[albntomat0]

There’s a section of the article at the end about how Postgres doesn’t have LTO enabled by default. I’m assuming they’re not doing PGO/FDO either?

From the Bolt paper: “For the GCC and Clang compilers, our evaluation shows that BOLT speeds up their binaries by up to 20.4% on top of FDO and LTO, and up to 52.1% if the binaries are built without FDO and LTO.”

[touisteur]

I've always wondered how people actually get the profiles for Profile-Guided-Optimization. Unit tests probably won't actuate high-performance paths. You'd need a set of performance-stress tests. Is there a write-up on how everyone does it in the wild ?

[mhh__]

You might be surprised how much speedup you can get from (say) just running a test suite as PGO samples. If I had to guess this is probably because compilers spend a lot of time optimising cold paths which they otherwise would have no information about

[its_bbq]

If I remember correctly, at Google we would run a sampling profiler on some processes in prod to create these profiles, with some mechanism for additional manual overrides

[tdullien]

Google and Meta do in-production profiling. I think that tech is coming to everyone else slowly.

[pgaddict]

With the LTO, I think it's more complicated - it depends on the packagers / distributions, and e.g. on Ubuntu we apparently get -flto for years.