Java OpenJDK 8

This page describes the Optimization Pack for Java OpenJDK 8 JVM.

Metrics

Memory

Metric	Unit	Description
mem_used	bytes	The total amount of memory used
jvm_heap_size	bytes	The size of the JVM heap memory
jvm_heap_used	bytes	The amount of heap memory used
jvm_heap_util	percent	The utilization % of heap memory
jvm_off_heap_used	bytes	The amount of non-heap memory used
jvm_heap_old_gen_used	bytes	The amount of heap memory used (old generation)
jvm_heap_young_gen_used	bytes	The amount of heap memory used (young generation)
jvm_heap_old_gen_size	bytes	The size of the JVM heap memory (old generation)
jvm_heap_young_gen_size	bytes	The size of the JVM heap memory (young generation)
jvm_memory_used	bytes	The total amount of memory used across all the JVM memory pools
jvm_heap_committed	bytes	The size of the JVM committed memory
jvm_memory_buffer_pool_used	bytes	The total amount bytes used by buffers within the JVM buffer memory pool

CPU

Metric	Unit	Description
cpu_util	percent	The average CPU utilization % across all the CPUs (i.e., how much time on average the CPUs are busy doing work)
cpu_used	CPUs	The total amount of CPUs used

Garbage Collection

Metric	Unit	Description
jvm_gc_time	percent	The % of wall clock time the JVM spent doing stop the world garbage collection activities
jvm_gc_count	collections/s	The total number of stop the world JVM garbage collections that have occurred per second
jvm_gc_duration	seconds	The average duration of a stop the world JVM garbage collection

Other metrics

Metric	Unit	Description
jvm_threads_current	threads	The total number of active threads within the JVM
jvm_threads_deadlocked	threads	The total number of deadlocked threads within the JVM
jvm_compilation_time	milliseconds	The total time spent by the JVM JIT compiler compiling bytecode

Parameters

Memory

Name	Type	Unit	Dafault	Domain	Restart	Description
jvm_minHeapSize	integer	megabytes	You should select your own default value.	You should select your own domain.	yes	The minimum heap size.
jvm_maxHeapSize	integer	megabytes	You should select your own default value.	You should select your own domain.	yes	The maximum heap size.
jvm_maxRAM	integer	megabytes	You should select your own default value.	You should select your own domain.	yes	The maximum amount of memory used by the JVM.
jvm_initialRAMPercentage	real	percent	1.563	0.1 → 100	yes	The initial percentage of memory used by the JVM.
jvm_maxRAMPercentage	real	percent	25.0	0.1 → 100.0	yes	The percentage of memory used for maximum heap size, on systems with large physical memory size (more than 512MB). Requires Java 10, Java 8 Update 191 or later.
jvm_alwaysPreTouch	categorical		-AlwaysPreTouch	+AlwaysPreTouch, -AlwaysPreTouch	yes	Pretouch pages during initialization.
jvm_metaspaceSize	integer	megabytes	20	You should select your own domain within 1 and 1024	yes	The initial size of the allocated class metadata space.
jvm_maxMetaspaceSize	integer	megabytes	20	You should select your own domain within 1 and 1024	yes	The maximum size of the allocated class metadata space.
jvm_useTransparentHugePages	categorical		-UseTransparentHugePages	+UseTransparentHugePages, -UseTransparentHugePages	yes	Enables the use of large pages that can dynamically grow or shrink.
jvm_allocatePrefetchInstr	integer		0	0 → 3	yes	Prefetch ahead of the allocation pointer.
jvm_allocatePrefetchDistance	integer	bytes	0	0 → 512	yes	Distance to prefetch ahead of allocation pointer. -1 use system-specific value (automatically determined).
jvm_allocatePrefetchLines	integer	lines	3	1 → 64	yes	The number of lines to prefetch ahead of array allocation pointer.
jvm_allocatePrefetchStyle	integer		1	0 → 3	yes	Selects the prefetch instruction to generate.
jvm_useLargePages	categorical		+UseLargePages	+UseLargePages, -UseLargePages	yes	Enable the use of large page memory.

Garbage Collection

Name	Type	Unit	Default	Domain	Restart	Description
jvm_newRatio	integer		2	0 → 2147483647	yes	The ratio of old/new generation sizes.
jvm_newSize	integer	megabytes	You should select your own default value.	You should select your own domain.	yes	Sets the initial and maximum size of the heap for the young generation (nursery).
jvm_maxNewSize	integer	megabytes	You should select your own default value.	You should select your own domain.	yes	Specifies the upper bound for the young generation size.
jvm_survivorRatio	integer		8	1 → 100	yes	The ratio between the Eden and each Survivor-space within the JVM. For example, a jvm_survivorRatio would mean that the Eden-space is 6 times one Survivor-space.
jvm_useAdaptiveSizePolicy	categorical		+UseAdaptiveSizePolicy	+UseAdaptiveSizePolicy, -UseAdaptiveSizePolicy	yes	Enable adaptive generation sizing. Disable coupled with jvm_targetSurvivorRatio.
jvm_adaptiveSizePolicyWeight	integer		10	0 → 100	yes	The weighting given to the current Garbage Collection time versus previous GC times when checking the timing goal.
jvm_targetSurvivorRatio	integer		50	1 → 100	yes	The desired percentage of Survivor-space used after young garbage collection.
jvm_minHeapFreeRatio	integer		40	1 → 99	yes	The minimum percentage of heap free after garbage collection to avoid shrinking.
jvm_maxHeapFreeRatio	integer		70	0 → 100	yes	The maximum percentage of heap free after garbage collection to avoid shrinking.
jvm_maxTenuringThreshold	integer		15	0 → 15	yes	The maximum value for the tenuring threshold.
jvm_gcType	categorical		Parallel	Serial, Parallel, ConcMarkSweep, G1, ParNew	yes	Type of the garbage collection algorithm.
jvm_concurrentGCThreads	integer	threads	You should select your own default value.	You should select your own domain.	yes	The number of threads concurrent garbage collection will use.
jvm_parallelGCThreads	integer	threads	You should select your own default value.	You should select your own domain.	yes	The number of threads garbage collection will use for parallel phases.
jvm_maxGCPauseMillis	integer	milliseconds	200	1 → 1000	yes	Adaptive size policy maximum GC pause time goal in millisecond.
jvm_resizePLAB	categorical		+ResizePLAB	+ResizePLAB, -ResizePLAB	yes	Enables the dynamic resizing of promotion LABs.
jvm_GCTimeRatio	integer		99	0 → 100	yes	The target fraction of time that can be spent in garbage collection before increasing the heap, computet as 1 / (1 + GCTimeRatio).
jvm_initiatingHeapOccupancyPercent	integer		45	0 → 100	yes	Sets the percentage of the heap occupancy at which to start a concurrent GC cycle.
jvm_youngGenerationSizeIncrement	integer		20	0 → 100	yes	The increment size for Young Generation adaptive resizing.
jvm_tenuredGenerationSizeIncrement	integer		20	0 → 100	yes	The increment size for Old/Tenured Generation adaptive resizing.
jvm_adaptiveSizeDecrementScaleFactor	integer		4	1 → 1024	yes	Specifies the scale factor for goal-driven generation resizing.
jvm_CMSTriggerRatio	integer		80	0 → 100	yes	The percentage of MinHeapFreeRatio allocated before CMS GC starts
jvm_CMSInitiatingOccupancyFraction	integer		-1	-1 → 99	yes	Configure oldgen occupancy fraction threshold for CMS GC. Negative values default to CMSTriggerRatio.
jvm_CMSClassUnloadingEnabled	categorical		+CMSClassUnloadingEnabled	+CMSClassUnloadingEnabled, -CMSClassUnloadingEnabled	yes	Enables class unloading when using CMS.
jvm_useCMSInitiatingOccupancyOnly	categorical		-UseCMSInitiatingOccupancyOnly	+UseCMSInitiatingOccupancyOnly, -UseCMSInitiatingOccupancyOnly	yes	Use of the occupancy value as the only criterion for initiating the CMS collector.
jvm_G1HeapRegionSize	integer	megabytes	8	1→32	yes	Sets the size of the regions for G1.
jvm_G1ReservePercent	integer		10	0 → 50	yes	Sets the percentage of the heap that is reserved as a false ceiling to reduce the possibility of promotion failure for the G1 collector.
jvm_G1NewSizePercent	integer		5	0 → 100	yes	Sets the percentage of the heap to use as the minimum for the young generation size.
jvm_G1MaxNewSizePercent	integer		60	0 → 100	yes	Sets the percentage of the heap size to use as the maximum for young generation size.
jvm_G1MixedGCLiveThresholdPercent	integer		85	0 → 100	yes	Sets the occupancy threshold for an old region to be included in a mixed garbage collection cycle.
jvm_G1HeapWastePercent	integer		5	0 → 100	yes	The maximum percentage of the reclaimable heap before starting mixed GC.
jvm_G1MixedGCCountTarget	integer	collections	8	0 → 100	yes	Sets the target number of mixed garbage collections after a marking cycle to collect old regions with at most G1MixedGCLIveThresholdPercent live data. The default is 8 mixed garbage collections.
jvm_G1OldCSetRegionThresholdPercent	integer		10	0 → 100	yes	The upper limit on the number of old regions to be collected during mixed GC.

Compilation

Name	Type	Unit	Default	Domain	Restart	Description
jvm_reservedCodeCacheSize	integer	megabytes	240	3 → 2048	yes	The maximum size of the compiled code cache pool.
jvm_tieredCompilation	categorical		+TieredCompilation	+TieredCompilation, -TieredCompilation	yes	The type of the garbage collection algorithm.
jvm_tieredCompilationStopAtLevel	integer		4	0 → 4	yes	Overrides the number of detected CPUs that the VM will use to calculate the size of thread pools.
jvm_compilationThreads	integer	threads	You should select your own default value.	You should select your own domain.	yes	The number of compilation threads.
jvm_backgroundCompilation	categorical		+BackgroundCompilation	+BackgroundCompilation, -BackgroundCompilation	yes	Allow async interpreted execution of a method while it is being compiled.
jvm_inline	categorical		+Inline	+Inline, -Inline	yes	Enable inlining.
jvm_maxInlineSize	integer	bytes	35	1 → 2097152	yes	The bytecode size limit (in bytes) of the inlined methods.
jvm_inlineSmallCode	integer	bytes	2000	1 → 16384	yes	The maximum compiled code size limit (in bytes) of the inlined methods.

Other parameters

Name	Type	Unit	Default	Domain	Restart	Description
jvm_aggressiveOpts	categorical		-AggressiveOpts	+AggressiveOpts, -AggressiveOpts	yes	Turn on point performance compiler optimizations.
jvm_usePerfData	categorical		+UsePerfData	+UsePerfData, -UsePerfData	yes	Enable monitoring of performance data.
jvm_useNUMA	categorical		-UseNUMA	+UseNUMA, -UseNUMA	yes	Enable NUMA.
jvm_useBiasedLocking	categorical		+UseBiasedLocking	+UseBiasedLocking, -UseBiasedLocking	yes	Manage the use of biased locking.
jvm_activeProcessorCount	integer	CPUs	1	1 → 512	yes	Overrides the number of detected CPUs that the VM will use to calculate the size of thread pools.

Domains

The following parameters require their ranges or default values to be updated according to the described rules:

Parameter	Default value	Domain
jvm_minHeapSize		Depends on the instance available memory
jvm_maxHeapSize		Depends on the instance available memory
jvm_newSize		Depends on the configured heap
jvm_maxNewSize		Depends on the configured heap
jvm_concurrentGCThreads	Depends on the available CPU cores	Depends on the available CPU cores
jvm_parallelGCThreads	Depends on the available CPU cores	Depends on the available CPU cores
jvm_compilation_threads	Depends on the available CPU cores	Depends on the available CPU cores

Constraints

The following tables show a list of constraints that may be required in the definition of the study, depending on the tuned parameters:

Formula	Notes
jvm.jvm_minHeapSize <= jvm.jvm_maxHeapSize
jvm.jvm_minHeapFreeRatio <= jvm.jvm_maxHeapFreeRatio
jvm.jvm_maxNewSize < jvm.jvm_maxHeapSize
jvm.jvm_concurrentGCThreads <= jvm.jvm_parallelGCThreads