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https://issues.apache.org/jira/browse/CASSANDRA-15839?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17153193#comment-17153193
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Jeremy Hanna edited comment on CASSANDRA-15839 at 7/8/20, 2:49 AM:
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This is the code that *should* detect whether or not G1 is enabled. However
you can either enable or disable it with {{+UseG1GC}} or {{-UseG1GC}} which are
both matched by that {{grep}}. I have to admit I've never seen anyone in
practice explicitly disable G1.
{code:sh}
echo $JVM_OPTS | grep -q UseG1GC
USING_G1=$?
{code}
That also affects whether we calculate heap sizes automatically or whether we
fail out when we don't set the heap and new size in pairs:
{code:sh}
# only calculate the size if it's not set manually
if [ "x$MAX_HEAP_SIZE" = "x" ] && [ "x$HEAP_NEWSIZE" = "x" -o $USING_G1 -eq 0
]; then
calculate_heap_sizes
elif [ "x$MAX_HEAP_SIZE" = "x" ] || [ "x$HEAP_NEWSIZE" = "x" -a $USING_G1 -ne
0 ]; then
echo "please set or unset MAX_HEAP_SIZE and HEAP_NEWSIZE in pairs when
using CMS GC (see cassandra-env.sh)"
exit 1
fi
{code}
Created CASSANDRA-15931 to address this.
was (Author: jeromatron):
This is the code that *should* detect whether or not G1 is enabled. However
since you can either enable or disable it with that string {{+UseG1GC}} or
{{-UseG1GC}}. I have to admit I've never seen anyone in practice explicitly
disable G1.
{code:sh}
echo $JVM_OPTS | grep -q UseG1GC
USING_G1=$?
{code}
That also affects whether we calculate heap sizes automatically or whether we
fail out when we don't set the heap and new size in pairs:
{code:sh}
# only calculate the size if it's not set manually
if [ "x$MAX_HEAP_SIZE" = "x" ] && [ "x$HEAP_NEWSIZE" = "x" -o $USING_G1 -eq 0
]; then
calculate_heap_sizes
elif [ "x$MAX_HEAP_SIZE" = "x" ] || [ "x$HEAP_NEWSIZE" = "x" -a $USING_G1 -ne
0 ]; then
echo "please set or unset MAX_HEAP_SIZE and HEAP_NEWSIZE in pairs when
using CMS GC (see cassandra-env.sh)"
exit 1
fi
{code}
Created CASSANDRA-15931 to address this.
> Warn or fail to start server when G1 is used and Xmn is set
> -----------------------------------------------------------
>
> Key: CASSANDRA-15839
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15839
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/Startup and Shutdown
> Reporter: Jeremy Hanna
> Assignee: Anthony Grasso
> Priority: Normal
> Fix For: 4.0, 4.0-alpha5
>
>
> In jvm.options, we currently have a comment above where Xmn is set that says
> that you shouldn't set Xmn with G1 GC. That isn't enough - we should either
> warn in the logs or fail startup when they are set together.
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