Improving startup time of Clojure REPL with Leiningen on the Raspberry Pi

Question

I got a Rasperry Pi 512 MB version (late 2012) and installed the Developer Preview of Java SE 8 for ARM on it. When I create a new Clojure project with Leiningen and launch the nREPL by doing lein repl it takes a bit more than two minutes (roughly 130 - 140 seconds) until the REPL has been initialized and can be used.

When launching the JAR file directly java -jar clojure-1.4.0/clojure-1.4.0 the REPL starts up in 25s.

I'm using fast class 10 SD cards (SanDisk Extreme with up to 30 MB/s). How come that the difference between using Leiningen with nRepl vs launching the JAR file is so big? What could be done to improve the startup time with Leiningen for the Raspberry Pi?

Butchery

lein repl checks dependencies, builds the project and prepares auto completion and other shenanigans like that. You could try to do clever things like keeping a JVM with Clojure loaded to run leiningen on around, but I'm not sure how much that would actually reduce the startup time. I suppose ideally, you should just try to not run lein repl very often. – Campman

Yes, that's what I've been thinking as well. I've seen similar discussions on the Clojure mailing list, but on a desktop PC or notebook the slowdown is not as bad as it is on the Raspberry Pi. Common Lisp REPL starts up in 1s, the performance overhead for Java and classpath scanning is pretty heavy. Not sure if Clojure is such a good development platform for embedded devices. – Butchery

raju-bitter, I'm curious of what Common-Lisp implementation are you using in the Pi... – Betroth

GNU CLISP 2.49 (2010-07-07), it's in the repository for Wheezy. Just did a sudo apt-get install clisp. – Butchery

This seems to explain some of it nicholaskariniemi.github.io/2014/02/25/… – Suitable

See also dev.clojure.org/display/design/Improving+Clojure+Start+Time – Willhite

Answer 1

Also try grenchman: Fast invocation of Clojure code over nREPL.

Cami

Answer 2

You can try drip which wraps the java command and prepare a fresh jvm waiting in the background.

Druce

Thanks, I'll try that and report the results here. – Butchery

Answer 3

It seems the slow startup of clojure in general is the loading of core and various other things discussed here:

http://blog.ndk.io/solving-clojure-boot-time.html

Suitable

Answer 4

Actually the Leiningen starts in it's own JVM and then nests the project's vm inside it.
Then it checks deps, figures out the changes and so on.

You can avoid vm nesting with the trampoline task of lein like so:
lein trampoline repl

But this command requires the lein to be called in a project directory

Joesphjoete