为什么80%的码农都做不了架构师?>>>
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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<byte[]> 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]);}}@OverrideMemorySegment allocateNewSegment(Object owner) {return MemorySegmentFactory.allocateUnpooledSegment(segmentSize, owner);}@OverrideMemorySegment requestSegmentFromPool(Object owner) {byte[] buf = availableMemory.remove();return MemorySegmentFactory.wrapPooledHeapMemory(buf, owner);}@Overridevoid 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());}}@Overrideprotected int getNumberOfAvailableMemorySegments() {return availableMemory.size();}@Overridevoid 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<ByteBuffer> 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));}}@OverrideMemorySegment allocateNewSegment(Object owner) {return MemorySegmentFactory.allocateUnpooledOffHeapMemory(segmentSize, owner);}@OverrideMemorySegment requestSegmentFromPool(Object owner) {ByteBuffer buf = availableMemory.remove();return MemorySegmentFactory.wrapPooledOffHeapMemory(buf, owner);}@Overridevoid 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());}}@Overrideprotected int getNumberOfAvailableMemorySegments() {return availableMemory.size();}@Overridevoid 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