[
https://issues.apache.org/jira/browse/CASSANDRA-20745?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18010619#comment-18010619
]
Michael Semb Wever commented on CASSANDRA-20745:
------------------------------------------------
bq. CMS GC is deprecated in Java 9 and removed in Java 14. So, in Cassandra 5.0
and especially in trunk we should not use it.
We shouldn't remove it in 5.0
Folk are still using CMS actively, and reporting that it still performs better
than G1 with heaps <=16GB.
Removing it from trunk, especially as we prepare for removing support for
jdk11, should be a separate ML thread.
> nodetool not started when MAX_HEAP_SIZE is set only in cassandra-env.sh
> -----------------------------------------------------------------------
>
> Key: CASSANDRA-20745
> URL: https://issues.apache.org/jira/browse/CASSANDRA-20745
> Project: Apache Cassandra
> Issue Type: Bug
> Components: Legacy/Tools
> Reporter: Stefan Miklosovic
> Assignee: Stefan Miklosovic
> Priority: Normal
> Fix For: 5.0.x, 5.x
>
> Time Spent: 3h 20m
> Remaining Estimate: 0h
>
> cassandra-env.sh says in its documentation this (1)
> {noformat}
> # Override these to set the amount of memory to allocate to the JVM at
> # start-up. For production use you may wish to adjust this for your
> # environment. MAX_HEAP_SIZE is the total amount of memory dedicated
> # to the Java heap. HEAP_NEWSIZE refers to the size of the young
> # generation when CMS is used.
> #
> # When using G1 only MAX_HEAP_SIZE may be set, and HEAP_NEWSIZE must be
> # left unset.
> #
> # When using CMS both MAX_HEAP_SIZE and HEAP_NEWSIZE should be either set
> # or not (if you set one, set the other).
> #MAX_HEAP_SIZE="20G"
> #HEAP_NEWSIZE="10G"
> #MAX_DIRECT_MEMORY_SIZE="10G"
> {noformat}
> Okay, so when I am going to use G1 then I need to set MAX_HEAP_SIZE only and
> I have to leave HEAP_NEWSIZE unset.
> So I do that, by uncommenting only that line:
> {code}
> MAX_HEAP_SIZE="20G"
> #HEAP_NEWSIZE="10G"
> #MAX_DIRECT_MEMORY_SIZE="10G"
> {code}
> Then Cassandra starts and I am going to invoke nodetool:
> {code}
> $ nodetool status
> please set or unset MAX_HEAP_SIZE and HEAP_NEWSIZE in pairs when using CMS GC
> (see cassandra-env.sh)
> {code}
> The reason this is happening is that nodetool adds all parameters from
> jvm(11|17)-clients.options which do not contain any information about GC:
> {code}
> -Djdk.attach.allowAttachSelf=true --add-exports
> java.base/jdk.internal.misc=ALL-UNNAMED --add-exports
> java.base/jdk.internal.ref=ALL-UNNAMED --add-exports
> java.base/sun.nio.ch=ALL-UNNAMED --add-exports
> java.management.rmi/com.sun.jmx.remote.internal.rmi=ALL-UNNAMED --add-exports
> java.rmi/sun.rmi.registry=ALL-UNNAMED --add-exports
> java.rmi/sun.rmi.server=ALL-UNNAMED --add-exports
> java.sql/java.sql=ALL-UNNAMED --add-opens
> java.base/java.lang.module=ALL-UNNAMED --add-opens
> java.base/jdk.internal.loader=ALL-UNNAMED --add-opens
> java.base/jdk.internal.ref=ALL-UNNAMED --add-opens
> java.base/jdk.internal.reflect=ALL-UNNAMED --add-opens
> java.base/jdk.internal.math=ALL-UNNAMED --add-opens
> java.base/jdk.internal.module=ALL-UNNAMED --add-opens
> java.base/jdk.internal.util.jar=ALL-UNNAMED --add-opens
> jdk.management/com.sun.management.internal=ALL-UNNAMED --add-opens
> java.base/java.lang.reflect=ALL-UNNAMED
> {code}
> However, nodetool eventually sources cassandra-env.sh (2) which will trigger
> that logic.
> More to it, this code in particular seems to be not entirely correct, there
> is a small logical error in that (3).
> {code}
> if [ "x$MAX_HEAP_SIZE" = "x" ] && [ "x$HEAP_NEWSIZE" = "x" -o $USING_G1 -eq 0
> ]; then
> MAX_HEAP_SIZE="$CALCULATED_MAX_HEAP_SIZE"
> HEAP_NEWSIZE="$CALCULATED_CMS_HEAP_NEWSIZE"
> elif [ "x$MAX_HEAP_SIZE" = "x" ] || [ "x$HEAP_NEWSIZE" = "x" -a $USING_G1
> -ne 0 ]; then
> echo "please set or unset MAX_HEAP_SIZE and HEAP_NEWSIZE in pairs when
> using CMS GC (see cassandra-env.sh)"
> exit 1
> fi
> {code}
> When I set MAX_HEAP_SIZE only, as advised on using G1 GC, then "elif" brach
> will go to evaluate
> {code}
> [ "x$HEAP_NEWSIZE" = "x" -a $USING_G1 -ne 0 ]
> {code}
> "xHEAP_NEWSIZE" = "x" will evaluate to true and USING_G1 -ne 0 will evaluate
> to true as well! Why? Because nodetool options do not contain "+UseG1GC"
> so when nodetool calls this
> {code}
> echo $JVM_OPTS | grep -q +UseG1GC
> USING_G1=$?
> {code}
> then USING_G1 will be set to 1, because $? will be 1 as grep returns 1 when
> not found. That evaluates USING_G1 -ne 0 to "true", which makes "[
> "x$HEAP_NEWSIZE" = "x" -a $USING_G1 -ne 0 ]" to be true, which will print
> that error message and nodetool will not start.
> (1)
> https://github.com/apache/cassandra/blob/trunk/conf/cassandra-env.sh#L99-L137
> (2) https://github.com/apache/cassandra/blob/trunk/bin/nodetool#L46-L53
> (3)
> https://github.com/apache/cassandra/blob/trunk/conf/cassandra-env.sh#L131-L137
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org
For additional commands, e-mail: commits-h...@cassandra.apache.org
