I'm a running ubuntu 12.04 LTS server edition and two times in the pasts 48 hours or so the VPS becomes completely unresponsive. Nginx stops responding to requests. There is log activity sent to my logging service. New Relic data stops being sent. I can't even ssh into the box. The only way for me to fix the issue is to go my hosting provider's management system and do a hard restart of the VPS. After the restart everything seems fine until it happens again.
I have 1 GB of RAM plus at least another 1 GB in swap.
I looked though the logs and I have found no evidence of OOM killing any processes.
Below are some screenshots from NewRelic about the server load.
Is there any other place I should look for details? Could be kernel bug.