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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.cassandra.utils.memory;

import org.apache.cassandra.utils.concurrent.WaitQueue;

/**
 * A thread that reclaims memory from a MemtablePool on demand.  The actual reclaiming work is delegated to the
 * cleaner Runnable, e.g., FlushLargestColumnFamily
 */
class MemtableCleanerThread

extends Thread { /** The pool we're cleaning */ final P pool; /** should ensure that at least some memory has been marked reclaiming after completion */ final Runnable cleaner; /** signalled whenever needsCleaning() may return true */ final WaitQueue wait = new WaitQueue(); MemtableCleanerThread(P pool, Runnable cleaner) { super(pool.getClass().getSimpleName() + "Cleaner"); this.pool = pool; this.cleaner = cleaner; setDaemon(true); } boolean needsCleaning() { return pool.onHeap.needsCleaning() || pool.offHeap.needsCleaning(); } // should ONLY be called when we really think it already needs cleaning void trigger() { wait.signal(); } @Override public void run() { while (true) { while (!needsCleaning()) { final WaitQueue.Signal signal = wait.register(); if (!needsCleaning()) signal.awaitUninterruptibly(); else signal.cancel(); } cleaner.run(); } } }





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