Some Reasons to Measure

Measuring is undervalued, particularly vs writing, because it doesn't show off creativity.

> Measuring is undervalued

Goodhart's law has been a problem with measures.

“When a measure becomes a target, it ceases to be a good measure.”

The problem is that a competitive measure tends to overshadow the utility of the measure (look at anything that starts with a TPC- or the first rotation of a Tesla roadster tire).

So the biggest impact of a measure is immediately after it is introduced, because the market hasn't engineering itself to overfit to that measure.

And that is what Dan's post clearly says, that immediately after he brings up something, there is an actual change in the industry practice that happens.

> it doesn't show off creativity.

But something like Jepsen is amazingly useful because it is a creative nothing-up-my-sleeves end-run around first-party testing - actual third party testing for the product is the red-team to a QE team doing the blue-team work. The problem is that a lot of people leave that to the same vendor who is selling the product with its promises from their sales team - it is hardly an open book into the bugs open list (I work in open-source, so I have to wash my dirty laundry in public).

As a side not to this, I had a meeting in the last 2 days where someone told me that the "QE team is doing a good job, because the test have been consistently green as the release approaches".

And I didn't know exactly how to respond to that.

Looks like he wasn't kidding, at least for Java shops with untuned JVMs. This was linked from the article and from Dan Luu's work at Twitter. "We spent one day1 building a system that immediately found a mid 7 figure optimization (which ended up shipping). In the first year, we shipped mid 8 figures per year worth of cost savings as a result. The key feature this system introduces is the ability to query metrics data across all hosts and all services and over any period of time (since inception), so we've called it LongTermMetrics (LTM) internally since I like boring, descriptive, names.

https://danluu.com/metrics-analytics/

I'll add that I worked in systems at a large php shop which didn't have good metrics for utilization. After the adoption of HHVM their utilization dropped enough that they ended up buying extra hardware in the 6 figures. They knew that performance was a lot better but they didn't quantify it. So surprise! All it took to figure that out and start making better decisions was to collect SAR data and dump it to a central log. So, yeah. Boring is good or at least a good place to start.

Talking about measuring time I would put a date on the blog post

damn, that’s a lot of interesting content. I meant to go to sleep an hour ago, and I’m still reading.