PoolChunkList.java — netty Source File

Source Code

/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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:
 *
 *   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 io.netty.buffer;

import io.netty.util.internal.StringUtil;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import static java.lang.Math.*;

import java.nio.ByteBuffer;

final class PoolChunkList<T> implements PoolChunkListMetric {
    private static final Iterator<PoolChunkMetric> EMPTY_METRICS = Collections.emptyIterator();
    private final PoolArena<T> arena;
    private final PoolChunkList<T> nextList;
    private final int minUsage;
    private final int maxUsage;
    private final int maxCapacity;
    private PoolChunk<T> head;
    private final int freeMinThreshold;
    private final int freeMaxThreshold;

    // This is only update once when create the linked like list of PoolChunkList in PoolArena constructor.
    private PoolChunkList<T> prevList;

    // TODO: Test if adding padding helps under contention
    //private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;

    PoolChunkList(PoolArena<T> arena, PoolChunkList<T> nextList, int minUsage, int maxUsage, int chunkSize) {
        assert minUsage <= maxUsage;
        this.arena = arena;
        this.nextList = nextList;
        this.minUsage = minUsage;
        this.maxUsage = maxUsage;
        maxCapacity = calculateMaxCapacity(minUsage, chunkSize);

        // the thresholds are aligned with PoolChunk.usage() logic:
        // 1) basic logic: usage() = 100 - freeBytes * 100L / chunkSize
        //    so, for example: (usage() >= maxUsage) condition can be transformed in the following way:
        //      100 - freeBytes * 100L / chunkSize >= maxUsage
        //      freeBytes <= chunkSize * (100 - maxUsage) / 100
        //      let freeMinThreshold = chunkSize * (100 - maxUsage) / 100, then freeBytes <= freeMinThreshold
// ... (203 more lines)