Bandwidth vs. Latency — The World is Curved

Despite what you may have read in the press lately, neither our world nor the world of performance is flat. This is especially true of the performance metrics commonly known as bandwidth (or throughput) and latency. The performance relationship between these two metrics is curved or nonlinear. In general, this nonlinearity is a consequence of these two metrics being inversely related to each another: increase system throughput to decrease the latency of each request, and vice versa. A common misconception persists, however, that bandwidth and latency are independent performance metrics. I'm going to call that view the Flat-Earth view. Where does that view come from?

Window on the World

In part, it depends on your window to the world. When we look out a window, the Earth looks flat.

Occasionally, we are reminded that the Earth is actually curved. That's something most of us accept and expect, even if we're not aware of it all of the time.

Memcached Scalability at Velocity 2010

Totally stoked about being selected for the Web Performance track at Velocity 2010.


Here's our abstract:

Hidden Scalability Gotchas in Memcached and Friends

Neil Gunther (Performance Dynamics), Shanti Subramanyam (Oracle Corporation), Stefan Parvu (Sun Microsystems)

Most web deployments have standardized on horizontal scaleout in every tier—web, application, caching and database—using cheap, off-the-shelf, white boxes. In this approach, there are no real expectations for vertical scalability of server apps like memcached or the full LAMP stack. But with the potential for highly concurrent scalability offered by newer multicore processors, it is no longer cost-effective to ignore their underutilization due to poor, thread-level, scalability of the web stack. In this session we show you how to quantify scalability with the Universal Scalability Law (USL) by demonstrating its application to actual performance data collected from a memcached benchmark. As a side effect of our technique, you will see how the USL also identifies the most signficant performance tuning opportunities to improve web app scalability.

Human Metro Map and Performance Management

In my Guerrilla classes, I like to compare making a computer performance model (e.g., in PDQ) with model train construction. In the latter case, the goal is to make a scaled replica that includes as much realistism as possible (Aside: I'm assuming this is true, since I have no interest in making model trains). The goal for a performance model is the exact opposite, viz., to throw away as much detail as possible, while still maintaining the essential performance characteristics of the real computer system.

This notion leads to Guerrilla Mantra 2.4:

A performance model is more like a map of a metro rail system than a scaled replica of the metro railway.

Quantum Camera Cited in HP Labs Annual Report

The joint work we published last year on quantum information processing, in New Journal of Physics and Optics Express, has been cited on p. 29 of the 2009 HP Labs Annual Report.

Guerrilla Boot Camps Coming Up

Time to start thinking about getting approval for Guerrilla training in 2010. How to do more with less.


(Click on the image for more details)
Upcoming options:

1. Two-day, entry-level Guerrilla Boot Camp runs Mar 25-26
   
2. Back-2-back Boot Camp and full Guerrilla CaP course runs May 6-14

All Guerrilla classes have a certification level 1, 2, 3, but there are no prerequisites at this time. For those of you coming from international locations, here is a table of currency exchange rates.

We look forward to seeing all of you here!

Guerrilla Mantras Now Updated on Twitter

Those of you in the trenches carrying out performance analysis and capacity planning, perhaps doing it off your own bat, often find yourself in the position where you wish you could point quickly to a more authoritative list of reasons in support your goals. It can mean the difference between convincing your management or not.


To this end, the Guerrilla Manual is provided as a pull-out booklet in the rear jacket of my Guerrilla Capacity Planning book. Now, for an even more rapid-fire response, Guerrilla mantras (140 characters or less) are automatically posted on Twitter. Look for the GMantra tag.

A4 (ain't just paper anymore): Apple's New Chip

In case you missed it, with the advent of the iPad, Apple Inc. has entered the CPU business. While many pundits are still scratching their heads and wondering, "Who needs a giant iPod Touch?" Chris O'Brian notes:

"For the first time, Apple has built it’s own chip for a product. For years, the company has worked with others, first Motorola and then IBM, to build its processors. But for the iPad, the company debuted its A4 chip. The chip came via its acquistion of P.A. Semi in 2008. Building its own chip reportedly was one of the key reasons Apple was able to bring the cost of the iPad down. But early reviewers have also noted the iPad’s speed at rendering Web pages. The A4 potentially puts Apple in a position to build more of its own chips, and it also sets up a new rivalry against Intel for the mobile computing business."

Apple has built chips before; he means home-grown microprocessor.