Everything You Know About Latency Is Wrong

Everything You Know About Latency Is Wrong by Tyler Treat.

From the post:

Okay, maybe not everything you know about latency is wrong. But now that I have your attention, we can talk about why the tools and methodologies you use to measure and reason about latency are likely horribly flawed. In fact, they’re not just flawed, they’re probably lying to your face.

When I went to Strange Loop in September, I attended a workshop called “Understanding Latency and Application Responsiveness” by Gil Tene. Gil is the CTO of Azul Systems, which is most renowned for its C4 pauseless garbage collector and associated Zing Java runtime. While the workshop was four and a half hours long, Gil also gave a 40-minute talk called “How NOT to Measure Latency” which was basically an abbreviated, less interactive version of the workshop. If you ever get the opportunity to see Gil speak or attend his workshop, I recommend you do. At the very least, do yourself a favor and watch one of his recorded talks or find his slide decks online.

The remainder of this post is primarily a summarization of that talk. You may not get anything out of it that you wouldn’t get out of the talk, but I think it can be helpful to absorb some of these ideas in written form. Plus, for my own benefit, writing about them helps solidify it in my head.

Great post, not only for the discussion of latency but for two extensions to the admonition (Moon is a Harsh Mistress) “Always cut cards:”

  • Always understand the nature of your data.
  • Always understand the nature your methodology.

If you fail at either of those, the results presented to you or that you present to others may or may not be true, false or irrelevant.

Treat’s post is just one example in a vast sea of data and methodologies which are just as misleading if not more so.

If you need motivation to put in the work, how’s your comfort level with being embarrassed in public? Like someone demonstrating your numbers are BS.

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