    *         if the data structure was also <code>null</code>.
 173:    * @throws IllegalArgumentException if the composite data structure
 174:    *                                  does not match the structure
 175:    *                                  outlined above, or the values
 176:    *                                  are invalid.
 177:    */
 178:   public static MemoryUsage from(CompositeData data)
 179:   {
 180:     if (data == null)
 181:       return null;
 182:     CompositeType type = data.getCompositeType();
 183:     ThreadInfo.checkAttribute(type, "Init", SimpleType.LONG);
 184:     ThreadInfo.checkAttribute(type, "Used", SimpleType.LONG);
 185:     ThreadInfo.checkAttribute(type, "Committed", SimpleType.LONG);
 186:     ThreadInfo.checkAttribute(type, "Max", SimpleType.LONG);
 187:     return new MemoryUsage(((Long) data.get("Init")).longValue(),
 188:                            ((Long) data.get("Used")).longValue(),
 189:                            ((Long) data.get("Committed")).longValue(),
 190:                            ((Long) data.get("Max")).longValue());
 191:   }
 192: 
 193:   /**
 194:    * Returns the amount of memory committed for use by this
 195:    * memory pool (in bytes).  This amount is guaranteed to
 196:    * be available, unlike the maximum.
 197:    *
 198:    * @return the committed amount of memory.
 199:    */
 200:   public long getCommitted()
 201:   {
 202:     return committed;
 203:   }
 204: 
 205:   /**
 206:    * Returns the initial amount of memory allocated to the
 207:    * pool (in bytes).  This method may return -1, if the
 208:    * value is undefined.
 209:    *
 210:    * @return the initial amount of memory allocated, or -1
 211:    *         if this value is undefined.
 212:    */
 213:   public long getInit()
 214:   {
 215:     return init;
 216:   }
 217: 
 218:   /**
 219:    * Returns the maximum amount of memory available for this
 220:    * pool (in bytes).  This amount is not guaranteed to
 221:    * actually be usable.  This method may return -1, if the
 222:    * value is undefined.
 223:    *
 224:    * @return the maximum amount of memory available, or -1
 225:    *         if this value is undefined.
 226:    */
 227:   public long getMax()
 228:   {
 229:     return maximum;
 230:   }
 231: 
 232:   /**
 233:    * Returns the amount of memory used (in bytes).
 234:    *
 235:    * @return the amount of used memory.
 236:    */
 237:   public long getUsed()
 238:   {
 239:     return used;
 240:   }
 241: 
 242:   /**
 243:    * Returns a {@link java.lang.String} representation of
 244:    * this {@link MemoryUsage} object.  This takes the form
 245:    * <code>java.lang.management.MemoryUsage[init=i, used=u,
 246:    * committed=c, maximum=m]</code>, where <code>i</code>
 247:    * is the initial level, <code>u</code> is the used level,
 248:    * <code>c</code> is the committed level and <code>m</code>
 249:    * is the maximum level.
 250:    *
 251:    * @return the string specified above.
 252:    */
 253:   public String toString()
 254:   {
 255:     int megabyte = 1024 * 1024;
 256:     return getClass().getName() +
 257:       "[init=" + init + " bytes (~" + (init / megabyte) +
 258:       "MB), used=" + used + " bytes (~" + (used / megabyte) +
 259:       "MB), committed=" + committed + " bytes (~" + (committed / megabyte) +
 260:       "MB), maximum=" + maximum + " bytes (~" + (maximum / megabyte) +
 261:       "MB)]";
 262:   }
 263: 
 264: }