[azakai]

In general you'd be right, but this is not a benchmark of code running in those languages. There is no loop, no heavy computation - it's just returning the headers. That should take less than 1ms in either language.

Startup time might be a factor. But the measurements of the same language running on the same provider's infrastructure go from around 10 to 50ms (on one provider) and 10 to 100ms (on the other). Those huge differences don't look like CPU latencies (the machines aren't 5x or 10x faster in different locations) - they are likely network latencies. So programming language is probably a very minor factor here (at least in the non-beta services, which is what was measured here - maybe it was an issue in the older measurements).

[technobabbler]

> In general you'd be right, but this is not a benchmark of code running in those languages. There is no loop, no heavy computation - it's just returning the headers. That should take less than 1ms in either language.

They can't have it both ways... Fastly was the one that complained that their JS engine still wasn't up to par (being in beta), so clearly the language of choice (or interpreter/compiler/whatever) DOES matter.

Either the language doesn't matter (in which case, replicate the JS test) or it does, in which case this isn't even a useful comparison.

[azakai]

Sorry, I should have been clearer. The new benchmark data does not look like it is influenced by the language in a noticeable way (since we see 5x or 10x differences in the mean even when using the same language, and which provider is faster or slower depends on which location you measure at).

But it's very possible the old data may have been influenced by the language. That's not very interesting, though: as Fastly said, it's just beta performance. And anyhow this is a benchmark with almost no CPU work anyhow.

[acdha]

I'd also expect unrelated load to be a factor, especially if there's a mechanism which priorities paid customer traffic over the free tier. Given the complexities of loading and running JavaScript, I'd be especially interested in what memory contention looks like — it seems like it could be as simple as Rust needing far less memory than loading all of SpiderMonkey and thus being less likely to hit both low-level CPU cache and high-level runtime cache evictions.

[azakai]

Ah, good point, memory consumption might indeed be a factor here. If that's the case I'd expect higher variance in the measurements perhaps - looking for that in the raw data could be interesting.