Thanks Sergio - that's good advice and we have this built into the plan. Have you heard a solid/consistent recommendation/requirement as to the amount of memory heap requires for G1GC?
On Fri, Nov 1, 2019 at 5:11 PM Sergio <lapostadiser...@gmail.com> wrote: > In any case I would test with tlp-stress or Cassandra stress tool any > configuration > > Sergio > > On Fri, Nov 1, 2019, 12:31 PM Ben Mills <b...@bitbrew.com> wrote: > >> Greetings, >> >> We are planning a Cassandra upgrade from 3.7 to 3.11.5 and considering a >> change to the GC config. >> >> What is the minimum amount of memory that needs to be allocated to heap >> space when using G1GC? >> >> For GC, we currently use CMS. Along with the version upgrade, we'll be >> running the stateful set of Cassandra pods on new machine types in a new >> node pool with 12Gi memory per node. Not a lot of memory but an >> improvement. We may be able to go up to 16Gi memory per node. We'd like to >> continue using these heap settings: >> >> -XX:+UnlockExperimentalVMOptions >> -XX:+UseCGroupMemoryLimitForHeap >> -XX:MaxRAMFraction=2 >> >> which (if 12Gi per node) would provide 6Gi memory for heap (i.e. half of >> total available). >> >> Here are some details on the environment and configs in the event that >> something is relevant. >> >> Environment: Kubernetes >> Environment Config: Stateful set of 3 replicas >> Storage: Persistent Volumes >> Storage Class: SSD >> Node OS: Container-Optimized OS >> Container OS: Ubuntu 16.04.3 LTS >> Data Centers: 1 >> Racks: 3 (one per zone) >> Nodes: 3 >> Tokens: 4 >> Replication Factor: 3 >> Replication Strategy: NetworkTopologyStrategy (all keyspaces) >> Compaction Strategy: STCS (all tables) >> Read/Write Requirements: Blend of both >> Data Load: <1GB per node >> gc_grace_seconds: default (10 days - all tables) >> >> GC Settings: (CMS) >> >> -XX:+UseParNewGC >> -XX:+UseConcMarkSweepGC >> -XX:+CMSParallelRemarkEnabled >> -XX:SurvivorRatio=8 >> -XX:MaxTenuringThreshold=1 >> -XX:CMSInitiatingOccupancyFraction=75 >> -XX:+UseCMSInitiatingOccupancyOnly >> -XX:CMSWaitDuration=30000 >> -XX:+CMSParallelInitialMarkEnabled >> -XX:+CMSEdenChunksRecordAlways >> >> Any ideas are much appreciated. >> >
