Pat, You might find this post useful in tuning G1 for Cassandra:
* http://deliberate-thinking.blogspot.com/2019/05/tuning-g1-gc-for-cassandra.html This assumes a machine with 60-120G of RAM -- and your use case may be different than the clusters I've tuned, so take each step with care. Also, I have no experience tuning G1 over 31G of heap -- the JVM uses 8 byte pointers with a 32G+ heap. You can get a lot of read throughput with a 24G heap with a new size fixed at 8-10G, as long as your records aren't all huge blobs. John... ________________________________ From: p...@xvalheru.org <p...@xvalheru.org> Sent: Friday, September 6, 2019 3:00 AM To: user@cassandra.apache.org <user@cassandra.apache.org> Cc: Jeff Jirsa <jji...@gmail.com> Subject: Re: Cassandra JVM configuration - reads => as much as possible - huge stream of requests - data => 186GB on each node - the reads are unpredictable - there's (in the cluster) about 6 billions of records I'll try change the garbage collector. Thanks Pat On 2019-09-05 16:38, Jeff Jirsa wrote: > Lot of variables > > - how many reads per second per machine? > - how much data per machine? > - are the reads random or is there a hot working set? > > Some of the suggestions online are old. > CASSANDRA-8150 has some old’ish suggestions if you’re running CMS > collector. Running > 16G heap should consider using G1GC and that’s > tuned quite differently. Amy Tobey has a decent (2.1 era) tuning > guide, I imagine The Last Pickle has one as well (and wouldn’t be > surprised if Pythian and Instaclustr do too). > > > >> On Sep 5, 2019, at 7:04 AM, p...@xvalheru.org wrote: >> >> Hi, >> >> sorry to bring such question, but I want to ask what are the best JVM >> options for Cassandra node? In solution I'm implementing the Cassandra >> serves as read-only storage (of course populated at beginning) - the >> records are not changed in time. Currently each Cassandra node's VM >> has this configuration 16CPUs and 64GB of RAM. I've set these JVM >> options: -Xms4G and -Xmx40G; JDK 1.8.0_221. My question is what's the >> best size of memory for Cassandra node and if there's any relation >> between number of CPUs and memory size. When I've searched for an >> answer I've found that suggested size for node is 8GB of RAM, but I >> have doubts. >> >> Thanks >> >> Pat >> >> ---------------------------------------- >> Freehosting PIPNI - >> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.pipni.cz_&d=DwIDaQ&c=z0adcvxXWKG6LAMN6dVEqQ&r=W9UI0GQq10yOhf5LxSjoITGT9p69DtOfFK_UGgl4kx8&m=Twi1q-yZbM-7JseysmH7h_XO5CVH_qz-2rZkyrQ27zY&s=KB8dnJ9Hih2DBTUE5LHJNDQW5jpcUv9GPGwoC-03bmQ&e= >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org >> For additional commands, e-mail: user-h...@cassandra.apache.org >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org > For additional commands, e-mail: user-h...@cassandra.apache.org > > > ---------------------------------------- > Freehosting PIPNI - > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.pipni.cz_&d=DwIDaQ&c=z0adcvxXWKG6LAMN6dVEqQ&r=W9UI0GQq10yOhf5LxSjoITGT9p69DtOfFK_UGgl4kx8&m=Twi1q-yZbM-7JseysmH7h_XO5CVH_qz-2rZkyrQ27zY&s=KB8dnJ9Hih2DBTUE5LHJNDQW5jpcUv9GPGwoC-03bmQ&e= ---------------------------------------- Freehosting PIPNI - https://urldefense.proofpoint.com/v2/url?u=http-3A__www.pipni.cz_&d=DwIDaQ&c=z0adcvxXWKG6LAMN6dVEqQ&r=W9UI0GQq10yOhf5LxSjoITGT9p69DtOfFK_UGgl4kx8&m=Twi1q-yZbM-7JseysmH7h_XO5CVH_qz-2rZkyrQ27zY&s=KB8dnJ9Hih2DBTUE5LHJNDQW5jpcUv9GPGwoC-03bmQ&e= --------------------------------------------------------------------- To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org For additional commands, e-mail: user-h...@cassandra.apache.org
