com.lmax.disruptor.SleepingWaitStrategy Maven / Gradle / Ivy
/*
* Copyright 2011 LMAX Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.lmax.disruptor;
import java.util.concurrent.locks.LockSupport;
/**
* Sleeping strategy that initially spins, then uses a Thread.yield(), and
* eventually sleep (LockSupport.parkNanos(n)) for the minimum
* number of nanos the OS and JVM will allow while the
* {@link com.lmax.disruptor.EventProcessor}s are waiting on a barrier.
*
* This strategy is a good compromise between performance and CPU resource.
* Latency spikes can occur after quiet periods. It will also reduce the impact
* on the producing thread as it will not need signal any conditional variables
* to wake up the event handling thread.
*/
public final class SleepingWaitStrategy implements WaitStrategy
{
private static final int DEFAULT_RETRIES = 200;
private static final long DEFAULT_SLEEP = 100;
private final int retries;
private final long sleepTimeNs;
public SleepingWaitStrategy()
{
this(DEFAULT_RETRIES, DEFAULT_SLEEP);
}
public SleepingWaitStrategy(int retries)
{
this(retries, DEFAULT_SLEEP);
}
public SleepingWaitStrategy(int retries, long sleepTimeNs)
{
this.retries = retries;
this.sleepTimeNs = sleepTimeNs;
}
@Override
public long waitFor(
final long sequence, Sequence cursor, final Sequence dependentSequence, final SequenceBarrier barrier)
throws AlertException
{
long availableSequence;
int counter = retries;
while ((availableSequence = dependentSequence.get()) < sequence)
{
counter = applyWaitMethod(barrier, counter);
}
return availableSequence;
}
@Override
public void signalAllWhenBlocking()
{
}
private int applyWaitMethod(final SequenceBarrier barrier, int counter)
throws AlertException
{
barrier.checkAlert();
if (counter > 100)
{
--counter;
}
else if (counter > 0)
{
--counter;
Thread.yield();
}
else
{
LockSupport.parkNanos(sleepTimeNs);
}
return counter;
}
}