Why is any Java/Clojure program slowed down when run from Leiningen? -


while benchmarking clojure app , trying pin down performance problems, noticed peculiar behavior: when entire program written in java, when launched leiningen seems experience significant slowdown.

say have java program:

public class foo {     public static void main(string[] args) throws exception {         (int = 0; < 10; i++)              run();     }      public static void run() {         final long start = system.nanotime();          random r = new random();         double x = 0;         for(int i=0; i<50000000; i++)             x += r.nextdouble();          final long time = timeunit.milliseconds.convert(system.nanotime() - start, timeunit.nanoseconds);         system.out.println("time (ms): " + time + " total: " + x);     } }

when run program, execution times (per run) of 1s. however, when run leiningen so:

lein run -m foo

i run times of 2s! how clojure/leiningen manage slow down complete java program much? doing wrong?

i've tried examining system properties in both runs , couldn't find glaring (like different jit settings). in both cases use java 7 server compiler.

edit: don't know why question has been downvoted. i'm not against clojure. on contrary, love clojure , i'm going use it. have serious performance problem absolutely must solve.

update: running lein trampoline solves issue! (though have no idea why) i've updated question reflect indeed leiningen issue, not clojure issue.

another update: happens clojure code well. running without trampoline slows down code 5x.

it's due different jit behaviour.

the performance of jit compiled can affected number of things, including:

  • what startup code gets called, affect jit statistics
  • what other classes have been loaded (e.g. other subclasses of random) affect compiler's optimisation of method call dispatch

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