Forum OpenACS Q&A: Response to Server Load Question...

Posted by James Thornton on
If you do a search on Google for "uptime unix load average," then you will find

Here's an excerpt (is it inaccurate?)...

Load Average

On a single processor machine, a load of 1 is maximum efficient utilization. Loads more than the number of processors mean the machine is too heavily loaded. Any load numbers in the 2 or 3 range is an indication of excessive CPU use and consequently poor performance. Load average numbers should be in the decimal range, for example; .02 or .53. 

Load average is the amount of load that the server's CPU is experiencing. What creates load on a CPU? When a program is run i.e., a search program, a shopping cart program, a request to upload a web site's page to a browser, an email program etc.. When any of the preceding scenarios occur, a load (or demand) is placed on the server's CPU. Some processes are given a higher priority by the CPU i.e., if a server is performing a search and a visiting web surfer happens to request a web page from a site hosted on that same server, then the page upload is given priority over the search. The search will slow down in order to accommodate the page upload.

Relative to page uploads the CPU's load average is not as critical as the pipeline to server. The pipeline is the connection from the server to the backbone provider. Pipelines are designated as 0C3, DS3, T3, T1, etc.. and are an indication of how much data can be transmitted in kilo bytes per second. A heavily loaded CPU will usually be able to out perform the pipeline.

The load average numbers of 0.28, 0.18, 0.22 are reflections of 1, 5 and 15 minute intervals respectively.

Numbers like this "3.30, 1.05, 0.96" are not as much a cause for alarm as numbers like this "2.52, 2.56, 2.51". The second set of numbers show consistent heavy demand on the processor. This consistent heavy load will deny the web pages the priority they need to load quickly. The first set of numbers is indicative of a single process or program (such as a search) performing it's function and will likely end very soon.