/*
 * Copyright (c) 2014, 2015, Dynatrace and/or its affiliates. All rights reserved.
 * 
 * This file is part of the Lock Contention Tracing Subsystem for the HotSpot
 * Virtual Machine, which is developed at Christian Doppler Laboratory on
 * Monitoring and Evolution of Very-Large-Scale Software Systems. Please
 * contact us at <http://mevss.jku.at/> if you need additional information
 * or have any questions.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work. If not, see <http://www.gnu.org/licenses/>.
 *
 */ 
package sun.evtracing.processing.statistics.aggregator;

import sun.evtracing.processing.Sanity;
import sun.evtracing.processing.statistics.metadata.Contention;

public class NegativeDurationContentionFilter implements ContentionProcessor {

    private final ContentionProcessor delegate;

    public NegativeDurationContentionFilter(ContentionProcessor delegate) {
        this.delegate = delegate;
    }

    @Override
    public void submit(Contention c) {
        if (c.duration >= 0) {
            delegate.submit(c);
        } else {
            // The participating threads typically execute on different CPUs. The
            // clocks of different CPUs are always slightly out of sync, which
            // results in some error. In some cases, this causes small durations to
            // become negative.

            // TODO: filtering negative durations is ok for computing sums, but for
            // correct counts and averages, we need to find a way to deal with them.

            if (c.duration < -1000000) {
                Sanity.warn("dropped contention with negative duration above 1ms: %.3f ms", c.duration / (1000.f * 1000));
            } else {
                Sanity.warn("dropped contention with negative duration in sub-millisecond range: %.3f us", c.duration);
            }
        }
    }

    @Override
    public void merge() {
        delegate.merge();
    }

}