Strange Loop Conference
9 HN recommenders · recommended in 20 months, 2015–2026
42:59 · 119K views · Sep 28, 2015
Gil Tene of Azul Systems explains common pitfalls in measuring latency and response time, including why averages mislead and the problem of coordinated omission. He introduces open source tools like HdrHistogram for better measurement and reporting.
The canonical recommendation whenever percentiles, tail latency, load testing or averages come up, described by some as life changing.
20 comments from Hacker News
This topic always leads me to think about this great talk from Gil Tene on how NOT to measure latencies (basically, don't use averages!). this video I'm also a huge fan of how Dormando showed latency distributions in one of his recent Memcached Extstore posts. The default is 95th percentile but you can change the percentile to what matters to you (i.e. 99th percentile if you ask me!). Scroll down to see what he did and play with it. [LINK]
Doesn't this depend on how "tuned" your subcomponents are? If I had a system that's supposedly heavily optimized, I would simply start seeing the worst-case latency on a higher percentile, 99.9th and so forth. Gil Tene has an excellent talk[1] on this. [1] this video
We use locust at work but I HIGHLY recommend wrk for a very robust yet simple load testing tool. [LINK] And of course, this talk by Gil Tene is fantastic if you're interested in load testing stats this video
This a life changing video by Gil Tene on this topic. Bottom line is because of the number requests to support a single customer "request", the high percentiles are the ones that actually matter. this video
Gil Tene has an entire talk about this point called "How NOT to measure latency" ( this video ). In many circumstances, a web service (either server or client) has large numbers of dependencies, so a user only has to hit 95th-percentile latency for one dependency to have their overall latency significantly hurt. In other words, users may encounter the "rare" bad case on a majority of requests. Thus, even higher percentiles should be tightly controlled in order to truly keep a web service's overall latency under control.