[adamors]

I benchmarked a good sized app (ran a black-box QA suite multiple times) while monitoring performance and req/response times with Prometheus/Grafana with Ruby 3.2.

With YJIT enabled memory usage ballooned and performance dipped below non-YJIT Ruby 3.2, IIRC the difference was a good 10% degradation. Granted, it's an API only service so no HTML is being generated, only JSON and that could be the culprit.

Suffice it to say, we didn't enable YJIT for 3.2. Maybe 3.3 is indeed different, but both the faster and less memory claims are really suspicious to me.

[apstats]

Interesting. Do you think html generation is one of the things that makes the numbers look so good for 3.2 YJIT? We run a mostly json api only app. I think json serialization is notoriously slow in ruby so I was hoping yjit would speed it up.

[byroot]

YJIT won't help JSON generation because it's all implemented in C (either the stdlib `json`, or `oj` or `yajl` etc.

If what is slow is some RUby code like Active Model Serializers etc, then maybe it can help a bit there.

But yes, generally YJIT works very well on HTML templates because they are compiled as large methods with not a lot of branches.