Can startup time be improved to be on par with other languages?

[hlandau]

I'd like to get into Racket as a Scheme user, but its high startup times are a blocker for me:

$ time racket -e '(display "hello")'
hello
real 0m0.721s
user 0m0.598s
sys 0m0.119s

This basically rules out using it for command line scripts, which is a major class of uses for me.

Some have suggested using #lang racket/base and raco make to reduce the time. This reduces execution time to 0.175s. However this is still worse than Python and Guile, which manage 0.033s and 0.022s respectively, neither of which need a precompile step (which would make this kind of usage impractical).

Could this be improved in a future Racket?

[mfelleisen]

Rash? https://docs.racket-lang.org/rash/

[soegaard]

Could this be improved in a future Racket?

It's a problem we are aware of, but the low-hanging fruit have been picked.

On my laptop from 2019 the numbers are:

0.48s user
0.22s system 67% cpu
1.042 total

I expect newer systems to be faster.

Note that the startup time will be neglible when the script actually has work to do.

If you find the problem large enough, a potential solution, you could explore:

• make a racketd that runs in the background
• let your script invoke racketd.

This solution is/was used by Emacs:
https://www.emacswiki.org/emacs/EmacsAsDaemon

Would it be ok to close this again?

[mflatt]

One of the obstacles to a fast startup time in Racket is that a lot of things are expected to be available in all contexts, like eval or individual modules that are part of the racket/base module. We may be able to reset those expectations and guarantees so that a rhombus executable can start faster, but it's an open problem at this point.

[LiberalArtist]

I'd like to get into Racket as a Scheme user, but its high startup times are a blocker for me:

$ time racket -e '(display "hello")' hello real 0m0.721s user 0m0.598s sys 0m0.119s

This basically rules out using it for command line scripts, which is a major class of uses for me.

Some have suggested using #lang racket/base and raco make to reduce the time. This reduces execution time to 0.175s. However this is still worse than Python and Guile, which manage 0.033s and 0.022s respectively, neither of which need a precompile step (which would make this kind of usage impractical).

Could this be improved in a future Racket?

One difference to note when running code from a file is that Guile has auto-compilation enabled by default, which is equivalent to using the new-ish -y/--make flag to racket. You can put this in a shebang line with #!/usr/bin/env -S racket -y or similar.

More broadly, the Guile developers have put particular effort into startup time, and it has paid off. Nonetheless, many of us do write scripts in Racket!

I was surprised when I tried this that passing a program with -e took almost three times as long as running it from a (module) file, though:

philip@bastet:/tmp/times$ time racket -e '(display "hello")'
hello
real    0m0.231s
user    0m0.171s
sys     0m0.060s
hellophilip@bastet:/tmp/times$ echo '#lang racket/base (displayln "hello")' >hi.rkt
philip@bastet:/tmp/times$ time racket hi.rkt 
hello

real    0m0.079s
user    0m0.047s
sys     0m0.031s
philip@bastet:/tmp/times$ time racket -y hi.rkt 
hello

real    0m0.122s
user    0m0.073s
sys     0m0.035s
philip@bastet:/tmp/times$ time racket -y hi.rkt 
hello

real    0m0.097s
user    0m0.076s
sys     0m0.021s
philip@bastet:/tmp/times$ time racket hi.rkt 
hello

real    0m0.065s
user    0m0.041s
sys     0m0.024s
philip@bastet:/tmp/times$ time guile -c '(display "hello")'
hello
real    0m0.011s
user    0m0.006s
sys     0m0.006s
philip@bastet:/tmp/times$ echo '(display "hello")(newline)' >hi.scm
philip@bastet:/tmp/times$ time guile --no-auto-compile hi.scm 
hello

real    0m0.016s
user    0m0.009s
sys     0m0.009s
philip@bastet:/tmp/times$ time guile hi.scm 
;;; note: auto-compilation is enabled, set GUILE_AUTO_COMPILE=0
;;;       or pass the --no-auto-compile argument to disable.
;;; compiling /tmp/times/hi.scm
;;; compiled /home/philip/.cache/guile/ccache/3.0-LE-8-4.6/tmp/times/hi.scm.go
hello

real    0m0.035s
user    0m0.030s
sys     0m0.024s
philip@bastet:/tmp/times$ time guile hi.scm 
hello

real    0m0.011s
user    0m0.009s
sys     0m0.005s

(My /tmp is a tmpfs, and I ran the initial command a few times to make sure the filesystem cache was hot.)