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From Richard Wagg <>
Subject RE: Artems: ParallelGC vs CMS
Date Wed, 08 Feb 2017 10:09:58 GMT
CMS should not be used in incremental mode for any modern hardware  - see

Try the below, and take a look at what the GC log output shows?
-Xms8G -Xmx8G -XX:+UseConcMarkSweepGC  -XX:+UseParNewGC -XX:+CMSClassUnloadingEnabled -XX:MaxTenuringThreshold=8
-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/var/log/apps/activemq/

Extra args for GC logging
-XX:+PrintGCCause -XX:+PrintGCDetails  -XX:+PrintTenuringDistribution  -XX:+PrintGCTimeStamps
-XX:+PrintGCDateStamps -Xloggc:/var/log/apps/activemq/gclog.log

-----Original Message-----
From: abhijith []
Sent: 07 February 2017 18:53
Subject: Artems: ParallelGC vs CMS


Has there any test done for Artemis using CMS GC?

Context:  We were using default parallel GC with 6G RAM and were facing an issue where old
gen was filling up without full GC being run.  We use Netty Transport configuration and have
one master/slave setup with static configuration.  Our monitoring alerts for total memory
usage were firing.
So we ran some tests and found that old gen was growing very slowly in case of CMS, but very
rapidly in case of parallel GC.

We switched to using CMS, but after changing to CMS we started seeing connection errors when
session factory is trying to create a new connection.
This was happening consistently which forced us to roll back.  After rollback with parallel
gc we do not see this issue at all.  We are kind of confused on how selection of GC can affect
creating new connections.  Any insight would be really helpful.

GG parameters:  "-XX:+UseFastAccessorMethods -Xms8G -Xmx8G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode
-XX:CMSIncrementalDutyCycleMin=10 -XX:CMSIncrementalDutyCycle=20 -XX:+CMSIncrementalPacing
-XX:+CMSClassUnloadingEnabled "

Caused by:
AMQ119024: Could not select a TransportConfiguration to create SessionFactory
        ... 122 common frames omitted


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