Queues in the News

You might not have noticed, but queues have been in the news a lot lately. Not from the standpoint of computer performance but people performance or more accurately, crowd control. Most recently, queues popped up in the context of long delays expected at Heathrow airport due to big crowd arrivals for the London Olympics.

• Fears over Heathrow queues during Olympics
• The Waiting Game by The Numbers Guy
• QANTAS to Get No Queues

In a queue, at least everyone is pointing in the same logical direction. Moreover, if you snake the queue, as they do at Disneyland, people always feel close to the destination and can see it getting even closer as customers ahead of them are processed. That helps to minimize their level of frustration: the control part. For some reason, the post office hasn't figured this out yet.

And, last but not least, queues and computer performance still remain an inevitable perennial. Most recently having to do with the Internet.

Load Testing with Uniform vs. Exponential Arrivals

In a couple of recent blog posts about generating exponential loads and why that is important for load testing and performance testing, it was not completely clear to some readers what was motivating my remarks. In this post, I will try to provide a more visual elaboration of that aspect.

My fundamental point is this. When it comes to load testing^*, presumably the idea is to exercise the system under test (SUT). Otherwise, why are you doing it? Part of exercising the SUT is to produce significant fluctuations in the number of requests residing in application buffers. Those fluctuations can be induced by the pattern of arriving requests issued by the client-side driver (DVR): usually implemented as a pile of PCs or blades.