Some common instructions in JVM tuning

Set up a garbage collector

-XX:+UseSerialGC:                                            Using a serial collector
-XX:+UseParallelGC:                                        Use parallel collectors
-XX:+UseParalledlOldGC:                                Using parallel generation collectors
-XX:+UseConcMarkSweepGC                          Use CMS The collector

-XX:+UseG1GC                                                Use G1 The collector

Heap settings

-Xms:                                                         Initial heap size
-Xmx:                                                         Maximum heap size
-XX:NewSize=n:                                         Set the size of the new generation
-XX:NewRatio=n:                                         Set the ratio of young generation to old generation .

                                                                 Such as : by 3, The ratio of young generation to old generation is 1：3,
-XX:SurvivorRatio=n: Young generation Eden District and two Survivor Area ratio .

Be careful Survivor There are two. . Such as ：3, Express Eden：Survivor=3：2, One Survivor District accounts for the whole young generation 1/5
-XX:MaxPermSize=n:                                 Set persistent generation （ Meta space ） size

Garbage collector log

-XX:+PrintGC                             idea Output garbage collection information                          
-XX:+PrintGCDetails                  idea Output detailed garbage collection information  
-XX:+PrintGCTimeStamps
-Xloggc:D:\ nailing \1.txt (filename)  Print the log to the setting path

Parallel collector settings
-XX:ParallelGCThreads=n: Set the... Used by the parallel collector collection CPU Count . Number of parallel collection threads .
-XX:MaxGCPauseMillis=n: Set the maximum pause time for parallel collection （G1 Garbage collector can be used ）
-XX:GCTimeRatio=n: Set the percentage of garbage collection time in the running time of the program . Formula for 1/(1+n)

-XX:+UserAdaptiveSizePolicy Set up Parallel Scavenge The collector has an adaptive tuning strategy .

Concurrent collector settings
-XX:+CMSIncrementalMode: Set to incremental mode . Applicable to single CPU situation .
-XX:ParallelGCThreads=n: When setting the collection mode of the younger generation of the concurrent collector to parallel collection , The use of CPU Count . Number of parallel collection threads .

Judge OOM out of memory

-XX:+HeapDumpOnOutOfMemoryError

-XX:HeapDumpPath=d:\dump