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Ensure WeakOrderQueue can be collected fast enough #5569

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Ensure WeakOrderQueue can be collected fast enough #5569

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53 changes: 29 additions & 24 deletions common/src/main/java/io/netty/util/Recycler.java
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Expand Up @@ -223,7 +223,7 @@ private static final class Link extends AtomicInteger {
private WeakOrderQueue next;
private final WeakReference<Thread> owner;
private final int id = ID_GENERATOR.getAndIncrement();
private final Stack<?> stack;
private final AtomicInteger availableSharedCapacity;

WeakOrderQueue(Stack<?> stack, Thread thread) {
head = tail = new Link();
Expand All @@ -232,19 +232,42 @@ private static final class Link extends AtomicInteger {
next = stack.head;
stack.head = this;
}
this.stack = stack;

// Its important that we not store the Stack itself in the WeakOrderQueue as the Stack also is used in
// the WeakHashMap as key. So just store the enclosed AtomicInteger which should allow to have the
// Stack itself GCed.
availableSharedCapacity = stack.availableSharedCapacity;
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the stack doesn't actually use this variable ... should we move it outside the stack and lazy create it here in the WeakOrderQueue?

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@Scottmitch nope as it needs to be shared across all WeakOrderQueueinstances that belong to a Stack.

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+1 makes sense


// We allocated a Link so reserve the space
boolean reserved = stack.reserveSpace(LINK_CAPACITY);
boolean reserved = reserveSpace(LINK_CAPACITY);
assert reserved;
}

private boolean reserveSpace(int space) {
assert space >= 0;
for (;;) {
int available = availableSharedCapacity.get();
if (available < space) {
return false;
}
if (availableSharedCapacity.compareAndSet(available, available - space)) {
return true;
}
}
}

private void reclaimSpace(int space) {
assert space >= 0;
availableSharedCapacity.addAndGet(space);
}

void add(DefaultHandle<?> handle) {
handle.lastRecycledId = id;

Link tail = this.tail;
int writeIndex;
if ((writeIndex = tail.get()) == LINK_CAPACITY) {
if (!stack.reserveSpace(LINK_CAPACITY)) {
if (!reserveSpace(LINK_CAPACITY)) {
// Drop it.
return;
}
Expand Down Expand Up @@ -314,7 +337,7 @@ boolean transfer(Stack<?> dst) {

if (srcEnd == LINK_CAPACITY && head.next != null) {
// Add capacity back as the Link is GCed.
stack.reclaimSpace(LINK_CAPACITY);
reclaimSpace(LINK_CAPACITY);

this.head = head.next;
}
Expand All @@ -339,7 +362,7 @@ static final class Stack<T> {
private DefaultHandle<?>[] elements;
private final int maxCapacity;
private int size;
private final AtomicInteger availableSharedCapacity;
final AtomicInteger availableSharedCapacity;

private volatile WeakOrderQueue head;
private WeakOrderQueue cursor, prev;
Expand All @@ -352,24 +375,6 @@ static final class Stack<T> {
elements = new DefaultHandle[min(INITIAL_CAPACITY, maxCapacity)];
}

boolean reserveSpace(int space) {
assert space >= 0;
for (;;) {
int available = availableSharedCapacity.get();
if (available < space) {
return false;
}
if (availableSharedCapacity.compareAndSet(available, available - space)) {
return true;
}
}
}

void reclaimSpace(int space) {
assert space >= 0;
availableSharedCapacity.addAndGet(space);
}

int increaseCapacity(int expectedCapacity) {
int newCapacity = elements.length;
int maxCapacity = this.maxCapacity;
Expand Down