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/*
* Copyright (C) 2020 ActiveJ LLC.
*
* 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
*
* 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.activej.bytebuf;
import io.activej.bytebuf.ByteBuf.ByteBufSlice;
import io.activej.common.ApplicationSettings;
import io.activej.common.MemSize;
import io.activej.common.concurrent.ObjectPool;
import java.lang.StackWalker.StackFrame;
import java.time.Duration;
import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;
import static io.activej.common.Checks.checkArgument;
import static java.lang.Integer.numberOfLeadingZeros;
import static java.lang.Math.max;
import static java.lang.System.currentTimeMillis;
import static java.util.Arrays.stream;
import static java.util.Comparator.comparingLong;
import static java.util.stream.Collectors.toList;
/**
* Represents a pool of ByteBufs with 33 slabs. Each of these slabs
* is a {@code ByteBufConcurrentStack} which stores ByteBufs of a
* particular capacity which is a power of two.
*
* When you need a new ByteBuf, it is either created (if a ByteBuf of
* such capacity hasn't been used and recycled yet) or popped from the
* appropriate slabs' stack.
*/
@SuppressWarnings({"WeakerAccess", "unused"})
public final class ByteBufPool {
private static final int NUMBER_OF_SLABS = 33;
/**
* Defines the minimal size of ByteBufs in this ByteBufPool.
* A constant value, by default set at 0.
*/
private static final int MIN_SIZE = ApplicationSettings.getMemSize(ByteBufPool.class, "minSize", MemSize.ZERO).toInt();
/**
* Defines the maximum size of ByteBufs in this ByteBufPool.
* A constant value, by default set at 0.
*/
private static final int MAX_SIZE = ApplicationSettings.getMemSize(ByteBufPool.class, "maxSize", MemSize.ZERO).toInt();
private static final boolean MIN_MAX_CHECKS = MIN_SIZE != 0 || MAX_SIZE != 0;
/**
* Allows getting trace stack about {@code ByteBufs} of this {@code ByteBufPool}
* while debugging if set at value {@code true} (note that this is resource intensive).
* By default, set at value {@code false}. If changed, significantly
* influences the performance and workflow of {@link #allocate(int)} operation.
*/
static final boolean REGISTRY = ApplicationSettings.getBoolean(ByteBufPool.class, "registry", false);
/**
* Allows getting statistics about this ByteBufPool while debugging
* if set at value {@code true} (note that this is resource intensive).
* By default, set at value {@code false}. If changed, significantly
* influences the performance and workflow of {@link #allocate(int)} operation.
*/
static final boolean STATS = ApplicationSettings.getBoolean(ByteBufPool.class, "stats", false);
/**
* Allows clearing byte bufs when being returned to the pool
* if set at value {@code true} (note that this is resource intensive).
* By default, set at value {@code false}. If changed,
* influences the performance of {@link #recycle(ByteBuf)} operation.
* Should only be used for testing to catch bugs with premature {@link ByteBuf} recycling,
* should not be used in production code
*/
static final boolean CLEAR_ON_RECYCLE = ApplicationSettings.getBoolean(ByteBufPool.class, "clearOnRecycle", false);
static final boolean USE_WATCHDOG = ApplicationSettings.getBoolean(ByteBufPool.class, "useWatchdog", false);
static final Duration WATCHDOG_INTERVAL = ApplicationSettings.getDuration(ByteBufPool.class, "watchdogInterval", Duration.ofSeconds(2));
static final Duration WATCHDOG_SMOOTHING_WINDOW = ApplicationSettings.getDuration(ByteBufPool.class, "watchdogSmoothingWindow", Duration.ofSeconds(10));
static final double WATCHDOG_ERROR_MARGIN = ApplicationSettings.getDouble(ByteBufPool.class, "watchdogErrorMargin", 4.0);
private static final double SMOOTHING_COEFF = 1.0 - Math.pow(0.5, (double) WATCHDOG_INTERVAL.toMillis() / WATCHDOG_SMOOTHING_WINDOW.toMillis());
/**
* {@code ByteBufConcurrentStack} allows working with slabs and their ByteBufs.
* Basically, it is a singly linked list with basic stack operations:
* {@code push, pop, peek, clear, isEmpty, size}.
*
* The implementation of {@code ByteBufConcurrentStack} is highly efficient
* due to utilizing {@link java.util.concurrent.atomic.AtomicReference}.
* Moreover, such approach allows working with slabs concurrently safely.
*/
static final ObjectPool[] slabs;
static final SlabStats[] slabStats;
static final AtomicInteger[] created;
static final AtomicInteger[] reused;
private static final ByteBufPoolStats stats = new ByteBufPoolStats();
/**
* Stores information about ByteBufs for stats.
*
* It is a helper class which contains size,
* timestamp and stackTrace which represent
* information about the ByteBufs.
*/
public static final class Entry {
final int size;
final long timestamp;
final Thread thread;
final List stackTrace;
Entry(int size, long timestamp, Thread thread, List stackTrace) {
this.size = size;
this.timestamp = timestamp;
this.thread = thread;
this.stackTrace = stackTrace;
}
public int getSize() {
return size;
}
public long getTimestamp() {
return timestamp;
}
public String getAge() {
return Duration.ofMillis(System.currentTimeMillis() - timestamp).toString();
}
public String getThread() {
return thread.toString();
}
public List getStackTrace() {
return stackTrace.stream().map(Object::toString).toList();
}
@Override
public String toString() {
return
"{" +
"size=" + size +
", timestamp=" + timestamp +
", thread=" + thread +
", stackTrace=" + stackTrace +
'}';
}
}
private static final Map allocateRegistry = Collections.synchronizedMap(new WeakHashMap<>());
private static final Map recycleRegistry = Collections.synchronizedMap(new WeakHashMap<>());
static {
slabs = new ObjectPool[NUMBER_OF_SLABS];
slabStats = new SlabStats[NUMBER_OF_SLABS];
created = new AtomicInteger[NUMBER_OF_SLABS];
reused = new AtomicInteger[NUMBER_OF_SLABS];
for (int i = 0; i < NUMBER_OF_SLABS; i++) {
slabs[i] = new ObjectPool<>();
created[i] = new AtomicInteger();
reused[i] = new AtomicInteger();
}
if (USE_WATCHDOG) {
for (int i = 0; i < NUMBER_OF_SLABS; i++) {
slabStats[i] = new SlabStats();
}
Thread watchdogThread = new Thread(() -> {
while (true) {
updateStats();
evict();
try {
//noinspection BusyWait
Thread.sleep(WATCHDOG_INTERVAL.toMillis());
} catch (InterruptedException ignored) {
Thread.currentThread().interrupt();
break;
}
}
}, "bytebufpool-watchdog-thread");
watchdogThread.setDaemon(true);
watchdogThread.setPriority(Thread.MIN_PRIORITY);
watchdogThread.start();
}
}
private ByteBufPool() {}
/**
* Allocates byte buffer from the pool with size of
* ceil(log2(size))2
* (rounds up to the nearest power of 2) bytes.
*
* Note that resource intensive {@link #buildRegistryEntry(ByteBuf)} will be executed
* only if {{@code #REGISTRY}} is set {@code true}. Also, such parameters as
* {@code STATS}, {@code MIN_MAX_CHECKS}, {@code MIN_SIZE}, {@code MAX_SIZE}
* significantly influence the workflow of the {@code allocate} operation.
*
* @param size returned byte buffer size is guaranteed to be bigger or equal to requested size
* @return byte buffer from this pool
*/
public static ByteBuf allocate(int size) {
assert size >= 0 : "Allocating ByteBuf with negative size";
if (MIN_MAX_CHECKS) {
if ((MIN_SIZE != 0 && size < MIN_SIZE) || (MAX_SIZE != 0 && size >= MAX_SIZE)) {
// not willing to register in pool
return ByteBuf.wrapForWriting(new byte[size]);
}
}
int index = 32 - numberOfLeadingZeros(size - 1); // index==32 for size==0
ObjectPool slab = slabs[index];
ByteBuf buf = slab.poll();
if (buf != null) {
if (USE_WATCHDOG) {
int slabSize = slab.size();
//noinspection NonAtomicOperationOnVolatileField
slabStats[index].min = Math.min(slabStats[index].min, slabSize);
}
if (ByteBuf.CHECK_RECYCLE && buf.refs != -1) throw onByteBufRecycled(buf);
buf.tail = 0;
buf.head = 0;
buf.refs = 1;
if (STATS) recordReuse(index);
} else {
if (USE_WATCHDOG) slabStats[index].min = 0;
buf = ByteBuf.wrapForWriting(new byte[index == 32 ? 0 : 1 << index]);
buf.refs = 1;
if (STATS) recordNew(index);
}
if (REGISTRY) allocateRegistry.put(buf, buildRegistryEntry(buf));
return buf;
}
private static void recordNew(int index) {
created[index].incrementAndGet();
}
private static void recordReuse(int index) {
reused[index].incrementAndGet();
}
private static Entry buildRegistryEntry(ByteBuf buf) {
return new Entry(buf.array.length, currentTimeMillis(), Thread.currentThread(),
StackWalker.getInstance().walk(frames -> frames.skip(3).toList()));
}
static AssertionError onByteBufRecycled(ByteBuf buf) {
int slab = 32 - numberOfLeadingZeros(buf.array.length - 1);
ObjectPool pool = slabs[slab];
pool.clear();
if (USE_WATCHDOG) slabStats[slab].clear();
return new AssertionError(
"Attempt to use recycled ByteBuf" +
(REGISTRY ? ByteBufPool.getByteBufTrace(buf) : ""));
}
static String getByteBufTrace(ByteBuf buf) {
Entry allocated = allocateRegistry.get(buf);
Entry recycled = recycleRegistry.get(buf);
if (allocated == null && recycled == null) return "";
return
"\nAllocated: " + allocated +
"\nRecycled: " + recycled;
}
/**
* Allocates byte buffer in the same way as {@link #allocate(int)} does, but
* sets its positions so that write-remaining is equal to requested size.
*
* For example, if you need a {@code ByteBuf} of size 21,
* a {@code ByteBuf} of size 32 is allocated. (|______|)
* But its read/write positions are set to 11 so that only last 21 are writable (|__####|)
*
*
* @param size requested size
* @return byte buffer from this pool with appropriate positions set
*/
public static ByteBuf allocateExact(int size) {
ByteBuf buf = allocate(size);
int d = buf.writeRemaining() - size;
buf.tail(d);
buf.head(d);
return buf;
}
public static ByteBuf allocate(MemSize size) {
return allocate(size.toInt());
}
public static ByteBuf allocateExact(MemSize size) {
return allocateExact(size.toInt());
}
/**
* Returns provided ByteBuf to the ByteBufPool to the appropriate slab.
*
* @param buf the ByteBuf to be recycled
*/
static void recycle(ByteBuf buf) {
int slab = 32 - numberOfLeadingZeros(buf.array.length - 1);
ObjectPool pool = slabs[slab];
if (CLEAR_ON_RECYCLE) Arrays.fill(buf.array(), (byte) 0);
if (REGISTRY) {
recycleRegistry.put(buf, buildRegistryEntry(buf));
allocateRegistry.remove(buf);
}
pool.offer(buf);
}
public static ByteBuf ensureWriteRemaining(ByteBuf buf, int newWriteRemaining) {
return ensureWriteRemaining(buf, 0, newWriteRemaining);
}
/**
* Checks if current ByteBuf can accommodate the needed
* amount of writable bytes.
*
* Returns this ByteBuf, if it contains enough writable bytes.
*
* Otherwise, creates a new ByteBuf which contains data from the
* original ByteBuf and fits the parameters. Then recycles the
* original ByteBuf.
*
* @param buf the ByteBuf to check
* @param minSize the minimal size of the ByteBuf
* @param newWriteRemaining amount of needed writable bytes
* @return a ByteBuf which fits the parameters
*/
public static ByteBuf ensureWriteRemaining(ByteBuf buf, int minSize, int newWriteRemaining) {
if (newWriteRemaining == 0) return buf;
if (buf.writeRemaining() < newWriteRemaining || buf instanceof ByteBufSlice) {
ByteBuf newBuf = allocate(max(minSize, newWriteRemaining + buf.readRemaining()));
newBuf.put(buf);
buf.recycle();
return newBuf;
}
return buf;
}
/**
* Appends one ByteBuf to another ByteBuf. If target ByteBuf
* can't accommodate the ByteBuf to be appended, a new ByteBuf
* is created which contains both target and source ByteBufs data.
* The source ByteBuf is recycled after append.
*
* If target ByteBuf has no readable bytes, it is being recycled
* and the source ByteBuf is returned.
*
* Both ByteBufs must be not recycled before the operation.
*
* @param to the target ByteBuf to which another ByteBuf will be appended
* @param from the source ByteBuf to be appended
* @return ByteBuf which contains the result of the appending
*/
public static ByteBuf append(ByteBuf to, ByteBuf from) {
checkArgument(!to.isRecycled() && !from.isRecycled());
if (to.readRemaining() == 0) {
to.recycle();
return from;
}
to = ensureWriteRemaining(to, from.readRemaining());
to.put(from);
from.recycle();
return to;
}
/**
* Appends byte array to ByteBuf. If ByteBuf can't accommodate the
* byte array, a new ByteBuf is created which contains all data from
* the original ByteBuf and has enough capacity to accommodate the
* byte array.
*
* ByteBuf must be not recycled before the operation.
*
* @param to the target ByteBuf to which byte array will be appended
* @param from the source byte array to be appended
* @param offset the value of offset for the byte array
* @param length amount of the bytes to be appended to the ByteBuf
* The sum of the length and offset parameters can't
* be greater than the whole length of the byte array
* @return ByteBuf which contains the result of the appending
*/
public static ByteBuf append(ByteBuf to, byte[] from, int offset, int length) {
checkArgument(!to.isRecycled());
to = ensureWriteRemaining(to, length);
to.put(from, offset, length);
return to;
}
public static ByteBuf append(ByteBuf to, byte[] from) {
return append(to, from, 0, from.length);
}
/**
* Clears all the slabs and stats.
*/
public static void clear() {
for (int i = 0; i < ByteBufPool.NUMBER_OF_SLABS; i++) {
slabs[i].clear();
created[i].set(0);
reused[i].set(0);
if (USE_WATCHDOG) slabStats[i].clear();
}
allocateRegistry.clear();
recycleRegistry.clear();
}
public static ByteBufPoolStats getStats() {
return stats;
}
public interface ByteBufPoolStatsMXBean {
int getCreatedItems();
int getReusedItems();
int getPoolItems();
long getPoolSize();
long getPoolSizeKB();
long getTotalSlabMins();
long getTotalEvicted();
List getPoolSlabs();
List queryUnrecycledBufs(int limit);
void clear();
void clearRegistry();
}
/**
* Manages stats for this {@link ByteBufPool}. You can get the
* amount of created and reused ByteBufs and amount of ByteBufs
* stored in each of the slabs.
*
* Also, you can get a String which contains information about
* amount of created and stored in pool ByteBufs.
*
* For memory control, you can get the size of your ByteBufPool in
* Byte or KB as well as get information about the slabs themselves
* (size, amount of ByteBufs created, reused, stored in pool, and
* total size in KB) and unrecycled ByteBufs.
*
* Finally, it allows to clear this ByteBufPool and its registry.
*/
public static final class ByteBufPoolStats implements ByteBufPoolStatsMXBean {
@Override
public int getCreatedItems() {
return stream(created).mapToInt(AtomicInteger::get).sum();
}
@Override
public int getReusedItems() {
return stream(reused).mapToInt(AtomicInteger::get).sum();
}
@Override
public int getPoolItems() {
return stream(slabs).mapToInt(ObjectPool::size).sum();
}
@SuppressWarnings("StringConcatenationInsideStringBufferAppend")
public String getPoolItemsString() {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < ByteBufPool.NUMBER_OF_SLABS; ++i) {
int createdItems = created[i].get();
int poolItems = slabs[i].size();
if (createdItems != poolItems) {
sb.append(String.format("Slab %d (%d) ", i, (1 << i)))
.append(" created: " + createdItems)
.append(" pool: " + poolItems + "\n");
}
}
return sb.toString();
}
@Override
public long getPoolSize() {
long result = 0;
for (int i = 0; i < slabs.length - 1; i++) {
long slabSize = 1L << i;
result += slabSize * slabs[i].size();
}
return result;
}
@Override
public long getPoolSizeKB() {
return getPoolSize() / 1024;
}
@Override
public long getTotalSlabMins() {
if (!USE_WATCHDOG) return -1;
long totalSlabMins = 0;
for (SlabStats slabStat : slabStats) {
totalSlabMins += slabStat.min;
}
return totalSlabMins;
}
@Override
public long getTotalEvicted() {
if (!USE_WATCHDOG) return -1;
long totalEvicted = 0;
for (SlabStats slabStat : slabStats) {
totalEvicted += slabStat.evictedTotal;
}
return totalEvicted;
}
public Map getUnrecycledBufs() {
return new HashMap<>(allocateRegistry);
}
@Override
public List queryUnrecycledBufs(int limit) {
if (limit < 1) throw new IllegalArgumentException("Limit must be >= 1");
Map danglingBufs = getUnrecycledBufs();
return danglingBufs.values().stream().sorted(comparingLong(Entry::getTimestamp)).limit(limit).collect(toList());
}
@Override
public List getPoolSlabs() {
List result = new ArrayList<>(slabs.length + 1);
String header = "SlotSize,Created,Reused,InPool,Total(Kb)";
if (USE_WATCHDOG) header += ",Min,EstMin,Error,Evicted";
result.add(header);
for (int i = 0; i < slabs.length; i++) {
int idx = (i + 32) % slabs.length;
long slabSize = idx == 32 ? 0 : 1L << idx;
ObjectPool slab = slabs[idx];
int count = slab.size();
String slabInfo =
slabSize + "," +
(STATS ? created[idx] : "-") + "," +
(STATS ? reused[idx] : "-") + "," +
count + "," +
slabSize * count / 1024;
if (USE_WATCHDOG) {
SlabStats slabStat = slabStats[idx];
slabInfo +=
"," + slabStat.min + "," +
String.format("%.1f", slabStat.estimatedMin) + "," +
String.format("%.1f", slabStat.estimatedError) + "," +
slabStat.evictedTotal;
}
result.add(slabInfo);
}
return result;
}
@Override
public void clear() {
ByteBufPool.clear();
}
@Override
public void clearRegistry() {
allocateRegistry.clear();
recycleRegistry.clear();
}
}
// region watchdog
public static final class SlabStats {
volatile int min = 0;
double estimatedMin;
int evictedTotal;
int evictedLast;
int evictedMax;
double estimatedError;
void clear() {
estimatedMin = estimatedError = evictedTotal = evictedLast = evictedMax = 0;
min = 0;
}
@Override
public String toString() {
return
"SlabStats{" +
"estimatedMin=" + estimatedMin +
", estimatedError=" + estimatedError +
", evictedTotal=" + evictedTotal +
", evictedLast=" + evictedLast +
", evictedMax=" + evictedMax +
'}';
}
}
private static void updateStats() {
for (int i = 0; i < slabs.length; i++) {
SlabStats stats = slabStats[i];
ObjectPool slab = slabs[i];
int min = stats.min;
stats.min = slab.size();
double error = Math.abs(stats.estimatedMin - min);
stats.estimatedError += (error - stats.estimatedError) * SMOOTHING_COEFF;
if (min < stats.estimatedMin) {
stats.estimatedMin = min;
} else {
stats.estimatedMin += (min - stats.estimatedMin) * SMOOTHING_COEFF;
}
}
}
private static void evict() {
for (int i = 0; i < slabs.length; i++) {
ObjectPool slab = slabs[i];
SlabStats stats = slabStats[i];
int evictCount = (int) Math.round(stats.estimatedMin - stats.estimatedError * WATCHDOG_ERROR_MARGIN);
stats.evictedLast = 0;
for (int j = 0; j < evictCount; j++) {
ByteBuf buf = slab.poll();
if (buf == null) {
if (USE_WATCHDOG) stats.min = 0;
break;
}
if (USE_WATCHDOG) {
int slabSize = slab.size();
//noinspection NonAtomicOperationOnVolatileField
stats.min = Math.min(stats.min, slabSize);
}
stats.estimatedMin--;
stats.evictedLast++;
if (REGISTRY) recycleRegistry.remove(buf);
}
stats.evictedTotal += stats.evictedLast;
stats.evictedMax = Math.max(stats.evictedLast, stats.evictedMax);
}
}
//endregion
}