Package com.metsci.glimpse.util.buffer

Class DirectBufferDealloc

java.lang.Object

com.metsci.glimpse.util.buffer.DirectBufferDealloc

public class DirectBufferDealloc
extends Object

Uses non-public APIs (e.g. via reflection) to free the off-heap memory that backs an NIO direct buffer. Normally such off-heap memory is not freed until the garbage collector finalizes the direct buffer. This delay causes problems when a lot of off-heap memory is used, but garbage collections are infrequent.

Works on Oracle/OpenJDK 8 JVMs.

Works on OpenJDK 9+ JVMs, but requires the following JVM args:

 --add-opens java.base/sun.nio.ch=com.metsci.glimpse.util
 --add-opens java.base/jdk.internal.ref=com.metsci.glimpse.util
 

Use with caution. Deallocating a buffer inappropriately can crash the JVM (or even worse, conceivably).

Constructor Summary

Constructors

Constructor	Description
DirectBufferDealloc()

Method Summary

Modifier and Type	Method	Description
static void	checkModuleAccess()
static void	deallocateDirectBuffer(Buffer directBuffer)
static void	deallocateDirectBuffers(Buffer... directBuffers)
static void	deallocateDirectBuffers(Collection<? extends Buffer> directBuffers)

Methods inherited from class java.lang.Object

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

Constructor Detail

DirectBufferDealloc

public DirectBufferDealloc()

Method Detail

checkModuleAccess

public static void checkModuleAccess()

deallocateDirectBuffer

public static void deallocateDirectBuffer(Buffer directBuffer)

deallocateDirectBuffers

public static void deallocateDirectBuffers(Buffer... directBuffers)

deallocateDirectBuffers

public static void deallocateDirectBuffers(Collection<? extends Buffer> directBuffers)