package com.bigdata.io;
import java.nio.ByteBuffer;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.log4j.Logger;
import com.bigdata.counters.CAT;
import com.bigdata.counters.CounterSet;
import com.bigdata.counters.OneShotInstrument;
import com.bigdata.journal.IBufferStrategy;
import com.bigdata.journal.TemporaryRawStore;
import com.bigdata.journal.TransientBufferStrategy;
import com.bigdata.util.Bytes;
/**
* An instance of this class manages a JVM-wide pool of direct (aka native)
* {@link ByteBuffer}s. Methods are provided to acquire a {@link ByteBuffer}
* from the pool and to release a {@link ByteBuffer} back to the pool.
* <p>
* Note: There is a bug in the release of large temporary direct
* {@link ByteBuffer}s which motivates this class. For regular journals that
* overflow, the write cache is allocated once and handed off from journal to
* journal. However, there is no such opportunity for temporary stores.
* Unfortunately it is NOT an option to simply disable the write cache for
* temporary stores since NIO will allocate (and fail to release) an "temporary"
* direct buffer for the operation which transfers the data from the
* {@link TransientBufferStrategy} to disk. Therefore the data is copied into a
* temporary buffer allocated from this pool and then the buffer is either
* handed off to the {@link IBufferStrategy} for use as its write cache (in
* which case the {@link TemporaryRawStore} holds a reference to the buffer and
* releases it back to those pool when it is finalized) or the buffer is
* immediately released back to this pool.
* <p>
* Note: Precisely because of the bug which motivates this class, we DO NOT
* release buffers back to the JVM. This means that the size of a
* {@link DirectBufferPool} can only increase, but at least you get to (re-)use
* the memory that you have allocated rather than leaking it to the native heap.
*
* @see http://bugs.sun.com/bugdatabase/view_bug.do;jsessionid=8f
* ab76d1d4479fffffffffa5abfb09c719a30?bug_id=6210541
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*
* @todo It should be possible to define a method which attempts to release
* direct buffers back to the JVM. The JVM can eventually GC them after a
* full GC, but often not in time to avoid an OOM error on the Java heap.
*/
public class DirectBufferPool {
private static final Logger log = Logger
.getLogger(DirectBufferPool.class);
/**
* Object tracking state for allocated buffer instances. This is used to
* reject double-release of a buffer back to the pool, which is critical.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan
* Thompson</a>
*/
private class BufferState implements IBufferAccess {
/**
* The buffer instance. This is guarded by the monitor of the buffer
* state object (changes to this field are made while holding the
* monitor of the {@link BufferState} object). However, the field is
* marked as <code>volatile</code> so we can peek at it without holding
* the monitor's lock, e.g., in {@link #toString()}
*/
private volatile ByteBuffer buf;
/**
* The stack trace where the {@link ByteBuffer} was acquired IFF DEBUG
* and otherwise <code>null</code>.
*/
private final Throwable allocationStack;
/**
* The stack trace where the {@link ByteBuffer} was released IFF DEBUG
* and otherwise <code>null</code>. This is guarded by the monitor of
* the {@link BufferState} object.
*/
private Throwable releaseStack;
/**
* This is set to <code>true</code> iff the buffer is released by
* {@link #finalize()}. In this case, we do not treat an invocation
* of {@link #release(long, TimeUnit)} <i>after</i> the finalizer has
* run as a double-release. (Yes, this situation can arise...).
*/
private boolean releasedByFinalizer = false;
BufferState(final ByteBuffer buf) {
if (buf == null)
throw new IllegalArgumentException();
this.buf = buf;
this.allocationStack = (DEBUG ? new RuntimeException("Allocation")
: null);
}
/**
* The hash code depends only on the object id (NOT the buffer's data).
* <p>
* Note: {@link ByteBuffer#hashCode()} is a very heavy operator whose
* result depends on the data actually in the buffer at the time the
* operation is evaluated!
*/
public int hashCode() {
return super.hashCode();
}
/**
* Equality depends only on a reference checks.
* <p>
* Note: {@link ByteBuffer#equals(Object)} is very heavy operator whose
* result depends on the data actually in the buffer at the time the
* operation is evaluated!
*/
public boolean equals(final Object o) {
if (this == o) {
// Same BufferState, must be the same buffer.
return true;
}
if (!(o instanceof BufferState)) {
return false;
}
if (this.buf == ((BufferState) o).buf) {
/*
* We have two distinct BufferState references for the same
* ByteBuffer reference. This is an error. There should be a
* one-to-one correspondence.
*/
throw new AssertionError();
}
return false;
}
public String toString() {
final ByteBuffer tmp = this.buf;
return super.toString() + "{buf"
+ (tmp == null ? "N/A" : "buf.capacity=" + buf.capacity())
+ "}";
}
// Implement IDirectBuffer methods
public ByteBuffer buffer() {
synchronized (this) {
if (buf == null)
throw new IllegalStateException();
return buf;
}
}
public void release() throws InterruptedException {
release(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
}
public void release(final long timeout, final TimeUnit units)
throws InterruptedException {
/*
* Note: There is a data race between finalizers whose call graphs
* wind up requesting the release of the buffer. This occurs when a
* buffer user, such as a Journal, is being finalized. At that time,
* the IBufferAccess object will also be finalizable. Java does not
* define the ordering of those finalizer invocations so either the
* Journal may release() the IBufferState explicitly first or the
* IBufferState#finalized() method may run first. In either case we
* go through a synchronized(this) block, return immediately if the
* [buf] reference has already been cleared and otherwise return the
* buffer to the pool and clear the [buf] reference to null.
*/
synchronized (this) {
if (buf == null) {
if(releasedByFinalizer) {
/*
* This situation can arise. Just return quietly.
*/
return;
}
if (DEBUG) {
log.error("Double release: AllocationTrace",
allocationStack);
if (releaseStack == null)
log
.error("Double release: FirstReleaseStack NOT available");
else
log.error("Double release: FirstReleaseStack: "
+ releaseStack, releaseStack);
log.error("Double release: DoubleReleaseStack",
new RuntimeException("DoubleReleaseStack"));
}
return;
}
DirectBufferPool.this.release(buf, timeout, units);
buf = null;
if (DEBUG) {
/*
* The stack frame where the ByteBuffer was released.
*/
releaseStack = new RuntimeException("ReleaseTrace");
}
} // synchronized(this)
}// release(timeout,unit)
/*
* Note: It is apparent that the JVM can order things such that the
* finalize() method can be called before an invocation of release() on
* the BufferState object. Presumably this arises when a set of
* references are all due to be finalized because none of them are more
* than weakly reachable from a GC root. At that point, the JVM is faced
* with the (impossible) task of ordering their finalizer() invocations.
* Since object references are (in general) an undirected graph, it
* seems that Java will invoke the finalizers on those references in
* some undefined (and perhaps not definable) order. This can lead to a
* "double-release" situation where the first release was the JVM
* invoking the finalizer and the second release was a different
* finalizer invoking release() on this BufferState object.
*
* Given this state of affairs, the "right" thing to do is write the
* finalizer defensively for a concurrent environment. It should
* atomically release the buffer back to the pool and clear the buffer
* reference. We should then ignore the double-release request rather
* than throwing out an IllegalStateException.
*
* This appears to be the right thing to do if the application holds a
* hard reference to the BufferState object until it has release()ed the
* buffer. If the application fails to hold that hard reference, then
* putting the ByteBuffer back on the pool will cause concurrent data
* modification problems within the ByteBuffer. Applications MUST verify
* that they correctly hold that hard reference!
*/
protected void finalize() throws Throwable {
/*
* Ultra paranoid block designed to ensure that we do not double
* release the ByteBuffer to the owning pool via the action of
* another finalized.
*/
final ByteBuffer buf;
final int nacquired;
synchronized(this) {
buf = this.buf;
this.buf = null; // NB: Ignore FindBugs warning on this line!!!
nacquired = DirectBufferPool.this.acquired;
if (buf != null) {
releasedByFinalizer = true;
if (releaseStack == null) {
releaseStack = new RuntimeException(
"ReleasedInFinalizer");
}
}
}
if (buf == null)
return;
if (DEBUG) {
/*
* Note: This code path WILL NOT return the buffer to the pool.
* This is deliberate. When DEBUG is true we do not permit a
* buffer which was not correctly release to be reused.
*
* Note: A common cause of this is that the caller is holding
* onto the acquired ByteBuffer object rather than the
* IBufferAccess object. This permits the IBufferAccess
* reference to be finalized. When the IBufferAccess object is
* finalized, it will attempt to release the buffer (except in
* DEBUG mode). However, if the caller is holding onto the
* ByteBuffer then this is an error which can rapidly lead to
* corrupt data through concurrent modification (what happens is
* that the ByteBuffer is handed out to another thread in
* response to another acquire() and we now have two threads
* using the same ByteBuffer, each of which believes that they
* "own" the reference).
*/
leaked.increment();
final long nleaked = leaked.get();
log.error("Buffer release on finalize (nacquired=" + nacquired
+ ",nleaked=" + nleaked + "): AllocationStack",
allocationStack);
} else {
// log.error("Buffer release on finalize."); // NB: NOT an error.
/*
* TODO We do not currently set this.buf = buf if we are
* interrupted in release(buf) here, so this is not acid. But
* maybe we should accept the memory leak on that code path?
*/
DirectBufferPool.this.release(buf);
}
}
}
/**
* The name of the buffer pool.
*/
final private String name;
/**
* A pool of direct {@link ByteBuffer}s which may be acquired.
* <p>
* Note: This is NOT a weak reference collection since the JVM will leak
* native memory.
*/
final private BlockingQueue<ByteBuffer> pool;
/**
* The number {@link ByteBuffer}s allocated (must use {@link #lock} for
* updates or reads to be atomic). This counter is incremented each time a
* buffer is allocated. Since we do not free buffers when they are released
* (to prevent an effective JVM memory leak) this counter is never
* decremented.
*/
private int size = 0;
/**
* The #of {@link ByteBuffer}s which are currently acquired (must use
* {@link #lock} for updates or reads to be atomic). This counter is
* incremented when a buffer is acquired and decremented when a buffer
* is released.
*/
private int acquired = 0;
/**
* The #of buffers leaked out of {@link BufferState#finalize()} when
* {@link #DEBUG} is <code>true</code>.
*/
private final CAT leaked = new CAT();
/**
* The maximum #of {@link ByteBuffer}s that will be allocated.
*/
private final int poolCapacity;
/**
* The capacity of the {@link ByteBuffer}s managed by this pool.
*/
private final int bufferCapacity;
/**
* Lock used to serialize access to the other fields on this class.
*/
private final ReentrantLock lock = new ReentrantLock();
/**
* Condition used to await a buffer release.
*/
private final Condition bufferRelease = lock.newCondition();
/**
* Package private counter of the total #of acquired buffers in all pools.
* This is used to check for memory leaks in the test suites. The value is
* reset before/after each test.
*/
static final CAT totalAcquireCount = new CAT();
static final CAT totalReleaseCount = new CAT();
/**
* The name of this buffer pool instance.
*/
public String getName() {
return name;
}
/**
* The #of {@link ByteBuffer}s which are currently acquired. This counter is
* incremented when a buffer is acquired and decremented when a buffer is
* released.
*/
public int getAcquiredBufferCount() {
lock.lock();
try {
return acquired;
} finally {
lock.unlock();
}
}
/**
* The maximum capacity in buffers of the {@link DirectBufferPool} as
* specified to the constructor.
*/
public int getPoolCapacity() {
return poolCapacity;
}
/**
* The approximate #of {@link ByteBuffer}s currently managed by this
* pool.
*/
public int getPoolSize() {
lock.lock();
try {
return size;
} finally {
lock.unlock();
}
}
/**
* The capacity in bytes of the {@link ByteBuffer}s managed by this pool as
* specified to the constructor.
*/
public int getBufferCapacity() {
return bufferCapacity;
}
/**
* Options for provisioning the <em>static</em> instance of the
* {@link DirectBufferPool}.
* <p>
* Note: Since the {@link DirectBufferPool#INSTANCE} is static all of these
* options MUST be specified on the command line using <code>-D</code> to
* define the relevant property.
* <p>
* Note: The default configuration will never block but is not bounded in
* how many buffers it will allocate.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
public interface Options {
/**
* The capacity of the {@link DirectBufferPool} is the maximum #of
* direct {@link ByteBuffer} instances that may reside in the pool
* (default {@value #DEFAULT_POOL_CAPACITY}).
* <p>
* Note: Placing a limit on the pool size could cause threads to
* deadlock awaiting a direct buffer from the pool. For this reason is
* it good practice to use
* {@link DirectBufferPool#acquire(long, TimeUnit)} with a timeout.
*/
String POOL_CAPACITY = DirectBufferPool.class.getName()
+ ".poolCapacity";
/**
* The default pool capacity (no limit).
*/
String DEFAULT_POOL_CAPACITY = "" + Integer.MAX_VALUE;
/**
* The capacity in bytes of the direct {@link ByteBuffer} instances
* allocated and managed by the {@link DirectBufferPool} ({@link #DEFAULT_BUFFER_CAPACITY}).
*/
String BUFFER_CAPACITY = DirectBufferPool.class.getName()
+ ".bufferCapacity";
/**
* The default capacity of the allocated buffers.
*/
String DEFAULT_BUFFER_CAPACITY = "" + Bytes.megabyte32 * 1;
/**
* Option to use conservative assumptions about buffer release and to
* report allocation stack traces for undesired events (double-release,
* never released, etc).
*/
String DEBUG = DirectBufferPool.class.getName() + ".debug";
String DEFAULT_DEBUG = "false";
}
/**
* @see Options#DEBUG
*/
private final static boolean DEBUG;
/**
* A JVM-wide pool of direct {@link ByteBuffer}s used for a variety of
* purposes with a default {@link Options#BUFFER_CAPACITY} of
* <code>1 MB</code>.
* <p>
* Note: {@link #acquire()} requests will block once the pool capacity has
* been reached until a buffer is {@link #release(ByteBuffer)}ed.
*/
public final static DirectBufferPool INSTANCE;
// /**
// * A JVM-wide pool of direct {@link ByteBuffer}s with a default
// * {@link Options#BUFFER_CAPACITY} of <code>10 MB</code>. The main use case
// * for the 10M buffers are multi-block IOs for the {@link IndexSegment}s.
// */
// public final static DirectBufferPool INSTANCE_10M;
/**
* An unbounded list of all {@link DirectBufferPool} instances.
*/
static private List<DirectBufferPool> pools = Collections
.synchronizedList(new LinkedList<DirectBufferPool>());
static {
final int poolCapacity = Integer.parseInt(System.getProperty(
Options.POOL_CAPACITY, Options.DEFAULT_POOL_CAPACITY));
if(log.isInfoEnabled())
log.info(Options.POOL_CAPACITY + "=" + poolCapacity);
final int bufferCapacity = Integer.parseInt(System.getProperty(
Options.BUFFER_CAPACITY, Options.DEFAULT_BUFFER_CAPACITY));
if (log.isInfoEnabled())
log.info(Options.BUFFER_CAPACITY + "=" + bufferCapacity);
DEBUG = Boolean.valueOf(System.getProperty(Options.DEBUG,
Options.DEFAULT_DEBUG));
INSTANCE = new DirectBufferPool(//
"default",//
poolCapacity,//
bufferCapacity//
);
// INSTANCE_10M = new DirectBufferPool(//
// "10M",//
// Integer.MAX_VALUE, // poolCapacity
// 10 * Bytes.megabyte32 // bufferCapacity
// );
/*
* This configuration will block if there is a concurrent demand for
* more than [poolCapacity] buffers.
*
* This is a pretty reasonable configuration for deployment. It will
* serialize (or timeout) concurrent operations requiring more than
* [poolCapacity] buffers in aggregate demand and each buffer is
* modestly large so that the write cache will have good
* performance. The total native memory demand for temporary stores
* is capped at [poolCapacity * bufferCapacity] bytes, which is
* again a reasonable value.
*/
// 100, // poolCapacity
// 1 * Bytes.megabyte32 // bufferCapacity
/*
* This configuration may be useful for stress testing.
*/
// 1, // poolCapacity
// Bytes.kilobyte32
}
/**
* Create a direct {@link ByteBuffer} pool.
* <p>
* Note: When the <i>poolSize</i> is bounded then {@link #acquire()} MAY
* block. This can introduce deadlocks into the application. You can use a
* timeout to limit the sensitivity to deadlocks or you can use an unbounded
* pool and accept that {@link OutOfMemoryError}s will arise if there is
* too much concurrent demand for the buffers supplied by this pool.
*
* @param poolCapacity
* The maximum capacity of the pool. Use
* {@link Integer#MAX_VALUE} to have a pool with an unbounded
* number of buffers.
* @param bufferCapacity
* The capacity of the {@link ByteBuffer}s managed by this pool.
*
* @see #INSTANCE
*/
protected DirectBufferPool(final String name, final int poolCapacity,
final int bufferCapacity) {
if (name == null)
throw new IllegalArgumentException();
if (poolCapacity <= 0)
throw new IllegalArgumentException();
if (bufferCapacity <= 0)
throw new IllegalArgumentException();
this.name = name;
this.poolCapacity = poolCapacity;
this.bufferCapacity = bufferCapacity;
this.pool = new LinkedBlockingQueue<ByteBuffer>(poolCapacity);
pools.add(this);
}
/**
* Return an {@link IBufferAccess} wrapping a direct {@link ByteBuffer}. The
* capacity of the buffer is determined by the configuration of this pool.
* The position will be equal to zero, the limit will be equal to the
* capacity, and the mark will not be set.
* <p>
* Note: This method will block if there are no free buffers in the pool and
* the pool was configured with a maximum capacity. It WILL log an error if
* it blocks. While blocking is not very safe, using a heap (vs direct)
* {@link ByteBuffer} is not very safe either since Java NIO will allocate a
* temporary direct {@link ByteBuffer} for IOs and that can both run out of
* memory and leak memory.
*
* @return A direct {@link ByteBuffer}.
*
* @throws InterruptedException
* if the caller's {@link Thread} is interrupted awaiting a
* buffer.
* @throws OutOfMemoryError
* if there is not enough free memory to fulfill the request.
*/
public IBufferAccess acquire() throws InterruptedException {
try {
return acquire(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
} catch (TimeoutException e) {
// The TimeoutException should not be thrown.
throw new AssertionError(e);
}
}
/**
* Return an {@link IBufferAccess} wrapping a direct {@link ByteBuffer}. The
* capacity of the buffer is determined by the configuration of this pool.
* The position will be equal to zero, the limit will be equal to the
* capacity, and the mark will not be set.
* <p>
* Note: This method will block if there are no free buffers in the pool and
* the pool was configured with a maximum capacity. In addition it MAY block
* if there is not enough free memory to fulfill the request. It WILL log an
* error if it blocks. While blocking is not very safe, using a heap (vs
* direct) {@link ByteBuffer} is not very safe either since Java NIO will
* allocate a temporary direct {@link ByteBuffer} for IOs and that can both
* run out of memory and leak memory.
*
* @param timeout
* The timeout.
* @param unit
* The units for that timeout.
*
* @return A direct {@link ByteBuffer}.
*
* @throws InterruptedException
* if the caller's {@link Thread} is interrupted awaiting a
* buffer.
* @throws TimeoutException
*/
public IBufferAccess acquire(final long timeout, final TimeUnit unit)
throws InterruptedException, TimeoutException {
// if(log.isInfoEnabled())
// log.info("");
lock.lock();
try {
if (pool.isEmpty()) {
allocate(timeout, unit);
}
// the head of the pool must exist.
final ByteBuffer buf = pool.take();
acquired++;
totalAcquireCount.increment();
// limit -> capacity; pos-> 0; mark cleared.
buf.clear();
if (log.isTraceEnabled()) {
final Throwable t = new RuntimeException(
"Stack trace of buffer acquisition");
log.trace(t, t);
}
return new BufferState(buf);
} finally {
lock.unlock();
}
}
/**
* Release a direct {@link ByteBuffer} allocated by this pool back to the
* pool.
*
* @param b
* The buffer.
*
* @throws IllegalArgumentException
* if the buffer is <code>null</code>.
* @throws IllegalArgumentException
* if the buffer does not belong to this pool.
* @throws IllegalArgumentException
* if the buffer has already been released.
* @throws InterruptedException
*/
final private void release(final ByteBuffer b) throws InterruptedException {
if (!release(b, Long.MAX_VALUE, TimeUnit.MILLISECONDS)) {
throw new AssertionError();
}
}
/**
* Release a direct {@link ByteBuffer} allocated by this pool back to the
* pool.
*
* @param b
* The buffer.
*
* @throws IllegalArgumentException
* if the buffer is <code>null</code>.
* @throws IllegalArgumentException
* if the buffer does not belong to this pool.
* @throws IllegalArgumentException
* if the buffer has already been released.
* @throws InterruptedException
*/
final private boolean release(final ByteBuffer b, final long timeout,
final TimeUnit units) throws InterruptedException {
// if(log.isInfoEnabled())
// log.info("");
if (b == null)
throw new IllegalArgumentException();
lock.lock();
try {
// add to the pool.
if(!pool.offer(b, timeout, units))
return false;
acquired--;
totalReleaseCount.increment();
/*
* Signal ONE thread that there is a buffer available.
*
* Note: There is the potential for this signal to be missed if
* the thread waiting in [allocate] allows itself to be
* interrupted once the signal has arrived and before it has
* returned to the caller. Once the buffer is in the caller's
* hands it is up to the caller to ensure that it is released
* back to the pool, e.g., in finalize().
*
* Note: Another way to handle this is to signalAll() and then
* have the thread check to see if the pool is empty and restart
* its wait (after subtracting out the time already elapsed). This
* is doubtless more robust.
*/
bufferRelease.signal();
if (log.isTraceEnabled()) {
final Throwable t = new RuntimeException(
"Stack trace of buffer release");
log.trace(t, t);
}
return true;
} finally {
lock.unlock();
}
}
/**
* Attempts to allocate another direct {@link ByteBuffer}. If
* successful then it will add the buffer to the {@link #pool}.
*
* @throws InterruptedException
* @throws TimeoutException
*
* @throws
*/
private void allocate(long timeout, TimeUnit unit)
throws InterruptedException, TimeoutException {
assert lock.isHeldByCurrentThread();
if(log.isDebugEnabled())
log.debug("");
try {
if (size >= poolCapacity) {
/*
* Wait for a free buffer since the pool is at its capacity.
*/
log.error("Pool is at capacity - waiting for a free buffer");
awaitFreeBuffer(timeout, unit);
}
// allocate a buffer
final ByteBuffer b = ByteBuffer.allocateDirect(bufferCapacity);
// update the pool size.
size++;
// add to the pool.
pool.add(b);
/*
* There is now a buffer in the pool and the caller will get it
* since they hold the lock.
*/
return;
} catch (OutOfMemoryError err) {
/*
* Note: It is dangerous wait if the JVM is out of memory since this
* could deadlock even when there is an unlimited capacity on the
* pool. It is much safer to throw out an exception.
*/
// log.error("Not enough native memory - will await a free buffer: "
// + err, err);
//
// awaitFreeBuffer(timeout, unit);
throw err;
}
}
private void awaitFreeBuffer(long timeout, TimeUnit unit)
throws InterruptedException, TimeoutException {
// await a buffer to appear in the pool.
if (!bufferRelease.await(timeout, unit)) {
throw new TimeoutException();
}
/*
* There is now a buffer in the pool and the caller will get it
* since they hold the lock.
*
* Note: From here until the caller gets the buffer either (a)
* do NOT allow the current thread to be interrupted. Failure to
* adhere to this advice can result in a buffer remaining the
* pool but no thread awaiting that released buffer noticing it
* there!
*/
assert !pool.isEmpty();
return;
}
/**
* Return the {@link CounterSet} for the {@link DirectBufferPool}.
* <dl>
* <dt>poolSize</dt>
* <dd>The approximate number of direct {@link ByteBuffer}s currently
* managed by the pool.</dd>
* <dt>poolCapacity</dt>
* <dd>The maximum number of direct {@link ByteBuffer}s that may be
* allocated by the pool.</dd>
* <dt>bufferCapacity</dt>
* <dd>The capacity in bytes of each direct {@link ByteBuffer} associated
* with a given pool.</dd>
* <dt>acquired</dt>
* <dd>The number of direct {@link ByteBuffer}s currently acquired by the
* application.</dd>
* <dt>bytesUsed</dt>
* <dd>The number of bytes managed by the pool.</dd>
* </dl>
*
* @return The counters.
*/
static public CounterSet getCounters() {
final CounterSet tmp = new CounterSet();
// #of buffer pools.
int bufferPoolCount = 0;
// #of buffers currently allocated across all buffer pools.
int bufferInUseCount = 0;
// #of buffers currently acquired across all buffer pools.
int totalAcquired = 0;
// #of bytes currently allocated across all buffer pools.
final AtomicLong totalBytesUsed = new AtomicLong(0L);
// For each buffer pool.
for (DirectBufferPool p : pools) {
final CounterSet c = tmp.makePath(p.getName());
final int poolSize = p.getPoolSize();
final int poolCapacity = p.getPoolCapacity();
final int bufferCapacity = p.getBufferCapacity();
final int acquired = p.getAcquiredBufferCount();
final long nleaked = p.leaked.get();
final long bytesUsed = poolSize * bufferCapacity;
bufferPoolCount++;
bufferInUseCount += poolSize;
totalAcquired += acquired;
totalBytesUsed.addAndGet(bytesUsed);
c.addCounter("poolCapacity", new OneShotInstrument<Integer>(
poolCapacity));
c.addCounter("bufferCapacity", new OneShotInstrument<Integer>(
bufferCapacity));
c.addCounter("acquired", new OneShotInstrument<Integer>(acquired));
c.addCounter("leaked", new OneShotInstrument<Long>(nleaked));
c.addCounter("poolSize", new OneShotInstrument<Integer>(poolSize));
/*
* #of bytes allocated and held by the DirectBufferPool.
*/
c.addCounter("bytesUsed", new OneShotInstrument<Long>(bytesUsed));
} // next DirectBufferPool
/*
* Totals.
*/
tmp.addCounter("totalAcquired", new OneShotInstrument<Integer>(
totalAcquired));
tmp.addCounter("bufferPoolCount", new OneShotInstrument<Integer>(
bufferPoolCount));
tmp.addCounter("bufferInUseCount", new OneShotInstrument<Integer>(
bufferInUseCount));
tmp.addCounter("totalBytesUsed", new OneShotInstrument<Long>(
totalBytesUsed.get()));
return tmp;
}
}