java.lang.Object
- it.unich.jgmp.AllocationMonitor

```
public class AllocationMonitor
extends java.lang.Object
```
The allocation monitor keeps track of the amount of native memory allocated by GMP, and calls the Java garbage collector when it finds that too much native memory is being used. The hope is that, by destroying JGMP objects, the pressure on native memory is reduced.
In order to keep track of allocated native memory, this class uses the GMP fuctions mp_set_memory_functions and mp_get_memory_functions (see the Custom Allocation page of the GMP manual). Since this slows down allocation, the feature is normally disabled and may be enable by calling the enable() static method.
It is important to enable allocation monitor when a program builds many big JGMP objects. In this case, since the size occupied by a JGMP object in the Java heap is only a fraction of the size occupied in native memory, the program may consume all the native memory without the JVM feeling the need to call the garbage collector to reclaim heap space. This may happen, in particular, when making use of the immutable API.
The current allocator has three tunables: allocationThreshold, lowerThreshold and maxTimeout. Every allocation or reallocation of native memory by the GMP library makes the allocated size larger than the allocation threshold, causes a call to the Java garabage collector. Then, we wait until the allocated memory falls below the lower threshold, or until a timeout has expired. The length of the timeout is dinamically computed by the allocation monitor, but it never exceed the value of the maxTimeout tunable.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`private static class`	`AllocationMonitor.JGMPAlloc`	The custom allocator function.
`private static class`	`AllocationMonitor.JGMPFree`	The custom deallocator.
`private static class`	`AllocationMonitor.JGMPRealloc`	The custom reallocator.

Field Summary

Fields
Modifier and Type	Field	Description
`private static AllocFunc`	`af`
`private static AllocFuncByReference`	`afpOld`
`private static java.util.concurrent.atomic.AtomicLong`	`allocatedSize`	The amount of native memory allocated by GMP, as recorded by the allocation monitor.
`private static long`	`allocationThreshold`	The allocation threshold.
`private static int`	`debugLevel`	The debug level of the allocation monitor.
`private static FreeFunc`	`ff`
`private static FreeFuncByReference`	`ffpOld`
`private static int`	`gcCalls`	Keep track of the number of times that GC has been called by the allocation monitor.
`private static long`	`lowerThreshold`	The lower threshold.
`private static long`	`maxAllocatedSize`	The maximum amount of memory allocated by GMP.
`private static int`	`maxStepTimeout`	The maximum delay for a single timeout step.
`private static ReallocFunc`	`rf`
`private static ReallocFuncByReference`	`rfpOld`
`private static int`	`stepTimeout`	The current delay for a single timeout step.
`private static int`	`TIMEOUT_STEPS`	Number of steps in which we divide the timeout interval.

Constructor Summary

Constructors
Modifier Constructor Description

private AllocationMonitor()
A private constructor, since this class should never be instantiated.

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`(package private) static void`	`checkGC(long increase)`	Check if the garbage collector needs to be invoked, and update the numCrossed and allocation thresholds.
`private static void`	`debugInfo()`	Print debugging information.
`static void`	`disable()`	Disable the allocation monitor.
`static void`	`enable()`	Enable the allocation monitor.
`static long`	`getAllocatedSize()`	Return the amount of native memory allocated by JGMP, as recorded by the allocation monitor.
`static long`	`getAllocationThreshold()`	Return the current allocation threshold.
`static int`	`getDebugLevel()`	Return the current debug level of the allocation monitor.
`static int`	`getGcCalls()`	Return the number of times that GC has been called by the allocation monitor.
`static long`	`getLowerThreshold()`	Return the current value of the lower threshold.
`static long`	`getMaxAllocatedSize()`	Return the maximum amount of memory ever allocated by the JGMP at the same moment, as recorded by the allocation monitor.
`static int`	`getTimeout()`	Return the current timeout value.
`static void`	`setAllocationThreshold(long value)`	Set the current allocation threshold.
`static void`	`setDebugLevel(int debugLevel)`	Set the debug level of the allocation monitor.
`static void`	`setLowerThreshold(long value)`	Set the current value of the lower threshold.
`static void`	`setTimeout(int value)`	Set the maximum timeout value.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - debugLevel
```
private static volatile int debugLevel
```
    The debug level of the allocation monitor.
  - allocatedSize
```
private static java.util.concurrent.atomic.AtomicLong allocatedSize
```
    The amount of native memory allocated by GMP, as recorded by the allocation monitor. It is an `AtomicLong` since it might be increased concurrently by multple threads.
  - allocationThreshold
```
private static volatile long allocationThreshold
```
    The allocation threshold.
  - lowerThreshold
```
private static volatile long lowerThreshold
```
    The lower threshold.
  - TIMEOUT_STEPS
```
private static final int TIMEOUT_STEPS
```
    Number of steps in which we divide the timeout interval.
    
    See Also:
    
    Constant Field Values
  - maxStepTimeout
```
private static volatile int maxStepTimeout
```
    The maximum delay for a single timeout step.
  - stepTimeout
```
private static volatile int stepTimeout
```
    The current delay for a single timeout step.
  - gcCalls
```
private static volatile int gcCalls
```
    Keep track of the number of times that GC has been called by the allocation monitor.
  - maxAllocatedSize
```
private static volatile long maxAllocatedSize
```
    The maximum amount of memory allocated by GMP.
  - af
```
private static AllocFunc af
```
  - rf
```
private static ReallocFunc rf
```
  - ff
```
private static FreeFunc ff
```
  - afpOld
```
private static AllocFuncByReference afpOld
```
  - rfpOld
```
private static ReallocFuncByReference rfpOld
```
  - ffpOld
```
private static FreeFuncByReference ffpOld
```
- Constructor Detail
  - AllocationMonitor
```
private AllocationMonitor()
```
    A private constructor, since this class should never be instantiated.
- Method Detail
  - setDebugLevel
```
public static void setDebugLevel(int debugLevel)
```
    Set the debug level of the allocation monitor. The greater the value, the more debug messages are sent to the standard error. Zero and negative numbers mean that no debug messages are generated.
  - getDebugLevel
```
public static int getDebugLevel()
```
    Return the current debug level of the allocation monitor.
  - getAllocatedSize
```
public static long getAllocatedSize()
```
    Return the amount of native memory allocated by JGMP, as recorded by the allocation monitor.
  - getAllocationThreshold
```
public static long getAllocationThreshold()
```
    Return the current allocation threshold.
  - setAllocationThreshold
```
public static void setAllocationThreshold(long value)
```
    Set the current allocation threshold. This method also sets the default value for the lower threshold, which is 15/16 of the allocation threshold.
  - getLowerThreshold
```
public static long getLowerThreshold()
```
    Return the current value of the lower threshold.
  - setLowerThreshold
```
public static void setLowerThreshold(long value)
```
    Set the current value of the lower threshold.
  - setTimeout
```
public static void setTimeout(int value)
```
    Set the maximum timeout value. The default value is 200 ms.
  - getTimeout
```
public static int getTimeout()
```
    Return the current timeout value.
  - getGcCalls
```
public static int getGcCalls()
```
    Return the number of times that GC has been called by the allocation monitor.
  - getMaxAllocatedSize
```
public static long getMaxAllocatedSize()
```
    Return the maximum amount of memory ever allocated by the JGMP at the same moment, as recorded by the allocation monitor.
  - debugInfo
```
private static void debugInfo()
```
    Print debugging information.
  - checkGC
```
static void checkGC(long increase)
```
    Check if the garbage collector needs to be invoked, and update the numCrossed and allocation thresholds.
  - enable
```
public static void enable()
```
    Enable the allocation monitor. Nothing happens if the monitor is already enabled.
  - disable
```
public static void disable()
```
    Disable the allocation monitor. Nothing happens if the monitor is already disabled.

Class AllocationMonitor

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

debugLevel

allocatedSize

allocationThreshold

lowerThreshold

TIMEOUT_STEPS

maxStepTimeout

stepTimeout

gcCalls

maxAllocatedSize

af

rf

ff

afpOld

rfpOld

ffpOld

Constructor Detail

AllocationMonitor

Method Detail

setDebugLevel

getDebugLevel

getAllocatedSize

getAllocationThreshold

setAllocationThreshold

getLowerThreshold

setLowerThreshold

setTimeout

getTimeout

getGcCalls

getMaxAllocatedSize

debugInfo

checkGC

enable

disable