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https://issues.apache.org/jira/browse/CASSANDRA-7432?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14089294#comment-14089294
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Joshua McKenzie commented on CASSANDRA-7432:
--------------------------------------------
Created CASSANDRA-7714 to track the Windows side.
> Add new CMS GC flags to cassandra_env.sh for JVM later than 1.7.0_60
> --------------------------------------------------------------------
>
> Key: CASSANDRA-7432
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7432
> Project: Cassandra
> Issue Type: Improvement
> Components: Packaging
> Reporter: graham sanderson
> Assignee: Brandon Williams
> Fix For: 2.0.10, 2.1.1
>
> Attachments: 7432.txt
>
>
> The new flags in question are as follows:
> {code}
> -XX:+CMSParallelInitialMarkEnabled
> -XX:+CMSEdenChunksRecordAlways
> {code}
> Given we already have
> {code}
> JVM_OPTS="$JVM_OPTS -XX:+UseParNewGC"
> JVM_OPTS="$JVM_OPTS -XX:+UseConcMarkSweepGC"
> JVM_OPTS="$JVM_OPTS -XX:+CMSParallelRemarkEnabled"
> JVM_OPTS="$JVM_OPTS -XX:+UseTLAB"
> if [ "$JVM_ARCH" = "64-Bit" ] ; then
> JVM_OPTS="$JVM_OPTS -XX:+UseCondCardMark"
> fi
> {code}
> The assumption would be that people are at least running on large number CPU
> cores/threads
> I would therefore recommend defaulting these flags if available - the only
> two possible downsides for {{+CMSEdenChunksRecordAlways}}:
> 1) There is a new very short (probably un-contended) lock in the "slow" (non
> TLAB) eden allocation path with {{+CMSEdenChunksRecordAlways}}. I haven't
> detected this timing wise - this is the "slow" path after all
> 2) If you are running with {{-XX:-UseCMSCompactAtFullCollection}} (not the
> default) *and* you call {{System.gc()}} then {{+CMSEdenChunksRecordAlways}}
> will expose you to a possible seg fault: (see
> [http://bugs.java.com/bugdatabase/view_bug.do?bug_id=8021809])
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