001/* 002 * This file is part of the Jikes RVM project (http://jikesrvm.org). 003 * 004 * This file is licensed to You under the Eclipse Public License (EPL); 005 * You may not use this file except in compliance with the License. You 006 * may obtain a copy of the License at 007 * 008 * http://www.opensource.org/licenses/eclipse-1.0.php 009 * 010 * See the COPYRIGHT.txt file distributed with this work for information 011 * regarding copyright ownership. 012 */ 013package org.jikesrvm.adaptive.measurements.listeners; 014 015import org.jikesrvm.VM; 016import org.jikesrvm.scheduler.RVMThread; 017import org.vmmagic.pragma.Uninterruptible; 018 019/** 020 * A simple listener to accumulate counts of total events 021 * and the fraction of those events that occurred at loop backedges. 022 * In effect, this provides a mechanism for estimating the 023 * call density of the program. If most yieldpoints are being taken at 024 * backedges, then call density is low. 025 */ 026@Uninterruptible 027public final class CallDensityListener extends NullListener { 028 029 private double numSamples = 0; 030 private double numBackedgeSamples = 0; 031 032 @Override 033 public void update(int whereFrom) { 034 numSamples++; 035 if (whereFrom == RVMThread.BACKEDGE) numBackedgeSamples++; 036 } 037 038 public double callDensity() { 039 return 1 - (numBackedgeSamples / numSamples); 040 } 041 042 @Override 043 public void reset() { 044 numSamples = 0; 045 numBackedgeSamples = 0; 046 } 047 048 @Override 049 public void report() { 050 VM.sysWriteln("The call density of the program is ", callDensity()); 051 } 052}