enhance(svg-tester): capture performance data

[marcelgerber]

So, I was curious about performance metrics of grapher, both loading time and memory usage.

To get an overview, I adapted the SVG Tester with some readouts for time taken and memory usage, and these will then be dumped into the results.csv file.

This is easy to do for time taken for rendering, but what's a bit more tricky is getting an accurate readout of the memory consumption (heap used).
To do this in a somewhat good way, I added a (kind of hacky) --isolate mode that will run all the exports sequentially, and runs each in a fresh process. This takes an awfully long time, but it is actually accurate.

If you're curious about the results we get out of this, the results on my machine I put into a Google Sheet here: https://docs.google.com/spreadsheets/d/1Wzz76EYyOT0vo6uqQVMvvAQh0tOJyxcyJuUFfowpzbA/edit?usp=sharing

[ikesau]

Super interesting! I recognize a few of those top slugs as the ones my local bake was freezing on just now when I was testing lightning deploys.

Nice to get some benchmarks on this. Excited to see if we can find any optimizations here.

[danyx23]

Very nice work. I'd be almost tempted to throw all the big covid scatter plots out - I doubt that they are still useful for anyone.

Maybe a good topic for Grapher hour after we meet?

[danyx23]

Let's merge this. In the future we could think of setting up an analytics datasette instance so that we have an easy place where we can write perf results like this to and generate charts from, but that is all downstream from this change.