| ########################################################################### |
| # jvm.options # |
| # # |
| # - all flags defined here will be used by cassandra to startup the JVM # |
| # - one flag should be specified per line # |
| # - lines that do not start with '-' will be ignored # |
| # - only static flags are accepted (no variables or parameters) # |
| # - dynamic flags will be appended to these on cassandra-env # |
| ########################################################################### |
| |
| ################# |
| # HEAP SETTINGS # |
| ################# |
| |
| # Heap size is automatically calculated by cassandra-env based on this |
| # formula: max(min(1/2 ram, 1024MB), min(1/4 ram, 8GB)) |
| # That is: |
| # - calculate 1/2 ram and cap to 1024MB |
| # - calculate 1/4 ram and cap to 8192MB |
| # - pick the max |
| # |
| # For production use you may wish to adjust this for your environment. |
| # If that's the case, uncomment the -Xmx and Xms options below to override the |
| # automatic calculation of JVM heap memory. |
| # |
| # It is recommended to set min (-Xms) and max (-Xmx) heap sizes to |
| # the same value to avoid stop-the-world GC pauses during resize, and |
| # so that we can lock the heap in memory on startup to prevent any |
| # of it from being swapped out. |
| #-Xms4G |
| #-Xmx4G |
| |
| # Young generation size is automatically calculated by cassandra-env |
| # based on this formula: min(100 * num_cores, 1/4 * heap size) |
| # |
| # The main trade-off for the young generation is that the larger it |
| # is, the longer GC pause times will be. The shorter it is, the more |
| # expensive GC will be (usually). |
| # |
| # It is not recommended to set the young generation size if using the |
| # G1 GC, since that will override the target pause-time goal. |
| # More info: http://www.oracle.com/technetwork/articles/java/g1gc-1984535.html |
| # |
| # The example below assumes a modern 8-core+ machine for decent |
| # times. If in doubt, and if you do not particularly want to tweak, go |
| # 100 MB per physical CPU core. |
| #-Xmn800M |
| |
| ################################### |
| # EXPIRATION DATE OVERFLOW POLICY # |
| ################################### |
| |
| # Defines how to handle INSERT requests with TTL exceeding the maximum supported expiration date: |
| # * REJECT: this is the default policy and will reject any requests with expiration date timestamp after 2038-01-19T03:14:06+00:00. |
| # * CAP: any insert with TTL expiring after 2038-01-19T03:14:06+00:00 will expire on 2038-01-19T03:14:06+00:00 and the client will receive a warning. |
| # * CAP_NOWARN: same as previous, except that the client warning will not be emitted. |
| # |
| #-Dcassandra.expiration_date_overflow_policy=REJECT |
| |
| ################# |
| # 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 |
| -XX:+UseGCLogFileRotation |
| -XX:NumberOfGCLogFiles=10 |
| -XX:GCLogFileSize=10M |