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224 lines
8.2 KiB
224 lines
8.2 KiB
// MemoryControl.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: 2011-08-18 00:24:17 +0200 (Do, 18. Aug 2011) $
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// $LastChangedRevision: 7883 $
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// $LastChangedBy: orbiter $
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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 net.yacy.kelondro.util;
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/**
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* Standard implementation to get information about memory usage or try to free some memory
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*/
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public class StandardMemoryStrategy extends MemoryStrategy {
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private final Runtime runtime = Runtime.getRuntime();
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private final long[] gcs = new long[5];
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private int gcs_pos = 0;
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private long properMbyte = 0L;
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private long prevTreshold = 0L;
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private int tresholdCount = 0;
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private boolean proper = true;
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public StandardMemoryStrategy() {
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name = "Standard Memory Strategy";
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error= false; //since this is the standard implementation we assume always false here
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}
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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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protected final synchronized boolean gc(final int last, final String info) { // thq
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assert last >= 10000; // too many forced GCs will cause bad execution performance
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final long elapsed = System.currentTimeMillis() - lastGC;
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if (elapsed > last) {
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final long before = free();
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final long start = System.currentTimeMillis();
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System.gc();
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lastGC = System.currentTimeMillis();
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final long after = free();
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gcs[gcs_pos++] = after - before;
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if (gcs_pos >= gcs.length) gcs_pos = 0;
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if (log.isFine()) log.logInfo("[gc] before: " + Formatter.bytesToString(before) +
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", after: " + Formatter.bytesToString(after) +
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", freed: " + Formatter.bytesToString(after - before) +
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", rt: " + (lastGC - start) + " ms, call: " + info);
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return true;
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}
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if (log.isFinest()) log.logFinest("[gc] no execute, last run: " + (elapsed / 1000) + " seconds ago, call: " + info);
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return false;
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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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protected final long getAverageGCFree() {
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long x = 0;
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int y = 0;
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for (final long gc : gcs)
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if (gc != 0) {
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x += gc;
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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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protected 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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protected final long available() {
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return maxMemory() - total() + free();
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}
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/**
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* maximum memory the Java virtual will allocate machine; may vary over time in some cases
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* @return bytes
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*/
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protected final long maxMemory()
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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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protected 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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protected boolean request(final long size, final boolean force, boolean shortStatus) {
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if (size <= 0) return true;
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final boolean r = request0(size, force);
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shortStatus = !r;
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return r;
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}
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private boolean request0(final long size, final boolean force) {
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final long avg = getAverageGCFree();
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if (avg >= size) return true;
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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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final 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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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 memBefore = avail;
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final boolean performedGC = gc(10000, "serverMemory.runGC(...)");
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avail = available();
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if (performedGC) {
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final long freed = avail - memBefore;
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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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}
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checkProper(avail);
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return avail >= size;
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} else {
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if (log.isFine()) log.logFine("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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protected final long used() {
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return total() - free();
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}
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protected boolean properState() {
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return proper;
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}
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protected void resetProperState() {
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proper = true;
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tresholdCount = 0;
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}
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/**
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* set the memory to be available
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*/
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protected void setProperMbyte(final long mbyte) {
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properMbyte = mbyte;
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tresholdCount = 0;
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}
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private void checkProper(final long available) {
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// disable proper state if memory is less than treshold - 4 times, maximum 11 minutes between each detection
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if ((available >> 20) < properMbyte) {
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final long t = System.currentTimeMillis();
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if(prevTreshold + 11L /* minutes */ * 60000L > t) {
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tresholdCount++;
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if(tresholdCount > 3 /* occurencies - 1 */) proper = false;
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}
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else tresholdCount = 1;
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prevTreshold = t;
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log.logInfo("checkProper: below treshold; tresholdCount: " + tresholdCount + "; proper: " + proper);
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}
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else if (!proper && (available >> 20) > (properMbyte * 2L)) // we were wrong!
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resetProperState();
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}
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}
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