RAM Usage

Some notes on the RAM allocated and used by the virtual servers as of June 2013, see ticket:555#comment:61 for the reason for the creation of this page and the time spend on it.

puffin

wiki:PuffinServer is the server running ​https://www.transitionnetwork.org/ and it was originally created with 4GB of RAM. On 20th June, following problems related to how it was coping with the load it was under, this was doubled to 8GB of RAM.

Following is a memory usage graph from the Munin stats for the server which illustrate the increase:

Key figures to consider in the above graph is the value for the amount of current committed and active RAM, in this case 8.82GB and 4.63GB and also the amount of maximum committed and active RAM, in this case 4.30GB and 5.12GB.

The sawtooth pattern is caused by MySQL slowly increasing it's memory usage as more things are cached and MySQL restarts, this is made clear in the graph below which tracks the memory used by some of the key processes on the server:

The increase in php-fpm memory usage above, which coincides with the increase in the RAM allocated to the server, is due to an increase in the minimum number of php-fpm processes which are kept available to server client requests.

In the first graph above one key thing to note is the amount the server is swapping -- this is is in red and it's also illustrated on the following graph of swap space used: