序
本文主要研究一下flink的MemoryPool
MemoryPool
flink-runtime_2.11-1.7.2-sources.jar!/org/apache/flink/runtime/memory/MemoryManager.java
abstract static class MemoryPool {
abstract int getNumberOfAvailableMemorySegments();
abstract MemorySegment allocateNewSegment(Object owner);
abstract MemorySegment requestSegmentFromPool(Object owner);
abstract void returnSegmentToPool(MemorySegment segment);
abstract void clear();
}
- MemoryPool定义了getNumberOfAvailableMemorySegments、allocateNewSegment、requestSegmentFromPool、returnSegmentToPool、clear这几个抽象方法；它有HybridHeapMemoryPool、HybridOffHeapMemoryPool这两个子类
HybridHeapMemoryPool
flink-runtime_2.11-1.7.2-sources.jar!/org/apache/flink/runtime/memory/MemoryManager.java
static final class HybridHeapMemoryPool extends MemoryPool {
/** The collection of available memory segments. */
private final ArrayDeque availableMemory;
private final int segmentSize;
HybridHeapMemoryPool(int numInitialSegments, int segmentSize) {
this.availableMemory = new ArrayDeque<>(numInitialSegments);
this.segmentSize = segmentSize;
for (int i = 0; i < numInitialSegments; i++) {
this.availableMemory.add(new byte[segmentSize]);
}
}
@Override
MemorySegment allocateNewSegment(Object owner) {
return MemorySegmentFactory.allocateUnpooledSegment(segmentSize, owner);
}
@Override
MemorySegment requestSegmentFromPool(Object owner) {
byte[] buf = availableMemory.remove();
return MemorySegmentFactory.wrapPooledHeapMemory(buf, owner);
}
@Override
void returnSegmentToPool(MemorySegment segment) {
if (segment.getClass() == HybridMemorySegment.class) {
HybridMemorySegment heapSegment = (HybridMemorySegment) segment;
availableMemory.add(heapSegment.getArray());
heapSegment.free();
}
else {
throw new IllegalArgumentException("Memory segment is not a " + HybridMemorySegment.class.getSimpleName());
}
}
@Override
protected int getNumberOfAvailableMemorySegments() {
return availableMemory.size();
}
@Override
void clear() {
availableMemory.clear();
}
}
- HybridHeapMemoryPool继承了MemoryPool，它使用的是jvm的heap内存；构造器接收numInitialSegments、segmentSize两个参数用于初始化availableMemory这个ArrayDeque，该queue的元素类型为byte[]
- allocateNewSegment方法调用的是MemorySegmentFactory.allocateUnpooledSegment，用于分配unpooled memory；requestSegmentFromPool方法调用的是availableMemory.remove()，然后调用MemorySegmentFactory.wrapPooledHeapMemory包装为MemorySegment，这个方法没有判断ArrayDeque的大小就直接remove，需要注意
- returnSegmentToPool方法只对HybridMemorySegment类型进行处理，首先将它的byte[]归还到availableMemory，之后调用heapSegment.free()释放；getNumberOfAvailableMemorySegments方法返回的是availableMemory.size()；clear方法调用的是availableMemory.clear()
HybridOffHeapMemoryPool
flink-runtime_2.11-1.7.2-sources.jar!/org/apache/flink/runtime/memory/MemoryManager.java
static final class HybridOffHeapMemoryPool extends MemoryPool {
/** The collection of available memory segments. */
private final ArrayDeque availableMemory;
private final int segmentSize;
HybridOffHeapMemoryPool(int numInitialSegments, int segmentSize) {
this.availableMemory = new ArrayDeque<>(numInitialSegments);
this.segmentSize = segmentSize;
for (int i = 0; i < numInitialSegments; i++) {
this.availableMemory.add(ByteBuffer.allocateDirect(segmentSize));
}
}
@Override
MemorySegment allocateNewSegment(Object owner) {
return MemorySegmentFactory.allocateUnpooledOffHeapMemory(segmentSize, owner);
}
@Override
MemorySegment requestSegmentFromPool(Object owner) {
ByteBuffer buf = availableMemory.remove();
return MemorySegmentFactory.wrapPooledOffHeapMemory(buf, owner);
}
@Override
void returnSegmentToPool(MemorySegment segment) {
if (segment.getClass() == HybridMemorySegment.class) {
HybridMemorySegment hybridSegment = (HybridMemorySegment) segment;
ByteBuffer buf = hybridSegment.getOffHeapBuffer();
availableMemory.add(buf);
hybridSegment.free();
}
else {
throw new IllegalArgumentException("Memory segment is not a " + HybridMemorySegment.class.getSimpleName());
}
}
@Override
protected int getNumberOfAvailableMemorySegments() {
return availableMemory.size();
}
@Override
void clear() {
availableMemory.clear();
}
}
- HybridOffHeapMemoryPool继承了MemoryPool，它使用的是OffHeap；构造器接收numInitialSegments、segmentSize两个参数用于初始化availableMemory这个ArrayDeque，该queue的元素类型为ByteBuffer
- allocateNewSegment方法调用的是MemorySegmentFactory.allocateUnpooledOffHeapMemory，用于分配unpooled off-heap memory；requestSegmentFromPool方法调用的是availableMemory.remove()，然后调用MemorySegmentFactory.wrapPooledOffHeapMemory包装为MemorySegment，这个方法没有判断ArrayDeque的大小就直接remove，需要注意
- returnSegmentToPool方法只对HybridMemorySegment类型进行处理，首先将它的ByteBuffer归还到availableMemory，之后调用heapSegment.free()释放；getNumberOfAvailableMemorySegments方法返回的是availableMemory.size()；clear方法调用的是availableMemory.clear()
小结
- MemoryPool定义了getNumberOfAvailableMemorySegments、allocateNewSegment、requestSegmentFromPool、returnSegmentToPool、clear这几个抽象方法；它有HybridHeapMemoryPool、HybridOffHeapMemoryPool这两个子类
- HybridHeapMemoryPool继承了MemoryPool，它使用的是jvm的heap内存；构造器接收numInitialSegments、segmentSize两个参数用于初始化availableMemory这个ArrayDeque，该queue的元素类型为byte[]；allocateNewSegment方法调用的是MemorySegmentFactory.allocateUnpooledSegment，用于分配unpooled memory；requestSegmentFromPool方法调用的是availableMemory.remove()，然后调用MemorySegmentFactory.wrapPooledHeapMemory包装为MemorySegment，这个方法没有判断ArrayDeque的大小就直接remove，需要注意；returnSegmentToPool方法只对HybridMemorySegment类型进行处理，首先将它的byte[]归还到availableMemory，之后调用heapSegment.free()释放；getNumberOfAvailableMemorySegments方法返回的是availableMemory.size()；clear方法调用的是availableMemory.clear()
- HybridOffHeapMemoryPool继承了MemoryPool，它使用的是OffHeap；构造器接收numInitialSegments、segmentSize两个参数用于初始化availableMemory这个ArrayDeque，该queue的元素类型为ByteBuffer；allocateNewSegment方法调用的是MemorySegmentFactory.allocateUnpooledOffHeapMemory，用于分配unpooled off-heap memory；requestSegmentFromPool方法调用的是availableMemory.remove()，然后调用MemorySegmentFactory.wrapPooledOffHeapMemory包装为MemorySegment，这个方法没有判断ArrayDeque的大小就直接remove，需要注意；returnSegmentToPool方法只对HybridMemorySegment类型进行处理，首先将它的ByteBuffer归还到availableMemory，之后调用heapSegment.free()释放；getNumberOfAvailableMemorySegments方法返回的是availableMemory.size()；clear方法调用的是availableMemory.clear()
doc
- MemoryManager