I still use ParNew + CMS over G1GC with Java 8. I haven't done a comparison with JDK 11 yet, so I'm not sure if it's any better. I've heard it is, but I like to verify first. The pause times with ParNew + CMS are generally lower than G1 when tuned right, but as Chris said it can be tricky. If you aren't willing to spend the time understanding how it works and why each setting matters, G1 is a better option.
I wouldn't run Cassandra in production on less than 8GB of heap - I consider it the absolute minimum. For G1 I'd use 16GB, and never 4GB with Cassandra unless you're rarely querying it. I typically use the following as a starting point now: ParNew + CMS 16GB heap 10GB new gen 2GB memtable cap, otherwise you'll spend a bunch of time copying around memtables (cassandra.yaml) Max tenuring threshold: 2 survivor ratio 6 I've also done some tests with a 30GB heap, 24 GB of which was new gen. This worked surprisingly well in my tests since it essentially keeps everything out of the old gen. New gen allocations are just a pointer bump and are pretty fast, so in my (limited) tests of this I was seeing really good p99 times. I was seeing a 200-400 ms pause roughly once a minute running a workload that deliberately wasn't hitting a resource limit (testing real world looking stress vs overwhelming the cluster). We built tlp-cluster [1] and tlp-stress [2] to help figure these things out. [1] https://thelastpickle.com/tlp-cluster/ [2] http://thelastpickle.com/tlp-stress Jon On Mon, Oct 21, 2019 at 10:24 AM Reid Pinchback <rpinchb...@tripadvisor.com> wrote: > 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> 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> > 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 > For additional commands, e-mail: user-h...@cassandra.apache.org > >
