com.fluxtion.agrona.concurrent.IdleStrategy Maven / Gradle / Ivy
/*
* Copyright 2014-2024 Real Logic Limited.
*
* 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
*
* https://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.fluxtion.agrona.concurrent;
/**
* Idle strategy for use by threads when they do not have work to do.
*
* Note regarding implementor state
*
* Some implementations are known to be stateful, please note that you cannot safely assume implementations to be
* stateless. Where implementations are stateful it is recommended that implementation state is padded to avoid false
* sharing.
*
* Note regarding potential for TTSP(Time To Safe Point) issues
*
* If the caller spins in a 'counted' loop, and the implementation does not include a safepoint poll this may cause a
* TTSP (Time To SafePoint) problem. If this is the case for your application you can solve it by preventing the idle
* method from being inlined by using a Hotspot compiler command as a JVM argument e.g:
* -XX:CompileCommand=dontinline,com.fluxtion.agrona.concurrent.NoOpIdleStrategy::idle
*/
public interface IdleStrategy
{
/**
* Perform current idle action (e.g. nothing/yield/sleep). This method signature expects users to call into it on
* every work 'cycle'. The implementations may use the indication "workCount > 0" to reset internal backoff
* state. This method works well with 'work' APIs which follow the following rules:
*
* - 'work' returns a value larger than 0 when some work has been done
* - 'work' returns 0 when no work has been done
* - 'work' may return error codes which are less than 0, but which amount to no work has been done
*
*
* Callers are expected to follow this pattern:
*
*
*
* while (isRunning)
* {
* idleStrategy.idle(doWork());
* }
*
*
*
* @param workCount performed in last duty cycle.
*/
void idle(int workCount);
/**
* Perform current idle action (e.g. nothing/yield/sleep). To be used in conjunction with
* {@link IdleStrategy#reset()} to clear internal state when idle period is over (or before it begins).
* Callers are expected to follow this pattern:
*
*
*
* while (isRunning)
* {
* if (!hasWork())
* {
* idleStrategy.reset();
* while (!hasWork())
* {
* if (!isRunning)
* {
* return;
* }
* idleStrategy.idle();
* }
* }
* doWork();
* }
*
*
*/
void idle();
/**
* Reset the internal state in preparation for entering an idle state again.
*/
void reset();
/**
* Simple name by which the strategy can be identified.
*
* @return simple name by which the strategy can be identified.
*/
default String alias()
{
return "";
}
}