s0ulleSS - 2012-02-24

Hi guys.
Have some problem with memory usage statistic.
Sometimes have 502 errors on our project.
When I use command top via ssh it display 4gb of memory and 3.8gb in usage right now. It looks like truth, but webmin display 800mb in usage. Statistic of webmin cant explain why we have 502 error sometimes, so top looks correctly. I know that webmin cant run interactive command like top. So where it take data about memory usage and why we have so big difference between top and webmin.
Thanks in advance for help.