Garbage Collector Parameters Summary

Parameters	Description
-xx:+useserialgc	The JVM runs the default value in client mode, and after this switch is turned on, memory recycling is performed using the collector combination of Serial + Serial old
-xx:+useparnewgc	After you turn on this switch, use Parnew + Serial old collector for garbage collection
-xx:+useconcmarksweepgc	Using parnew + cms + Serial old collector combination for memory reclamation, Serial old as the CMS "Concurrent Mode Failure" After the failure of the fallback collector.
-xx:+useparallelgc	The JVM runs the default value in Server mode, and when this switch is turned on, it is recycled using the collector combination of parallel scavenge + Serial old
-xx:+useparalleloldgc	Recycling with collector combinations of Parallel scavenge + Parallel old
-xx:survivorratio	The capacity ratio of the Eden region to the survivor region in the Cenozoic, the default is 8, which represents eden:subrvivor = 8:1
-xx:pretenuresizethreshold	Directly promoted to the size of the old age object, after setting this parameter, objects larger than this parameter will be allocated directly in the old age
-xx:maxtenuringthreshold	Promotion to the age of the old, each time after minor GC, the age of 1, when the value of this parameter to enter the old age
-xx:useadaptivesizepolicy	Dynamically adjusts the size of each area in the Java heap and the age of entry into the old age
-xx:+handlepromotionfailure	Whether to allow the new generation to collect the guarantee, once minor GC, another piece of survivor space is not enough, will be directly in the old age to retain
-xx:parallelgcthreads	Set the number of threads in a parallel GC for memory reclamation
-xx:gctimeratio	GC time is the column of the total time, the default value is 99, which is to allow 1% GC time, only valid when using the parallel scavenge collector
-xx:maxgcpausemillis	Set maximum pause time for GC, valid under parallel scavenge collector
-xx:cmsinitiatingoccupancyfraction	Set the CMS collector to start garbage collection after the old age space is used, the default value is 68%, only valid in the CMS collector,-xx:cmsinitiatingoccupancyfraction=70
-xx:+usecmscompactatfullcollection	Because the CMS collector is fragmented, this parameter sets whether a memory defragmentation process is required after the garbage collector, only valid when the CMS collector
-xx:+cmsfullgcbeforecompaction	Set up a CMS collector to perform a memory defragmentation process after several garbage collections, usually with the usecmscompactatfullcollection parameter
-xx:+usefastaccessormethods	Original type optimization
-xx:+disableexplicitgc	Whether to turn off manual System.GC
-xx:+cmsparallelremarkenabled	Reduce Mark pauses
-xx:largepagesizeinbytes	The size of the memory page cannot be set too large, affecting the size of the perm,-xx:largepagesizeinbytes=128m

Client, Server mode default GC

New

	generation GC mode	old age and persistent GC mode
Client	Serial Serial GC	Serial Old serial GC
Server	Parallel Scavenge Parallel Recovery GC	Parallel Old parallel GC

Sun/oracle JDK GC Combination method

New

	generation GC mode	old age and persistent GC mode
-xx:+useserialgc	Serial Serial GC	Serial Old serial GC
-xx:+useparallelgc	Parallel Scavenge Parallel Recovery GC	Serial Old parallel GC
-xx:+useconcmarksweepgc	Parnew Parallel GC	CMS concurrency GC When "Concurrent Mode Failure" appears Using the serial old serial GC
-xx:+useparnewgc	Parnew Parallel GC	Serial Old serial GC
-xx:+useparalleloldgc	Parallel Scavenge Parallel Recovery GC	Parallel Old parallel GC
-xx:+useconcmarksweepgc -xx:+useparnewgc	Serial Serial GC	CMS concurrency GC When "Concurrent Mode Failure" appears Using the serial old serial GC

Garbage Collector Parameters Summary