A process is an instance of a running program.  For example, when someone requests a page from the website, one of the several running Apache processes gets the file from the disk and sends it to the user.  If Apache detects the current processes are too busy to keep up with user demand, it will start more processes to help out.  Other programs behave similarly.  So, the number of processes is an indication of how busy your CPU is.  Of course, running programs need memory to continue to exist, so each one that is running consumes some memory.  You can limit the maximum number of processes that start if you need to.

A TCP socket is a network connection.  The HTTP protocol used TCP as its underlying network transport protocol.  Each person who wants to communicate with the web site (in order to download a file, for example,) creates a TCP connection to your server.  The connection will stay open for a short time in case the same person wants to use it some more.  After a period of inactivity, the connection will close, freeing the socket.  Network sockets and network ports are similar ideas.  So, the number of open TCP sockets give you an idea of how many computers are communicating with your server via the network.

Here's a for our memory usage: 334 MB. Our current web hosting plan provides 256 MB RAM, plus an upgrade for an additional 128 MB. So our MAX limit is 384 MB, at which point we would have to upgrade to a more expensive plan.

http://www.wiredtree.com/managedvps/

So we are 50 MB from our limit.



This daily graphs appears fairly constant and level. Fluctuations based on earlier usage-graphs however, are something I find interesting. I mean, our memory usage has been down below 200 (tho barely) .. while now it's well over 300. That's a sizable fluctuation.

Our memory limit of 384 MB now looms not-so-far away. After dealing with Lunarpages these last 3 months (trying to reduce our usage of server resources) I am sensitive to all server-based limits .. which now seem to focus on our use of memory.

The question now seems to be > at what point do we start to get concerned about memory usage? 50 MB does not seem like very much of a safety buffer. 334 is 87% of our 384 limit. Certainly, 95% usage would require looking into increasing our current memory limit (which would mean paying higher monthly hosting fees).

95% of our 384 MB limit = 365 .. or about 30 MB more .. which makes me reluctant to install Drupal 6 (Content Management System): http://drupal.org/about

.. or at least hesitant. $7.50/month would buy us an additional 64 MB memory. So it's not something we can't afford. (3 less expresso's per month for me.)

Rad wrote on Mar 8^th, 2008 at 8:35am:

It depends on the timeout value for each.  YaBB might consider someone as being here if they've requested a page in the last 10 minutes, for example.  TCP connections, on the other hand, remain open for as little as a few seconds, so some of the people YaBB considers here may not have an open TCP connection.

If your definition of 'instant' corresponds to how long your server holds tcp connections open (usually anywhere from a few seconds to a few minutes,) then that is an accurate statement.

TCP Sockets peak at 134. Interesting. Wonder why.



This thread on search engines visiting here is loosely related to this post on TCP Sockets:

http://radified.com/cgi-bin/yabb2/YaBB.pl?num=1207513715

We exceeded our allowable memory limit (for the first time), which I mentioned in a separate post, found here:

http://radified.com/cgi-bin/yabb2/YaBB.pl?num=1208353800