com.lmax.disruptor.util.ThreadHints Maven / Gradle / Ivy
/* Copyright 2016 Gil Tene
*
* 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.util;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import static java.lang.invoke.MethodType.methodType;
/**
* This class captures possible hints that may be used by some
* runtimes to improve code performance. It is intended to capture hinting
* behaviours that are implemented in or anticipated to be spec'ed under the
* {@link java.lang.Thread} class in some Java SE versions, but missing in prior
* versions.
*/
public final class ThreadHints
{
private static final MethodHandle ON_SPIN_WAIT_METHOD_HANDLE;
static
{
final MethodHandles.Lookup lookup = MethodHandles.lookup();
MethodHandle methodHandle = null;
try
{
methodHandle = lookup.findStatic(Thread.class, "onSpinWait", methodType(void.class));
}
catch (final Exception ignore)
{
}
ON_SPIN_WAIT_METHOD_HANDLE = methodHandle;
}
private ThreadHints()
{
}
/**
* Indicates that the caller is momentarily unable to progress, until the
* occurrence of one or more actions on the part of other activities. By
* invoking this method within each iteration of a spin-wait loop construct,
* the calling thread indicates to the runtime that it is busy-waiting. The runtime
* may take action to improve the performance of invoking spin-wait loop constructions.
*/
public static void onSpinWait()
{
// Call java.lang.Thread.onSpinWait() on Java SE versions that support it. Do nothing otherwise.
// This should optimize away to either nothing or to an inlining of java.lang.Thread.onSpinWait()
if (null != ON_SPIN_WAIT_METHOD_HANDLE)
{
try
{
ON_SPIN_WAIT_METHOD_HANDLE.invokeExact();
}
catch (final Throwable ignore)
{
}
}
}
}