TL;DR - use the bootpath, this is the easiest win

On Mon, Jun 17, 2013 at 9:28 AM, Jim Purbrick <> wrote:
On 4 June 2013 14:22, Walter Chang <> wrote:
> Most of jython's startup overhead comes from:
> -jvm startup
> Did you try starting the jvm in client mode?

Yes: my test command ran slightly slower (32s vs 30s in server mode)

> -initial caching of jars in your classpath bootpath
> pruning your classpath does help a bit on initial runs.

How do I do this and still have java find the jars when it needs them?
Currently I have 28 jars passed to java via "-classpath".

Use -Xbootclasspath/a as an alternative to -classpath for those jars (FWIW, I'd recommend looking at the jython script for this and other similar environmental setup). This is probably the  easiest way to get a significant win on Jython startup performance by avoiding the overhead of class verification.


$ time jython27 -c "print 42"

real 0m1.363s
user 0m1.976s
sys 0m0.150s


$ time jython27 --boot -c "print 42"

real 0m0.919s
user 0m1.212s
sys 0m0.115s

(jython27 is my alias to the jython script running against Jython trunk; lastly all numbers are reported from my laptop... differences are certainly significant and stable)

> -try the openjdk 8 jigsaw preview releases
> this will allow you to shrink your jvm somewhat.  Note that openjdk hotspot
> is slower than the oracle version.

I'd like to avoid jdk specific optimizations if possible.

> -jvm startup memory options
> a big heap slows the startup of the jre.  Small builds probably can start
> with less memory

I tried passing -Xmx600m, -Xmx300m and -Xmx128m to java and saw nearly
identical run times compared with the default -Xmx1000m (but
significantly lower memory usage)

Are there any other options I can try? Would using the
PythonInterpreter API and/or PyObjects APIs instead of JSR-223 help?

JSR223 support and PythonInterpreter implement similar facades to the Jython runtime, therefore I would not expect even observable performance differences.
Could I prune Python libraries that aren't used out of Jython to
improve performance?

The closest to this is -S (don't import site, and those dependencies) in the jython startup script, however this path is not used by JSR223/PythonInterpreter. Savings of ~250 ms in my testing:

$ time jython27 --boot -S -c "print 42"

real 0m0.673s
user 0m0.861s
sys 0m0.093s

- Jim