String interning

[marselester]

Have you already considered string interning to reduce memory consumption?

I am aware of several approaches:

• map[string]string cons: it could grow forever
• https://github.com/go4org/intern cons: doesn't support []byte slices, see Is it possible to reduce allocations when interning a byte slice? go4org/intern#18

It looks like Thanos got good results with go4org/intern thanos-io/thanos#5926, though I am not sure if it's ok to intern like that intern.GetByString(s).Get().(string) go4org/intern#19.

See also Optimizing string usage in Go programs slides.

[metalmatze]

While we can certainly work towards improving the usage of strings, I don't see it being the highest contender for further improvements in Parca itself right now: https://pprof.me/a2522ef
Having said that, if someone wants to work on this, I don't think anyone is going to be opposed to merging those changes!

[marselester]

Sounds good! It would be better to compare a memory footprint (resident set size) with and without string interning (i.e., storing only one copy of a string) on production where Parca receives lots of duplicate strings (labels, symbols). From what I understand, we won't see any difference in a heap profile; at least I didn't see a difference in benchmarks, but RSS and the size of structs that held interned strings were smaller (measured with github.com/DmitriyVTitov/size).

[kakkoyun]

There are some discussions on adding a package to stdlib golang/go#62483