org.iq80.leveldb.fileenv

Class MmapLimiter

java.lang.Object

org.iq80.leveldb.fileenv.MmapLimiter

public final class MmapLimiter
extends Object

Helper class to limit mmap file usage so that we do not end up running out virtual memory or running into kernel performance problems for very large databases.

Field Summary

Fields

Modifier and Type	Field and Description
static int	CPU_DATA_MODEL
static boolean	USE_MMAP We only use MMAP on 64 bit systems since it's really easy to run out of virtual address space on a 32 bit system when all the data is getting mapped into memory.

Method Summary

Modifier and Type	Method and Description
boolean	acquire() If another mmap slot is available, acquire it and return true.
static MmapLimiter	defaultLimiter() Up to 1000 mmaps for 64-bit JVM; none for 32bit.
static MmapLimiter	newLimiter(int maxAllowedMmap)
void	release() Release a slot acquired by a previous call to Acquire() that returned true.

Methods inherited from class java.lang.Object

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

Field Detail

CPU_DATA_MODEL

public static final int CPU_DATA_MODEL

USE_MMAP

public static final boolean USE_MMAP

We only use MMAP on 64 bit systems since it's really easy to run out of virtual address space on a 32 bit system when all the data is getting mapped into memory. If you really want to use MMAP anyways, use -Dleveldb.mmap=true

Method Detail

defaultLimiter

public static MmapLimiter defaultLimiter()

Up to 1000 mmaps for 64-bit JVM; none for 32bit.

newLimiter

public static MmapLimiter newLimiter(int maxAllowedMmap)

acquire

public boolean acquire()

If another mmap slot is available, acquire it and return true. Else return false.

release

public void release()

Release a slot acquired by a previous call to Acquire() that returned true.