io.netty.buffer.PoolChunkList Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
/*
* 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 implements PoolChunkListMetric {
private static final Iterator EMPTY_METRICS = Collections.emptyList().iterator();
private final PoolArena arena;
private final PoolChunkList nextList;
private final int minUsage;
private final int maxUsage;
private final int maxCapacity;
private PoolChunk 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 prevList;
// TODO: Test if adding padding helps under contention
//private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
PoolChunkList(PoolArena arena, PoolChunkList 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
//
// 2) usage() returns an int value and has a floor rounding during a calculation,
// to be aligned absolute thresholds should be shifted for "the rounding step":
// freeBytes * 100 / chunkSize < 1
// the condition can be converted to: freeBytes < 1 * chunkSize / 100
// this is why we have + 0.99999999 shifts. A example why just +1 shift cannot be used:
// freeBytes = 16777216 == freeMaxThreshold: 16777216, usage = 0 < minUsage: 1, chunkSize: 16777216
// At the same time we want to have zero thresholds in case of (maxUsage == 100) and (minUsage == 100).
//
freeMinThreshold = (maxUsage == 100) ? 0 : (int) (chunkSize * (100.0 - maxUsage + 0.99999999) / 100L);
freeMaxThreshold = (minUsage == 100) ? 0 : (int) (chunkSize * (100.0 - minUsage + 0.99999999) / 100L);
}
/**
* Calculates the maximum capacity of a buffer that will ever be possible to allocate out of the {@link PoolChunk}s
* that belong to the {@link PoolChunkList} with the given {@code minUsage} and {@code maxUsage} settings.
*/
private static int calculateMaxCapacity(int minUsage, int chunkSize) {
minUsage = minUsage0(minUsage);
if (minUsage == 100) {
// If the minUsage is 100 we can not allocate anything out of this list.
return 0;
}
// Calculate the maximum amount of bytes that can be allocated from a PoolChunk in this PoolChunkList.
//
// As an example:
// - If a PoolChunkList has minUsage == 25 we are allowed to allocate at most 75% of the chunkSize because
// this is the maximum amount available in any PoolChunk in this PoolChunkList.
return (int) (chunkSize * (100L - minUsage) / 100L);
}
void prevList(PoolChunkList prevList) {
assert this.prevList == null;
this.prevList = prevList;
}
boolean allocate(PooledByteBuf buf, int reqCapacity, int sizeIdx, PoolThreadCache threadCache) {
int normCapacity = arena.sizeClass.sizeIdx2size(sizeIdx);
if (normCapacity > maxCapacity) {
// Either this PoolChunkList is empty or the requested capacity is larger then the capacity which can
// be handled by the PoolChunks that are contained in this PoolChunkList.
return false;
}
for (PoolChunk cur = head; cur != null; cur = cur.next) {
if (cur.allocate(buf, reqCapacity, sizeIdx, threadCache)) {
if (cur.freeBytes <= freeMinThreshold) {
remove(cur);
nextList.add(cur);
}
return true;
}
}
return false;
}
boolean free(PoolChunk chunk, long handle, int normCapacity, ByteBuffer nioBuffer) {
chunk.free(handle, normCapacity, nioBuffer);
if (chunk.freeBytes > freeMaxThreshold) {
remove(chunk);
// Move the PoolChunk down the PoolChunkList linked-list.
return move0(chunk);
}
return true;
}
private boolean move(PoolChunk chunk) {
assert chunk.usage() < maxUsage;
if (chunk.freeBytes > freeMaxThreshold) {
// Move the PoolChunk down the PoolChunkList linked-list.
return move0(chunk);
}
// PoolChunk fits into this PoolChunkList, adding it here.
add0(chunk);
return true;
}
/**
* Moves the {@link PoolChunk} down the {@link PoolChunkList} linked-list so it will end up in the right
* {@link PoolChunkList} that has the correct minUsage / maxUsage in respect to {@link PoolChunk#usage()}.
*/
private boolean move0(PoolChunk chunk) {
if (prevList == null) {
// There is no previous PoolChunkList so return false which result in having the PoolChunk destroyed and
// all memory associated with the PoolChunk will be released.
assert chunk.usage() == 0;
return false;
}
return prevList.move(chunk);
}
void add(PoolChunk chunk) {
if (chunk.freeBytes <= freeMinThreshold) {
nextList.add(chunk);
return;
}
add0(chunk);
}
/**
* Adds the {@link PoolChunk} to this {@link PoolChunkList}.
*/
void add0(PoolChunk chunk) {
chunk.parent = this;
if (head == null) {
head = chunk;
chunk.prev = null;
chunk.next = null;
} else {
chunk.prev = null;
chunk.next = head;
head.prev = chunk;
head = chunk;
}
}
private void remove(PoolChunk cur) {
if (cur == head) {
head = cur.next;
if (head != null) {
head.prev = null;
}
} else {
PoolChunk next = cur.next;
cur.prev.next = next;
if (next != null) {
next.prev = cur.prev;
}
}
}
@Override
public int minUsage() {
return minUsage0(minUsage);
}
@Override
public int maxUsage() {
return min(maxUsage, 100);
}
private static int minUsage0(int value) {
return max(1, value);
}
@Override
public Iterator iterator() {
arena.lock();
try {
if (head == null) {
return EMPTY_METRICS;
}
List metrics = new ArrayList();
for (PoolChunk cur = head;;) {
metrics.add(cur);
cur = cur.next;
if (cur == null) {
break;
}
}
return metrics.iterator();
} finally {
arena.unlock();
}
}
@Override
public String toString() {
StringBuilder buf = new StringBuilder();
arena.lock();
try {
if (head == null) {
return "none";
}
for (PoolChunk cur = head;;) {
buf.append(cur);
cur = cur.next;
if (cur == null) {
break;
}
buf.append(StringUtil.NEWLINE);
}
} finally {
arena.unlock();
}
return buf.toString();
}
void destroy(PoolArena arena) {
PoolChunk chunk = head;
while (chunk != null) {
arena.destroyChunk(chunk);
chunk = chunk.next;
}
head = null;
}
}