Switching from CMS to G1GC
To move from Concurrent Mark Sweep (CMS) GC to Garbage First (G1) GC, you must update
the HADOOP_NAMENODE_OPTS
settings in
hadoop-env.sh
.
On the Ambari dashboard, select HDFS > Configs >
Advanced > Advanced hadoop-env.
Make the following changes to the
HADOOP_NAMENODE_OPTS
settings:- Replace
-XX:+UseConcMarkSweepGC
with-XX:+UseG1GC
- Remove
-XX:+UseCMSInitiatingOccupancyOnly
and-XX:CMSInitiatingOccupancyFraction=####
- Remove
-XX:NewSize=####
and-XX:MaxNewSize=####
- (Optional) Add
-XX:MaxGCPauseMillis=####
- (Optional) Add
-XX:InitiatingHeapOccupancyPercent=####
- (Optional) Add
-XX:ParallelGCThreads=####
, if not present.The default value of this parameter is set to the number of logical processors (up to a value of 8). For more than eight logical processors, the default value is set to 5/8th the number of logical processors.