`tsgo` slow - too much type and type instantiation without `--singleThreaded` options

[noelkim-prestolabs]

If i tried tsgo --diagnostics,

Files:                    5963
Lines:                  957886
Identifiers:            838616
Symbols:               2581005
Types:                 1587849
Instantiations:        6891764
Memory used:          2147995K
Memory allocs:        27727625
Config time:            0.129s
BuildInfo read time:    0.000s
Parse time:             0.400s
Bind time:              0.000s
Check time:            40.192s
Emit time:              0.076s
Changes compute time:   0.115s
Total time:            40.916s

and i tried with --singleThreaded,

Files:                    5963
Lines:                  957886
Identifiers:            838616
Symbols:               1544239
Types:                  679899
Instantiations:        2537315
Memory used:          1367003K
Memory allocs:        16330303
Config time:            0.132s
BuildInfo read time:    0.000s
Parse time:             2.240s
Bind time:              0.000s
Check time:            14.294s
Emit time:              0.076s
Changes compute time:   0.220s
Total time:            16.964s

and i tried with tsc --diagnostics,

Files:              5963
Lines:            957884
Identifiers:      844220
Symbols:         1501749
Types:            536783
Instantiations:  2232432
Memory used:    1993608K
I/O read:          1.26s
I/O write:         0.00s
Parse time:        4.36s
Bind time:         0.57s
Check time:       23.92s
Emit time:         0.05s
Total time:       28.90s

tsgo version: 7.0.0-dev.20260107.1
Hardware:

Hardware Overview:

  Model Name: MacBook Pro
  Model Identifier: Mac15,7
  Chip: Apple M3 Pro
  Total Number of Cores: 12 (6 performance and 6 efficiency)
  Memory: 36 GB

pprof for default tsgo

51524-cpuprofile.pb.gz

51524-memprofile.pb.gz

pprof for --singleThreaded tsgo

52264-cpuprofile.pb.gz

52264-memprofile.pb.gz

[ahejlsberg]

Any chance you can share a repro with us? It's practically impossible to diagnose the situation without one.

[DanielRosenwasser]

Just as a heads up, you can (currently) use --checkers 1 instead of --singleThreaded to get parallel parse/emit, but single-threaded checking.

[jakebailey]

Looking at the profile:

Some of this is fixable (the growslice, I will send a PR), but a lot of time is spent adding things to a union.

I would suggest trying to run tsc with --generateTrace to find the giant union: https://github.com/microsoft/TypeScript/wiki/Performance-Tracing

Or maybe even https://www.npmjs.com/package/typeslayer.

The best case scenario is to have the repro, so we can test things, though.

[ahejlsberg]

Summarizing our discussion about this issue: It appears there's a file with some very expensive union types that is referenced (directly or indirectly) by most other files in the program. This file is part of file set for each of the multiple checkers we create when checking concurrently, and therefore the expensive work is performed multiple times. We can look at speeding up union type construction, but the best remedy would obviously be to not have the expensive union types in the first place.

[noelkim-prestolabs]

@DanielRosenwasser Here's result of --checkers 1.

Files:                    5963
Lines:                  957886
Identifiers:            838616
Symbols:               1544239
Types:                  679899
Instantiations:        2537315
Memory used:          1372899K
Memory allocs:        16529251
Config time:            0.127s
BuildInfo read time:    0.000s
Parse time:             0.412s
Bind time:              0.001s
Check time:            14.252s
Emit time:              0.069s
Changes compute time:   0.124s
Total time:            14.989s

83209-cpuprofile.pb.gz
83209-memprofile.pb.gz

and I think "very expensive union types" is our type for suggesting translation ids in tsx component, that extracted from large json file.
maybe I can bring that repro if #2458 cannot resolve this issue.

[jakebailey]

My linked PR definitely will not "solve" your issue, just improve it by a bit.

Not sure you really want to upload those files, given it contains paths and type names from your private project.

[noelkim-prestolabs]

I understand, I'll prepare the repro If i can

[noelkim-prestolabs]

repro prepared.

https://github.com/noelkim-prestolabs/tsgo-repro