/*
* 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:
*
* 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 io.netty_voltpatches.buffer;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import io.netty_voltpatches.util.internal.StringUtil;
import static java.lang.Math.*;
final class PoolChunkList<T> implements PoolChunkListMetric {
private static final Iterator<PoolChunkMetric> EMPTY_METRICS = Collections.<PoolChunkMetric>emptyList().iterator();
private final PoolChunkList<T> nextList;
private final int minUsage;
private final int maxUsage;
private final int maxCapacity;
private PoolChunk<T> head;
// 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(PoolChunkList<T> nextList, int minUsage, int maxUsage, int chunkSize) {
assert minUsage <= maxUsage;
this.nextList = nextList;
this.minUsage = minUsage;
this.maxUsage = maxUsage;
maxCapacity = calculateMaxCapacity(minUsage, chunkSize);
}
/**
* 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<T> prevList) {
assert this.prevList == null;
this.prevList = prevList;
}
boolean allocate(PooledByteBuf<T> buf, int reqCapacity, int normCapacity) {
if (head == null || 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<T> cur = head;;) {
long handle = cur.allocate(normCapacity);
if (handle < 0) {
cur = cur.next;
if (cur == null) {
return false;
}
} else {
cur.initBuf(buf, handle, reqCapacity);
if (cur.usage() >= maxUsage) {
remove(cur);
nextList.add(cur);
}
return true;
}
}
}
boolean free(PoolChunk<T> chunk, long handle) {
chunk.free(handle);
if (chunk.usage() < minUsage) {
remove(chunk);
// Move the PoolChunk down the PoolChunkList linked-list.
return move0(chunk);
}
return true;
}
private boolean move(PoolChunk<T> chunk) {
assert chunk.usage() < maxUsage;
if (chunk.usage() < minUsage) {
// 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<T> 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<T> chunk) {
if (chunk.usage() >= maxUsage) {
nextList.add(chunk);
return;
}
add0(chunk);
}
/**
* Adds the {@link PoolChunk} to this {@link PoolChunkList}.
*/
void add0(PoolChunk<T> 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<T> cur) {
if (cur == head) {
head = cur.next;
if (head != null) {
head.prev = null;
}
} else {
PoolChunk<T> 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<PoolChunkMetric> iterator() {
if (head == null) {
return EMPTY_METRICS;
}
List<PoolChunkMetric> metrics = new ArrayList<PoolChunkMetric>();
for (PoolChunk<T> cur = head;;) {
metrics.add(cur);
cur = cur.next;
if (cur == null) {
break;
}
}
return metrics.iterator();
}
@Override
public String toString() {
if (head == null) {
return "none";
}
StringBuilder buf = new StringBuilder();
for (PoolChunk<T> cur = head;;) {
buf.append(cur);
cur = cur.next;
if (cur == null) {
break;
}
buf.append(StringUtil.NEWLINE);
}
return buf.toString();
}
void destroy(PoolArena<T> arena) {
PoolChunk<T> chunk = head;
while (chunk != null) {
arena.destroyChunk(chunk);
chunk = chunk.next;
}
head = null;
}
}