I have a CentOS 7 server that is running out of memory and I can't figure out why.
Running "free -h" gives me this: total used free shared buff/cache available Mem: 3.4G 2.4G 123M 5.9M 928M 626M Swap: 1.9G 294M 1.6G
The problem is that I can't find 2.4G of usage. If I look at resident memory usage using "top", the top 5 processes are using a total of 390M. The next highest process is using 8M. For simplicity, if I assume the other 168 processes are all using 8M (which is WAY too high), that still only gives a total of 1.7G. The tmpfs filesystems are only using 18M, so that shouldn't be an issue.
Yesterday, the available memory was down around 300M when I checked it. After checking some things and stopping all of the major processes, available memory was still low. I gave up and rebooted the machine, which brought available memory back up to 2.8G with everything running.
How can I track what is using the memory when the usage doesn't show up in top?