// MemoryControl.java
// -------------------------------------------
// (C) 2005 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
// first published 22.09.2005 on http://yacy.net
//
// $LastChangedDate: 2011-08-18 00:24:17 +0200 (Do, 18. Aug 2011) $
// $LastChangedRevision: 7883 $
// $LastChangedBy: orbiter $
//
// LICENSE
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package net.yacy.kelondro.util;
/**
* Standard implementation to get information about memory usage or try to free some memory
*/
public class StandardMemoryStrategy extends MemoryStrategy {
private final Runtime runtime = Runtime.getRuntime();
private final long[] gcs = new long[5];
private int gcs_pos = 0;
private long properMbyte = 0L;
private long prevTreshold = 0L;
private int tresholdCount = 0;
private boolean proper = true;
public StandardMemoryStrategy() {
name = "Standard Memory Strategy";
error= false; //since this is the standard implementation we assume always false here
}
/**
* Runs the garbage collector if last garbage collection is more than last millis ago
* @param last time which must be passed since lased gc
* @param info additional info for log
*/
protected final synchronized boolean gc(final int last, final String info) { // thq
assert last >= 10000; // too many forced GCs will cause bad execution performance
final long elapsed = System.currentTimeMillis() - lastGC;
if (elapsed > last) {
final long before = free();
final long start = System.currentTimeMillis();
System.gc();
lastGC = System.currentTimeMillis();
final long after = free();
gcs[gcs_pos++] = after - before;
if (gcs_pos >= gcs.length) gcs_pos = 0;
if (log.isFine()) log.logInfo("[gc] before: " + Formatter.bytesToString(before) +
", after: " + Formatter.bytesToString(after) +
", freed: " + Formatter.bytesToString(after - before) +
", rt: " + (lastGC - start) + " ms, call: " + info);
return true;
}
if (log.isFinest()) log.logFinest("[gc] no execute, last run: " + (elapsed / 1000) + " seconds ago, call: " + info);
return false;
}
/**
* This method calculates the average amount of bytes freed by the last GCs forced by this class
* @return the average amount of freed bytes of the last forced GCs or 0 if no
* GC has been run yet
*/
protected final long getAverageGCFree() {
long x = 0;
int y = 0;
for (final long gc : gcs)
if (gc != 0) {
x += gc;
y++;
}
return (y == 0) ? 0 : x / y;
}
/**
* memory that is free without increasing of total memory taken from os
* @return bytes
*/
protected final long free() {
return runtime.freeMemory();
}
/**
* memory that is available including increasing total memory up to maximum
* @return bytes
*/
protected final long available() {
return maxMemory() - total() + free();
}
/**
* maximum memory the Java virtual will allocate machine; may vary over time in some cases
* @return bytes
*/
protected final long maxMemory()
{
return runtime.maxMemory();
}
/**
* currently allocated memory in the Java virtual machine; may vary over time
* @return bytes
*/
protected final long total()
{
return runtime.totalMemory();
}
/**
* Tries to free a specified amount of bytes.
*
* If the currently available memory is enough, the method returns true without
* performing additional steps. If not, the behaviour depends on the parameter force.
* If false, a Full GC is only performed if former GCs indicated that a GC should
* provide enough free memory. If former GCs didn't but force is set to true
* a Full GC is performed nevertheless.
*
*
* Setting the force parameter to false doesn't necessarily mean, that no GC may be
* performed by this method, if the currently available memory doesn't suffice!
*
* Be careful with this method as GCs should always be the last measure to take
*
* @param size the requested amount of free memory in bytes
* @param force specifies whether a GC should be run even in case former GCs didn't provide enough memory
* @return whether enough memory could be freed (or is free) or not
*/
protected boolean request(final long size, final boolean force, boolean shortStatus) {
if (size <= 0) return true;
final boolean r = request0(size, force);
shortStatus = !r;
return r;
}
private boolean request0(final long size, final boolean force) {
final long avg = getAverageGCFree();
if (avg >= size) return true;
long avail = available();
if (avail >= size) return true;
if (log.isFine()) {
final String t = new Throwable("Stack trace").getStackTrace()[1].toString();
log.logFine(t + " requested " + (size >> 10) + " KB, got " + (avail >> 10) + " KB");
}
if (force || avg == 0 || avg + avail >= size) {
// this is only called if we expect that an allocation of bytes would cause the jvm to call the GC anyway
final long memBefore = avail;
final boolean performedGC = gc(10000, "serverMemory.runGC(...)");
avail = available();
if (performedGC) {
final long freed = avail - memBefore;
log.logInfo("performed " + ((force) ? "explicit" : "necessary") + " GC, freed " + (freed >> 10)
+ " KB (requested/available/average: "
+ (size >> 10) + " / " + (avail >> 10) + " / " + (avg >> 10) + " KB)");
}
checkProper(avail);
return avail >= size;
} else {
if (log.isFine()) log.logFine("former GCs indicate to not be able to free enough memory (requested/available/average: "
+ (size >> 10) + " / " + (avail >> 10) + " / " + (avg >> 10) + " KB)");
return false;
}
}
/**
* memory that is currently bound in objects
* @return used bytes
*/
protected final long used() {
return total() - free();
}
protected boolean properState() {
return proper;
}
protected void resetProperState() {
proper = true;
tresholdCount = 0;
}
/**
* set the memory to be available
*/
protected void setProperMbyte(final long mbyte) {
properMbyte = mbyte;
tresholdCount = 0;
}
private void checkProper(final long available) {
// disable proper state if memory is less than treshold - 4 times, maximum 11 minutes between each detection
if ((available >> 20) < properMbyte) {
final long t = System.currentTimeMillis();
if(prevTreshold + 11L /* minutes */ * 60000L > t) {
tresholdCount++;
if(tresholdCount > 3 /* occurencies - 1 */) proper = false;
}
else tresholdCount = 1;
prevTreshold = t;
log.logInfo("checkProper: below treshold; tresholdCount: " + tresholdCount + "; proper: " + proper);
}
else if (!proper && (available >> 20) > (properMbyte * 2L)) // we were wrong!
resetProperState();
}
}