memory management - Mem usage is different from TOP and JMAP for java application -


it's reducer program in hadoop job. "top" command tells me res 4.0g mem, , data 4.5g. , system begins use swap. run reducer -xmx4g option.

in same time, use jmap see histogram of objects

 jmap -histo pid

and tells me in total things in heap sum 1.3g mem. repeated several times , result same. why such big difference between top , jmap, remaining memory?

i use sun java 7 , in program there's lots of int[] (allocated new).

thanks.


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