libjava/classpath/vm/reference/gnu/java/lang/management/VMThreadMXBeanImpl.java

   1 /* VMThreadMXBeanImpl.java - VM impl. of a thread bean
   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 gnu.java.lang.management;
  39
  40 import java.lang.management.ThreadInfo;
  41
  42 /**
  43  * Provides access to information about the threads
  44  * of the virtual machine.  An instance of this bean is
  45  * obtained by calling
  46  * {@link ManagementFactory#getThreadMXBean()}.
  47  * See {@link java.lang.management.ThreadMXBean} for
  48  * full documentation.
  49  *
  50  * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
  51  * @since 1.5
  52  */
  53 final class VMThreadMXBeanImpl
  54 {
  55
  56   /**
  57    * Cache of how many threads were found.
  58    */
  59   private static int filled;
  60
  61   /**
  62    * Returns the ids of cycles of deadlocked threads, occurring
  63    * due to monitor ownership.
  64    *
  65    * @return the ids of the deadlocked threads.
  66    */
  67   static native long[] findMonitorDeadlockedThreads();
  68
  69   /* This is the same as in Thread.getAllStackTraces() */
  70   static Thread[] getAllThreads()
  71   {
  72     ThreadGroup group = Thread.currentThread().getThreadGroup();
  73     while (group.getParent() != null)
  74       group = group.getParent();
  75     int arraySize = group.activeCount();
  76     Thread[] threadList = new Thread[arraySize];
  77     filled = group.enumerate(threadList);
  78     while (filled == arraySize)
  79       {
  80         arraySize *= 2;
  81         threadList = new Thread[arraySize];
  82         filled = group.enumerate(threadList);
  83       }
  84     return threadList;
  85   }
  86
  87   /**
  88    * Returns the id of all live threads at the time of execution.
  89    *
  90    * @return the live thread ids.
  91    */
  92   static long[] getAllThreadIds()
  93   {
  94     Thread[] threadList = getAllThreads();
  95     long[] ids = new long[filled];
  96     for (int a = 0; a < filled; ++a)
  97       ids[a] = threadList[a].getId();
  98     return ids;
  99   }
 100
 101   /**
 102    * Returns the number of nanoseconds of CPU time
 103    * the current thread has used in total.   This is
 104    * only called if this feature is enabled and
 105    * supported.
 106    *
 107    * @return the nanoseconds of CPU time used by
 108    *         the current thread.
 109    */
 110   static native long getCurrentThreadCpuTime();
 111
 112   /**
 113    * Returns the number of nanoseconds of user time
 114    * the current thread has used in total.   This is
 115    * only called if this feature is enabled and
 116    * supported.
 117    *
 118    * @return the nanoseconds of user time used by
 119    *         the current thread.
 120    */
 121   static native long getCurrentThreadUserTime();
 122
 123   /**
 124    * Returns the number of live daemon threads.
 125    *
 126    * @return the number of live daemon threads.
 127    */
 128   static int getDaemonThreadCount()
 129   {
 130     Thread[] threadList = getAllThreads();
 131     int daemonCount = 0;
 132     for (int a = 0; a < filled; ++a)
 133       {
 134         if (threadList[a].isDaemon())
 135           ++daemonCount;
 136       }
 137     return daemonCount;
 138   }
 139
 140   /**
 141    * Returns the current peak number of live threads.
 142    *
 143    * @return the peak number of live threads.
 144    */
 145   static native int getPeakThreadCount();
 146
 147   /**
 148    * Returns the number of live threads.
 149    *
 150    * @return the number of live threads.
 151    */
 152   static int getThreadCount()
 153   {
 154     getAllThreads();
 155     return filled;
 156   }
 157
 158   /**
 159    * Returns the number of nanoseconds of CPU time
 160    * the specified thread has used in total.   This is
 161    * only called if this feature is enabled and
 162    * supported.
 163    *
 164    * @param id the thread to obtain statistics on.
 165    * @return the nanoseconds of CPU time used by
 166    *         the thread.
 167    */
 168   static native long getThreadCpuTime(long id);
 169
 170   /**
 171    * Returns the {@link java.lang.management.ThreadInfo}
 172    * which corresponds to the specified id.
 173    *
 174    * @param id the id of the thread.
 175    * @param maxDepth the depth of the stack trace.
 176    * @return the corresponding <code>ThreadInfo</code>.
 177    */
 178   static native ThreadInfo getThreadInfoForId(long id, int maxDepth);
 179
 180   /**
 181    * Returns the number of nanoseconds of user time
 182    * the specified thread has used in total.   This is
 183    * only called if this feature is enabled and
 184    * supported.
 185    *
 186    * @param id the thread to obtain statistics on.
 187    * @return the nanoseconds of user time used by
 188    *         the thread.
 189    */
 190   static native long getThreadUserTime(long id);
 191
 192   /**
 193    * Returns the total number of threads that have
 194    * been started over the lifetime of the virtual
 195    * machine.
 196    *
 197    * @return the total number of threads started.
 198    */
 199   static native long getTotalStartedThreadCount();
 200
 201   /**
 202    * Resets the peak thread count to the current
 203    * number of live threads.
 204    */
 205   static native void resetPeakThreadCount();
 206
 207 }