com.yahoo.memory

Class AllocMemory

java.lang.Object

com.yahoo.memory.NativeMemory

com.yahoo.memory.AllocMemory

All Implemented Interfaces:

Memory

public class AllocMemory
extends NativeMemory

The AllocMemory class is a subclass of NativeMemory¹. AllocMemory is used to allocate direct, off-heap memory, which can then be accessed by the NativeMemory methods.

This class leverages the JVM Cleaner class that replaces Object.finalize() and serves as a back-up if the calling class does not call freeMemory().

Author:

Lee Rhodes

Constructor Summary

Constructors

Constructor and Description
AllocMemory(long capacityBytes) Constructor to allocate native memory.
AllocMemory(long capacityBytes, MemoryRequest memReq) Constructor for allocate native memory with MemoryRequest.
AllocMemory(NativeMemory origMem, long copyToBytes, long capacityBytes, boolean clear, MemoryRequest memReq) Constructor to allocate new off-heap NativeMemory, copy from the given origMem, and optionally clear the remainder.
AllocMemory(NativeMemory origMem, long newCapacityBytes, MemoryRequest memReq) Constructor to allocate new off-heap native memory, copy the contents from the given origMem.

Method Summary

Modifier and Type	Method and Description
void	freeMemory() Because the Memory classes now use the JVM Cleaner, calling freeMemory(), which also calls Cleaner, is optional.

Methods inherited from class com.yahoo.memory.NativeMemory

addAndGetInt, addAndGetLong, array, asReadOnlyMemory, byteBuffer, clear, clear, clearBits, compareAndSwapInt, compareAndSwapLong, copy, copy, copy, fill, fill, getAddress, getAndSetInt, getAndSetLong, getBoolean, getBooleanArray, getByte, getByteArray, getCapacity, getChar, getCharArray, getCumulativeOffset, getDouble, getDoubleArray, getFloat, getFloatArray, getInt, getIntArray, getLong, getLongArray, getMemoryRequest, getParent, getShort, getShortArray, hasArray, hasByteBuffer, isAllBitsClear, isAllBitsSet, isAllocated, isAnyBitsClear, isAnyBitsSet, isDirect, isReadOnly, putBoolean, putBooleanArray, putByte, putByteArray, putChar, putCharArray, putDouble, putDoubleArray, putFloat, putFloatArray, putInt, putIntArray, putLong, putLongArray, putShort, putShortArray, setBits, setMemoryRequest, toHexString, wrap

Methods inherited from class java.lang.Object

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

Constructor Detail

AllocMemory

public AllocMemory(long capacityBytes)

Constructor to allocate native memory.

Allocates and provides access to capacityBytes directly in native (off-heap) memory leveraging the Memory interface. The MemoryRequest callback is set to null. The allocated memory will be 8-byte aligned, but may not be page aligned.

Parameters:

capacityBytes - the size in bytes of the native memory

AllocMemory

public AllocMemory(long capacityBytes,
                   MemoryRequest memReq)

Constructor for allocate native memory with MemoryRequest.

Allocates and provides access to capacityBytes directly in native (off-heap) memory leveraging the Memory interface. The allocated memory will be 8-byte aligned, but may not be page aligned.

Parameters:

capacityBytes - the size in bytes of the native memory

memReq - The MemoryRequest callback

AllocMemory

public AllocMemory(NativeMemory origMem,
                   long newCapacityBytes,
                   MemoryRequest memReq)

Constructor to allocate new off-heap native memory, copy the contents from the given origMem.

Reallocates the given off-heap NativeMemory to a new a new native (off-heap) memory location and copies the contents of the original given NativeMemory to the new location. Any memory beyond the capacity of the original given NativeMemory will be uninitialized. The new allocated memory will be 8-byte aligned, but may not be page aligned.

Parameters:

origMem - The original NativeMemory that needs its contents to be reallocated. It must not be null.

newCapacityBytes - the desired new capacity of the newly allocated memory in bytes

memReq - The MemoryRequest callback, which may be null.

AllocMemory

public AllocMemory(NativeMemory origMem,
                   long copyToBytes,
                   long capacityBytes,
                   boolean clear,
                   MemoryRequest memReq)

Constructor to allocate new off-heap NativeMemory, copy from the given origMem, and optionally clear the remainder.

Allocate a new native (off-heap) memory with capacityBytes; copy the contents of origMem from zero to copyToBytes; clear the new memory from copyToBytes to capacityBytes. The new allocated memory will be 8-byte aligned, but may not be page aligned.

Parameters:

origMem - The original Memory, a portion of which will be copied to the newly allocated NativeMemory. The reference must not be null. This origMem is not modified in any way, and may be reused .

copyToBytes - the upper limit of the region to be copied from origMem to the newly allocated memory, and the lower limit of the region to be cleared, if requested.

capacityBytes - the desired new capacity of the newly allocated memory in bytes and the upper limit of the region to be cleared.

clear - if true the remaining region from copyToBytes to capacityBytes will be cleared.

memReq - The MemoryRequest callback, which may be null.

Method Detail

freeMemory

public void freeMemory()

Description copied from interface: Memory

Because the Memory classes now use the JVM Cleaner, calling freeMemory(), which also calls Cleaner, is optional. In any case, calling freeMemory() is only relevant for Memory objects that have actually allocated native memory, which are those that have been allocated using AllocMemory or MemoryMappedFile.

Preemptively calling freeMemory() may reduce the load on the JVM GarbageCollector, but the significance of this will have to be verified in the target system environment. Calling freeMemory() always disables the current instance by setting the capacity to zero.

Specified by:

freeMemory in interface Memory

Overrides:

freeMemory in class NativeMemory