I have a server running Red Hat Enterprise Linux Server release 6.7. The server runs a number of java processes including a tomcat server with nginx webserver. The server has 12 GB of ram allocated to it.

Upon immediate startup the server shows to be using 1289 MB of ram (free -m -/+ buffers/cache line)... output below.

A "ps aux" on server startup shows the memory usage of all processes being a total of 1,290,996 k of memory (The RSS column)... The 2 numbers are pretty close.

After 2 days of uptime free -m now shows us using 10,698 MB of memory while "ps aux" totals up to 8,345,352 k for all processes.

We've attempted to stop/kill each process one by one and even with an absolute bare minimum number of things running (No Tomcat, no Java, no Nginx) we never recover the "Missing" ~2GB of ram.. The only thing we've found to recover the missing memory is to reboot the server. If the server goes more than 3-4 days without a reboot it starts eating into swap space which eventually causes high CPU usage and the java applications running on it to crawl to a standstill.

I should also mention that this server is running as a virtual machine using VMWare.

Free -m output on startup:

             total       used       free     shared    buffers     cached
Mem:         11852       1787      10064          0         28        468
-/+ buffers/cache:       1289      10562 
Swap:         8191          0       8191 

Free -m output after 2 days uptime

             total       used       free     shared    buffers     cached
Mem:         11852      11625        226          0        146        779
-/+ buffers/cache:      10698       1153 
Swap:         8191         43       8148 

What can I do to help diagnose where the "Missing" memory goes to so that I can resolve the issue. Any suggestions are appreciated.


  • How did you total the output of ps aux? Do you have a tmpfs or ramfs mounted somewhere? Perhaps on /tmp? – muru Dec 23 '15 at 18:53
  • I just dumped it into a file and imported that into excel and totaled the column.. very low-tech We do use tmpfs on the server – jrlambs Dec 23 '15 at 19:00

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