In a previous blog post, I pointed out that such a "knee" is actually an optical illusion. Nonetheless, this same question arose in last month's CMG MeasureIT, as a kind of survey entitled "Does the Knee in a Queuing Curve Exist or is it just a Myth?" Although that author concludes (correctly) that the existence of a "knee" (as it is usually meant) is bogus, the panoply of responses was quite astounding—especially coming from professionals who ought to know better. In this month's MeasureIT, I examine the same question in a rigorous but unconventional way under the title "Mind Your Knees and Queues: Responding to Hyperbole with Hyperbolæ."
Tuesday, August 18, 2009
Response Time Knees and Queues
How do you determine where the response-time "knee" occurs? This is a question one commonly hears with reference to characterizing the performance of an application. Calculating where the response time suddenly begins to climb dramatically is considered, by many, to be an important determinant for such things as load testing, scalability analysis, and setting application service targets.