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229 lines
8.4 KiB
229 lines
8.4 KiB
// serverMemory.java
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// -------------------------------------------
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// (C) 2005 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
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// first published 22.09.2005 on http://yacy.net
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//
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// $LastChangedDate$
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// $LastChangedRevision$
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// $LastChangedBy$
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//
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// LICENSE
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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package de.anomic.server;
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import de.anomic.server.logging.serverLog;
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import de.anomic.tools.yFormatter;
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/**
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* Use this to get information about memory usage or try to free some memory
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*/
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public class serverMemory {
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private static final Runtime runtime = Runtime.getRuntime();
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private static final serverLog log = new serverLog("MEMORY");
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private static final long[] gcs = new long[5];
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private static int gcs_pos = 0;
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private static long lastGC = 0l;
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/**
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* Runs the garbage collector if last garbage collection is more than last millis ago
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* @param last time which must be passed since lased gc
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* @param info additional info for log
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*/
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public final synchronized static void gc(int last, String info) { // thq
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long elapsed = System.currentTimeMillis() - lastGC;
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if (elapsed > last) {
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long free = free();
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System.gc();
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lastGC = System.currentTimeMillis();
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if (log.isFine()) log.logInfo("[gc] before: " + bytesToString(free) + ", after: " + bytesToString(free()) + ", call: " + info);
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} else if (log.isFine()) {
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if (log.isFinest()) log.logFinest("[gc] no execute, last run: " + (elapsed / 1000) + " seconds ago, call: " + info);
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}
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}
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/**
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* Tries to free count bytes
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* @param count bytes
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* @return the amount of freed bytes by a forced GC this method performes
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*/
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private static long runGC(final boolean count) {
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final long memBefore = available();
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gc(1000, "serverMemory.runGC(...)");
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final long freed = available() - memBefore;
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if (count) {
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gcs[gcs_pos] = freed;
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gcs_pos = (gcs_pos + 1) % gcs.length;
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}
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return freed;
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}
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/**
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* This method calculates the average amount of bytes freed by the last GCs forced by this class
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* @return the average amount of freed bytes of the last forced GCs or <code>0</code> if no
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* GC has been run yet
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*/
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public static long getAverageGCFree() {
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long x = 0;
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int y = 0;
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for (int i=0; i<gcs.length; i++)
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if (gcs[i] != 0) {
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x += gcs[i];
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y++;
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}
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return (y == 0) ? 0 : x / y;
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}
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/**
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* memory that is free without increasing of total memory taken from os
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* @return bytes
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*/
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public static final long free() {
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return runtime.freeMemory();
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}
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/**
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* memory that is available including increasing total memory up to maximum
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* @return bytes
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*/
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public static final long available() {
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return max() - total() + free();
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}
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/**
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* maximum memory which the vm can use
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* @return bytes
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*/
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public static final long max()
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{
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return runtime.maxMemory();
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}
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/**
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* currently allocated memory in the Java virtual machine; may vary over time
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* @return bytes
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*/
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public static final long total()
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{
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return runtime.totalMemory();
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}
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/**
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* <p>Tries to free a specified amount of bytes.</p>
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* <p>
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* If the currently available memory is enough, the method returns <code>true</code> without
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* performing additional steps. If not, the behaviour depends on the parameter <code>force</code>.
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* If <code>false</code>, a Full GC is only performed if former GCs indicated that a GC should
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* provide enough free memory. If former GCs didn't but <code>force</code> is set to <code>true</code>
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* a Full GC is performed nevertheless.
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* </p>
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* <p>
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* Setting the <code>force</code> parameter to false doesn't necessarily mean, that no GC may be
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* performed by this method, if the currently available memory doesn't suffice!
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* </p>
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* <p><em>Be careful with this method as GCs should always be the last measure to take</em></p>
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*
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* @param size the requested amount of free memory in bytes
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* @param force specifies whether a GC should be run even in case former GCs didn't provide enough memory
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* @return whether enough memory could be freed (or is free) or not
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*/
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public static boolean request(final long size, final boolean force) {
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long avail = available();
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if (avail >= size) return true;
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if (log.isFine()) {
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String t = new Throwable("Stack trace").getStackTrace()[1].toString();
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log.logFine(t + " requested " + (size >> 10) + " KB, got " + (avail >> 10) + " KB");
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}
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final long avg = getAverageGCFree();
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if (force || avg == 0 || avg + avail >= size) {
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// this is only called if we expect that an allocation of <size> bytes would cause the jvm to call the GC anyway
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final long freed = runGC(!force);
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avail = available();
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log.logInfo("performed " + ((force) ? "explicit" : "necessary") + " GC, freed " + (freed >> 10)
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+ " KB (requested/available/average: "
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+ (size >> 10) + " / " + (avail >> 10) + " / " + (avg >> 10) + " KB)");
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return avail >= size;
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} else {
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log.logInfo("former GCs indicate to not be able to free enough memory (requested/available/average: "
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+ (size >> 10) + " / " + (avail >> 10) + " / " + (avg >> 10) + " KB)");
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return false;
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}
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}
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/**
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* memory that is currently bound in objects
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* @return used bytes
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*/
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public static long used() {
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return total() - free();
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}
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/**
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* Formats a number if it are bytes to greatest unit (1024 based)
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* @param byteCount
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* @return formatted String with unit
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*/
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public static String bytesToString(long byteCount) {
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try {
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final StringBuffer byteString = new StringBuffer();
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if (byteCount > 1073741824) {
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byteString.append(yFormatter.number((double)byteCount / (double)1073741824 ))
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.append(" GB");
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} else if (byteCount > 1048576) {
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byteString.append(yFormatter.number((double)byteCount / (double)1048576))
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.append(" MB");
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} else if (byteCount > 1024) {
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byteString.append(yFormatter.number((double)byteCount / (double)1024))
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.append(" KB");
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} else {
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byteString.append(Long.toString(byteCount))
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.append(" Bytes");
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}
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return byteString.toString();
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} catch (Exception e) {
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return "unknown";
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}
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}
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/**
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* main
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* @param args
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*/
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public static void main(String[] args) {
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// try this with a jvm 1.4.2 and with a jvm 1.5 and compare results
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int mb = 1024 * 1024;
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System.out.println("vm: " + System.getProperty("java.vm.version"));
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System.out.println("computed max = " + (max() / mb) + " mb");
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int alloc = 10000;
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byte[][] x = new byte[100000][];
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for (int i = 0; i < 100000; i++) {
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x[i] = new byte[alloc];
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if (i % 100 == 0) System.out.println("used = " + (i * alloc / mb) +
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", total = " + (total() / mb) +
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", free = " + (free() / mb) +
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", max = " + (max() / mb) +
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", avail = " + (available() / mb));
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}
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}
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}
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