-
- All Superinterfaces:
MemoryPoolMXBean
,PlatformManagedObject
- All Known Implementing Classes:
MemoryPoolMXBeanImpl
public interface MemoryPoolMXBean extends MemoryPoolMXBean
The OpenJ9 interface for managing and monitoring the virtual machine's memory pools. The following list describes 4 common behavior changes forMemoryPoolMXBean
. You can revert to the earlier implementation ofMemoryPoolMXBean
by setting the -XX:+HeapManagementMXBeanCompatibility Java command line option.1. More detailed heap memory pools can be obtained by calling
The following names are reported for heap memory pools, listed by garbage collection policy:ManagementFactory.getMemoryPoolMXBeans()
For -Xgcpolicy:gencon- nursery-allocate
- nursery-survivor
- tenured-LOA
- tenured-SOA
For -Xgcpolicy:optthruput and -Xgcpolicy:optavgpause- tenured-LOA
- tenured-SOA
For -Xgcpolicy:balanced- balanced-reserved
- balanced-eden
- balanced-survivor
- balanced-old
For -Xgcpolicy:metronome- JavaHeap
If you set the -XX:+HeapManagementMXBeanCompatibility option to turn on compatibility with earlier versions of the VM, information about heap memory pools is reported in the older format.
The following name is reported for the heap memory pool for all garbage collection policies in the old format:- Java heap
2. Memory Usage
Memory usage for each heap memory pool can be retrieved by usingMemoryPoolMXBean.getUsage()
orMemoryPoolMXBean.getCollectionUsage()
. In some cases the total sum of memory usage of all heap memory pools is more than the maximum heap size. This irregularity can be caused if data for each pool is collected between garbage collection cycles, where objects have been moved or reclaimed. If you want to collect memory usage data that is synchronized across the memory pools, use theGarbageCollectionNotificationInfo
orGarbageCollectorMXBean.getLastGcInfo()
extensions.3. Usage Threshold (
The usage threshold attribute is designed for monitoring the increasing trend of memory usage and incurs only a low overhead. This attribute is not appropriate for some memory pools. Use theMemoryPoolMXBean.getUsageThreshold()
,MemoryPoolMXBean.setUsageThreshold(long)
,MemoryPoolMXBean.isUsageThresholdExceeded()
)MemoryPoolMXBean.isUsageThresholdSupported()
method to determine if this functionality is supported by the memory pool to avoid an unexpectedUnsupportedOperationException
.
The following names are reported for heap memory pools that support the usage threshold attribute:- JavaHeap
- tenured
- tenured-LOA
- tenured-SOA
- balanced-survivor
- balanced-old
4. Collection Usage Threshold (
The collection usage threshold is a manageable attribute that is applicable only to some garbage-collected memory pools. This attribute reports the amount of memory taken up by objects that are still in use after a garbage collection cycle. Use theMemoryPoolMXBean.getCollectionUsageThreshold()
,MemoryPoolMXBean.setCollectionUsageThreshold(long)
,MemoryPoolMXBean.isCollectionUsageThresholdExceeded()
)MemoryPoolMXBean.isCollectionUsageThresholdSupported()
method to determine if this functionality is supported by the memory pool to avoid an unexpectedUnsupportedOperationException
.
The following names are reported for heap memory pools that support the collection usage threshold attribute:- JavaHeap
- tenured
- tenured-LOA
- tenured-SOA
- nursery-allocate
- balanced-eden
- balanced-survivor
- balanced-old
- Since:
- 1.5
-
-
Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description MemoryUsage
getPreCollectionUsage()
If supported by the virtual machine, returns aMemoryUsage
which encapsulates this memory pool's memory usage before the most recent run of the garbage collector.-
Methods declared in interface java.lang.management.MemoryPoolMXBean
getCollectionUsage, getCollectionUsageThreshold, getCollectionUsageThresholdCount, getMemoryManagerNames, getName, getPeakUsage, getType, getUsage, getUsageThreshold, getUsageThresholdCount, isCollectionUsageThresholdExceeded, isCollectionUsageThresholdSupported, isUsageThresholdExceeded, isUsageThresholdSupported, isValid, resetPeakUsage, setCollectionUsageThreshold, setUsageThreshold
-
Methods declared in interface java.lang.management.PlatformManagedObject
getObjectName
-
-
-
-
Method Detail
-
getPreCollectionUsage
MemoryUsage getPreCollectionUsage()
If supported by the virtual machine, returns aMemoryUsage
which encapsulates this memory pool's memory usage before the most recent run of the garbage collector. No garbage collection will be actually occur as a result of this method getting called.The method will return a
MBeanServer access:null
if the virtual machine does not support this type of functionality.
The return value will be mapped to aCompositeData
with attributes as specified inMemoryUsage
.- Returns:
- a
MemoryUsage
containing the usage details for the memory pool just before the most recent collection occurred.
-
-