org.apache.druid.frame.allocation

Class ArenaMemoryAllocator

java.lang.Object

org.apache.druid.frame.allocation.ArenaMemoryAllocator

All Implemented Interfaces:

MemoryAllocator

public class ArenaMemoryAllocator
extends Object
implements MemoryAllocator

Allocator that uses a reusable WritableMemory arena. The allocator maintains a high watermark that is reset to zero when all outstanding allocations have been freed.

Method Summary

Modifier and Type	Method and Description
Optional<ResourceHolder<org.apache.datasketches.memory.WritableMemory>>	allocate(long size) Allocates a block of memory of capacity .
long	available() Returns the number of bytes available for allocations.
long	capacity() Returns the number of bytes managed by this allocator.
static ArenaMemoryAllocator	create(ByteBuffer buffer) Creates an allocator based on a specific ByteBuffer.
static ArenaMemoryAllocator	createOnHeap(int capacity) Creates an allocator of a specific size using an on-heap ByteBuffer.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

create

public static ArenaMemoryAllocator create(ByteBuffer buffer)

Creates an allocator based on a specific ByteBuffer. The buffer is never freed, so to ensure proper cleanup when the allocator is discarded, this buffer must be on-heap (so it can be garbage collected) rather than off-heap.

createOnHeap

public static ArenaMemoryAllocator createOnHeap(int capacity)

Creates an allocator of a specific size using an on-heap ByteBuffer.

allocate

public Optional<ResourceHolder<org.apache.datasketches.memory.WritableMemory>> allocate(long size)

Description copied from interface: MemoryAllocator

Allocates a block of memory of capacity . Returns empty if no more memory is available. The memory can be freed by closing the returned ResourceHolder. The returned WritableMemory object will use little-endian byte order.

Specified by:

allocate in interface MemoryAllocator

available

public long available()

Description copied from interface: MemoryAllocator

Returns the number of bytes available for allocations. May return Long.MAX_VALUE if there is no inherent limit. This generally does not mean you can actually allocate 9 exabytes.

Specified by:

available in interface MemoryAllocator

capacity

public long capacity()

Description copied from interface: MemoryAllocator

Returns the number of bytes managed by this allocator. When no memory has been allocated yet, this is identical to MemoryAllocator.available(). May return Long.MAX_VALUE if there is no inherent limit. This generally does not mean you can actually allocate 9 exabytes.

Specified by:

capacity in interface MemoryAllocator