Saturday, September 20, 2014

RedHat 6 VM with 8 GB RAM - who uses the memory?







after freshly rebooting the VM "top" indicates about 0.5 GB out of 8 GB RAM are being used.
Then we run some installation code. After the install program is done and all subprocesses are terminated, "top" still shows around 5 GB being used, e.g.




Mem: 8062088k total, 5021456k used, 3040632k free, 187892k buffers



Later on, when running the installed software we run into OutOfMemoryErrors even for small Java programs being started. This behaviour did not really change/become better when upgrading the VM from 4 GB to 6 GB and to 8 GB.



Is there a way / a tool




  • to find out what is this memory being used for?

  • to find out how can the memory be released?

  • how can that memory usage probably for operating system usage (rather than user processes) be limited?




Many thanks for any hint,
Uli

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