rvm.sh performance

[joelmccracken]

I recently tried ribbit, especially the shell version, which is particularly interesting to me (for various reasons I can expound upon if you wish, though given you put the effort in to a shell version, you probably already know them).

However, I found the shell interpreter so slow as to be essentially unsable. Is there some trick that might help that I might be missing? I do imagine it won't be a particularly fast environment in general.

[feeley]

Nice to see even the shell version has fans! Which shell are you using? We have found that ksh gives the best performance. But don't expect miracles! The shell is not known for high-performance computing. But it does have the advantage of very high portability with easy installation and no dependencies.

For example:

$ echo "(define f (lambda (x) (if (> x 0) (+ x (f (- x 1))) 0)))(f 100)" | time ksh prebuilt/repl-max.sh > /dev/null
        2.06 real         2.01 user         0.04 sys
$ echo "(define f (lambda (x) (if (> x 0) (+ x (f (- x 1))) 0)))(f 100)" | time bash prebuilt/repl-max.sh > /dev/null
        4.28 real         4.18 user         0.09 sys
$ echo "(define f (lambda (x) (if (> x 0) (+ x (f (- x 1))) 0)))(f 100)" | time dash prebuilt/repl-max.sh > /dev/null
       16.89 real        16.43 user         0.42 sys
$ echo "(define f (lambda (x) (if (> x 0) (+ x (f (- x 1))) 0)))(f 100)" | time zsh prebuilt/repl-max.sh > /dev/null
       71.62 real        69.75 user         1.42 sys

As you can see there is a 35x difference between the fastest and slowest shell (ksh and zsh).

[feeley]

Moreover, since we wrote the shell version and have worked on the pnut compiler which also uses the shell, we have learned of faster shell idoms. For example the Ribbit shell version makes extensive uses of eval, for example eval x=\$Y$z. It turns out to be faster to avoid eval and do x=$((Y$z)). So maybe the code could be rewritten with that in mind. Something to explore anyway.

[leo-ard]

If you are more interested in the shell version, there is also a fully r4rs complient REPL in shell on the pnut.sh repository: repl.sh (compiled from this c source file : repl.c). This version supports file I/O, call/cc, etc (if you are ready to wait a little bit)

In my experience this version is slow, but faster than my expectation with the right settings. (display "hello") can be shown in under one second. Keep in mind that there is 2 levels of interpretation with this version, which is why I expected slow speeds:

1. A scheme interpreter written in shell (Ribbit RVM)
2. A shell interpreter running the scheme interpreter

[joelmccracken]

So, I'm using bash 3.2 from macos (this is the last version that will be supported by macos, apparently). That's my general target (as its one of the key platforms I care about where such a tool would be interesting to me)

I can try pnut and see how it impacts perf, or see about making tweaks to it for potential better performance.

on macos packaged version of bash:

% echo "(define f (lambda (x) (if (> x 0) (+ x (f (- x 1))) 0)))(f 100)" | time bash prebuilt/repl-max.sh > /dev/null 

bash prebuilt/repl-max.sh > /dev/null  180.37s user 0.83s system 98% cpu 3:03.65 total

TYVM!

[feeley]

It is not normal that it takes 45x longer on your machine! Are you on a super old machine?

[joelmccracken]

I'm on an mac, M1 pro, 16 gig ram. Not the newest/fastest machine, but not that old either

[feeley]

I'm on an mac, M1 pro, 16 gig ram. Not the newest/fastest machine, but not that old either

The numbers I quote above (with bash taking 4.2 seconds for the same execution) were done on an Apple M2, which is just a bit faster than the M1. I suspect something unexpected is causing a slowdown. Can you try the same thing with ksh, dash and zsh? That way we can see if it is your bash that is causing issues. Something that I have noticed in the past is that the size of your shell environment (number of shell variables) can have an influence on the execution time.

[joelmccracken]

joel.mccracken@RL-88478875 src % echo "(define f (lambda (x) (if (> x 0) (+ x (f (- x 1))) 0)))(f 100)" | time /bin/ksh prebuilt/repl-max.sh > /dev/null
/bin/ksh prebuilt/repl-max.sh > /dev/null  2.33s user 0.03s system 97% cpu 2.424 total

joel.mccracken@RL-88478875 src % echo "(define f (lambda (x) (if (> x 0) (+ x (f (- x 1))) 0)))(f 100)" | time /opt/homebrew/bin/bash prebuilt/repl-max.sh > /dev/null
/opt/homebrew/bin/bash prebuilt/repl-max.sh > /dev/null  4.88s user 0.08s system 99% cpu 5.008 total

joel.mccracken@RL-88478875 src % /opt/homebrew/bin/bash --version
GNU bash, version 5.2.37(1)-release (aarch64-apple-darwin24.2.0)

joel.mccracken@RL-88478875 src % echo "(define f (lambda (x) (if (> x 0) (+ x (f (- x 1))) 0)))(f 100)" | time /bin/bash prebuilt/repl-max.sh > /dev/null 
/bin/bash prebuilt/repl-max.sh > /dev/null  183.16s user 0.86s system 99% cpu 3:04.83 total
joel.mccracken@RL-88478875 src % /bin/bash --version                                                                                                     
GNU bash, version 3.2.57(1)-release (arm64-apple-darwin24)
Copyright (C) 2007 Free Software Foundation, Inc.

joel.mccracken@RL-88478875 src % echo "(define f (lambda (x) (if (> x 0) (+ x (f (- x 1))) 0)))(f 100)" | time /bin/dash prebuilt/repl-max.sh > /dev/null
/bin/dash prebuilt/repl-max.sh > /dev/null  19.41s user 0.40s system 99% cpu 19.946 total

I'm having trouble figuring out the versions of ksh and dash. But at least ksh seems to be fast enough to be usable, which makes me ponder writing a shim/loader of some sort that will determine which shell to use to run rvm based upon what is available. Anyway, it does seem like the default version of bash that comes from apple is abnormally bad.