We have an application that is deployed on the tomcat 8 application server, and currently the monitoring server (zabbix) is configured to generate an alert if the heap memory is used at 90%.
There were certain warnings that prompted us to analyze the heap dump. Nothing came out of the heap, there was no memory leak. There were many unreachable objects that were not cleared due to lack of GC.
JVM configurations:
-Xms8192m -Xmx8192m -XX:PermSize=128M -XX:MaxPermSize=256m
-XX:+UseParallelGC -XX:NewRatio=3 -XX:+PrintGCDetails
-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/app/apache-tomcat-8.0.33
-XX:ParallelGCThreads=2
-Xloggc:/app/apache-tomcat-8.0.33/logs/gc.log
-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStamps
-XX:+PrintGCTimeStamps -XX:GCLogFileSize=50m -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=30
We tried to start garbage collection manually using the jcmd command, and it cleared the memory. GC logs after running jcmd:
2016-11-04T03:06:31.751-0400: 1974627.198: [Full GC (System.gc()) [PSYoungGen: 18528K->0K(2049024K)] [ParOldGen: 5750601K->25745K(6291456K)] 5769129K->25745K(8340480K), [Metaspace: 21786K->21592K(1069056K)], 0.1337369 secs] [Times: user=0.19 sys=0.00, real=0.14 secs]
Questions:
- Is there any configuration due to which the GC does not work automatically.
- ? , Java GC, . GC, 90%, ( - , ).