JVM

jvm.options (enable G1 / disable CMS)

Configure your JVM to use G1 garbage collector. By default, jvm.options uses the older CMS garbage collector.

Note

Where is JVM configuration ? < 3.0.0: cassandra-env.sh & >= 3.0.0: jvm.options.

#################
#  GC SETTINGS  #
#################


### CMS Settings

-XX:+UseParNewGC
-XX:+UseConcMarkSweepGC
-XX:+CMSParallelRemarkEnabled
-XX:SurvivorRatio=8
-XX:MaxTenuringThreshold=1
-XX:CMSInitiatingOccupancyFraction=75
-XX:+UseCMSInitiatingOccupancyOnly
-XX:CMSWaitDuration=10000
-XX:+CMSParallelInitialMarkEnabled
-XX:+CMSEdenChunksRecordAlways
# some JVMs will fill up their heap when accessed via JMX, see CASSANDRA-6541
-XX:+CMSClassUnloadingEnabled

### G1 Settings (experimental, comment previous section and uncomment section below to enable)

## Use the Hotspot garbage-first collector.
#-XX:+UseG1GC
#
## Have the JVM do less remembered set work during STW, instead
## preferring concurrent GC. Reduces p99.9 latency.
#-XX:G1RSetUpdatingPauseTimePercent=5
#
## Main G1GC tunable: lowering the pause target will lower throughput and vise versa.
## 200ms is the JVM default and lowest viable setting
## 1000ms increases throughput. Keep it smaller than the timeouts in cassandra.yaml.
#-XX:MaxGCPauseMillis=500

## Optional G1 Settings
# Save CPU time on large (>= 16GB) heaps by delaying region scanning
# until the heap is 70% full. The default in Hotspot 8u40 is 40%.
#-XX:InitiatingHeapOccupancyPercent=70

# For systems with > 8 cores, the default ParallelGCThreads is 5/8 the number of logical cores.
# Otherwise equal to the number of cores when 8 or less.
# Machines with > 10 cores should try setting these to <= full cores.
#-XX:ParallelGCThreads=16
# By default, ConcGCThreads is 1/4 of ParallelGCThreads.
# Setting both to the same value can reduce STW durations.
#-XX:ConcGCThreads=16

### GC logging options -- uncomment to enable

-XX:+PrintGCDetails
-XX:+PrintGCDateStamps
-XX:+PrintHeapAtGC
-XX:+PrintTenuringDistribution
-XX:+PrintGCApplicationStoppedTime
-XX:+PrintPromotionFailure
#-XX:PrintFLSStatistics=1
#Xloggc:/var/log/cassandra/gc.log ← recommend you enable gc logging and rotate the logs
-XX:+UseGCLogFileRotation
-XX:NumberOfGCLogFiles=10
-XX:GCLogFileSize=10M