Why my java heapSize > rss ? in k8s pods environment

Question

here is the situation about jstat: 3G young,1.7G old,total about 4.7G:

but,in rss situtation,it looks like that:

I don't know why. especially in others pods(with the same container in it), rss > java heapSize.

here is the jvm optition:

-XX:+UseG1GC, 
-XX:+UseStringDeduplication, 
-XX:-OmitStackTraceInFastThrow, 
-XX:MaxRAMPercentage=75.0,
-XX:InitialRAMPercentage=75.0, 
-XX:+PrintTenuringDistribution, 
-XX:+PrintGCDetails, 
-XX:+PrintCommandLineFlags, 
-XX:+PrintHeapAtGC, 
-XX:+PrintGCDateStamps, 
-XX:+PrintGCTimeStamps, 
-Xloggc:log/gc-%t.log,

here is the pod yml:

 resources:
      limits:
        cpu: "4"
        memory: 6Gi
      requests:
        cpu: "1"
        memory: 6Gi