An i3x large has 30.5 gb of RAM but you’re using less than 4gb for C*. So minus room for other uses of jvm memory and for kernel activity, that’s about 25 gb for file cache. You’ll have to see if you either want a bigger heap to allow for less frequent gc cycles, or you could save money on the instance size. C* generates a lot of medium-length lifetime objects which can easily end up in old gen. A larger heap will reduce the burn of more old-gen collections. There are no magic numbers to just give because it’ll depend on your usage patterns.
From: Sergio <lapostadiser...@gmail.com> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org> Date: Sunday, October 20, 2019 at 2:51 PM To: "user@cassandra.apache.org" <user@cassandra.apache.org> Subject: Re: GC Tuning https://thelastpickle.com/blog/2018/04/11/gc-tuning.html Message from External Sender Thanks for the answer. This is the JVM version that I have right now. openjdk version "1.8.0_161" OpenJDK Runtime Environment (build 1.8.0_161-b14) OpenJDK 64-Bit Server VM (build 25.161-b14, mixed mode) These are the current flags. Would you change anything in a i3x.large aws node? java -Xloggc:/var/log/cassandra/gc.log -Dcassandra.max_queued_native_transport_requests=4096 -ea -XX:+UseThreadPriorities -XX:ThreadPriorityPolicy=42 -XX:+HeapDumpOnOutOfMemoryError -Xss256k -XX:StringTableSize=1000003 -XX:+AlwaysPreTouch -XX:-UseBiasedLocking -XX:+UseTLAB -XX:+ResizeTLAB -XX:+UseNUMA -XX:+PerfDisableSharedMem -Djava.net.preferIPv4Stack=true -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=1 -XX:+UseG1GC -XX:G1RSetUpdatingPauseTimePercent=5 -XX:MaxGCPauseMillis=200 -XX:InitiatingHeapOccupancyPercent=45 -XX:G1HeapRegionSize=0 -XX:-ParallelRefProcEnabled -Xms3821M -Xmx3821M -XX:CompileCommandFile=/etc/cassandra/conf/hotspot_compiler -Dcom.sun.management.jmxremote.port=7199 -Dcom.sun.management.jmxremote.rmi.port=7199 -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.password.file=/etc/cassandra/conf/jmxremote.password -Dcom.sun.management.jmxremote.access.file=/etc/cassandra/conf/jmxremote.access -Djava.library.path=/usr/share/cassandra/lib/sigar-bin -Djava.rmi.server.hostname=172.24.150.141 -XX:+CMSClassUnloadingEnabled -javaagent:/usr/share/cassandra/lib/jmx_prometheus_javaagent-0.3.1.jar=10100:/etc/cassandra/default.conf/jmx-export.yml -Dlogback.configurationFile=logback.xml -Dcassandra.logdir=/var/log/cassandra -Dcassandra.storagedir= -Dcassandra-pidfile=/var/run/cassandra/cassandra.pid -Dcassandra-foreground=yes -cp /etc/cassandra/conf:/usr/share/cassandra/lib/airline-0.6.jar:/usr/share/cassandra/lib/antlr-runtime-3.5.2.jar:/usr/share/cassandra/lib/asm-5.0.4.jar:/usr/share/cassandra/lib/caffeine-2.2.6.jar:/usr/share/cassandra/lib/cassandra-driver-core-3.0.1-shaded.jar:/usr/share/cassandra/lib/commons-cli-1.1.jar:/usr/share/cassandra/lib/commons-codec-1.9.jar:/usr/share/cassandra/lib/commons-lang3-3.1.jar:/usr/share/cassandra/lib/commons-math3-3.2.jar:/usr/share/cassandra/lib/compress-lzf-0.8.4.jar:/usr/share/cassandra/lib/concurrentlinkedhashmap-lru-1.4.jar:/usr/share/cassandra/lib/concurrent-trees-2.4.0.jar:/usr/share/cassandra/lib/disruptor-3.0.1.jar:/usr/share/cassandra/lib/ecj-4.4.2.jar:/usr/share/cassandra/lib/guava-18.0.jar:/usr/share/cassandra/lib/HdrHistogram-2.1.9.jar:/usr/share/cassandra/lib/high-scale-lib-1.0.6.jar:/usr/share/cassandra/lib/hppc-0.5.4.jar:/usr/share/cassandra/lib/jackson-core-asl-1.9.13.jar:/usr/share/cassandra/lib/jackson-mapper-asl-1.9.13.jar:/usr/share/cassandra/lib/jamm-0.3.0.jar:/usr/share/cassandra/lib/javax.inject.jar:/usr/share/cassandra/lib/jbcrypt-0.3m.jar:/usr/share/cassandra/lib/jcl-over-slf4j-1.7.7.jar:/usr/share/cassandra/lib/jctools-core-1.2.1.jar:/usr/share/cassandra/lib/jflex-1.6.0.jar:/usr/share/cassandra/lib/jmx_prometheus_javaagent-0.3.1.jar:/usr/share/cassandra/lib/jna-4.2.2.jar:/usr/share/cassandra/lib/joda-time-2.4.jar:/usr/share/cassandra/lib/json-simple-1.1.jar:/usr/share/cassandra/lib/jstackjunit-0.0.1.jar:/usr/share/cassandra/lib/libthrift-0.9.2.jar:/usr/share/cassandra/lib/log4j-over-slf4j-1.7.7.jar:/usr/share/cassandra/lib/logback-classic-1.1.3.jar:/usr/share/cassandra/lib/logback-core-1.1.3.jar:/usr/share/cassandra/lib/lz4-1.3.0.jar:/usr/share/cassandra/lib/metrics-core-3.1.5.jar:/usr/share/cassandra/lib/metrics-jvm-3.1.5.jar:/usr/share/cassandra/lib/metrics-logback-3.1.5.jar:/usr/share/cassandra/lib/netty-all-4.0.44.Final.jar:/usr/share/cassandra/lib/ohc-core-0.4.4.jar:/usr/share/cassandra/lib/ohc-core-j8-0.4.4.jar:/usr/share/cassandra/lib/reporter-config3-3.0.3.jar:/usr/share/cassandra/lib/reporter-config-base-3.0.3.jar:/usr/share/cassandra/lib/sigar-1.6.4.jar:/usr/share/cassandra/lib/slf4j-api-1.7.7.jar:/usr/share/cassandra/lib/snakeyaml-1.11.jar:/usr/share/cassandra/lib/snappy-java-1.1.1.7.jar:/usr/share/cassandra/lib/snowball-stemmer-1.3.0.581.1.jar:/usr/share/cassandra/lib/ST4-4.0.8.jar:/usr/share/cassandra/lib/stream-2.5.2.jar:/usr/share/cassandra/lib/thrift-server-0.3.7.jar:/usr/share/cassandra/apache-cassandra-3.11.3.jar:/usr/share/cassandra/apache-cassandra-thrift-3.11.3.jar:/usr/share/cassandra/stress.jar: org.apache.cassandra.service.CassandraDaemon Best, Sergio Il giorno sab 19 ott 2019 alle ore 14:30 Chris Lohfink <clohfin...@gmail.com<mailto:clohfin...@gmail.com>> ha scritto: "It depends" on your version and heap size but G1 is easier to get right so probably wanna stick with that unless you are using small heaps or really interested in tuning it (likely for massively smaller gains then tuning your data model). There is no GC algo that is strictly better than others in all scenarios unfortunately. If your JVM supports it, ZGC or Shenandoah are likely going to give you the best latencies. Chris On Fri, Oct 18, 2019 at 8:41 PM Sergio Bilello <lapostadiser...@gmail.com<mailto:lapostadiser...@gmail.com>> wrote: Hello! Is it still better to use ParNew + CMS Is it still better than G1GC these days? Any recommendation for i3.xlarge nodes read-heavy workload? Thanks, Sergio --------------------------------------------------------------------- To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org<mailto:user-unsubscr...@cassandra.apache.org> For additional commands, e-mail: user-h...@cassandra.apache.org<mailto:user-h...@cassandra.apache.org>
