How to Improve Jruby Load Time

How to improve jRuby load time?

There are a couple of things you could try:

• use the very latest and greatest version of JRuby (due to the extensive testsuites, even the bleeding edge git master branch is usually pretty stable), they are constantly working on startup time
• choose your JVM wisely, Oracle JRockit for example is geared towards servers and thus startup performance is not a concern (those apps are only restarted once every couple of years anyway), Sun has mainly neglected the desktop for the last ten years or so, but has gotten consistently better since 1.6u12 (try the recently released 1.6u18) and also in 1.7. IBM's J9 is also said to be pretty lightweight.
• try nailgun, which is a project that keeps a JVM running as a daemon in the background (there is builtin support in JRuby, try running your scripts with jruby --ng)
• just don't use JRuby for unit tests and rake tasks: the ThoughtWorks Mingle team, for example uses MRI for unit tests, rake tasks and development and JRuby for integration tests, regression tests and production. (This obviously only works if you don't use any Java libraries in your rake tasks and tests.)

However, tests and scripts are the worst case scenario for JRuby. The JRuby runtime alone is already pretty heavy, much heavier than MRI. Just loading the entire beast from disk into RAM can already take longer than running the same script in MRI. And we haven't even added the startup time for the JVM yet!

rspec tests under jruby on Windows running very slow

It is not loading RSpec, but it is JVM startup time you are feeling.

See https://github.com/jruby/jruby/wiki/Improving-startup-time for more information.

How to improve jRuby load time?

There are a couple of things you could try:

• use the very latest and greatest version of JRuby (due to the extensive testsuites, even the bleeding edge git master branch is usually pretty stable), they are constantly working on startup time
• choose your JVM wisely, Oracle JRockit for example is geared towards servers and thus startup performance is not a concern (those apps are only restarted once every couple of years anyway), Sun has mainly neglected the desktop for the last ten years or so, but has gotten consistently better since 1.6u12 (try the recently released 1.6u18) and also in 1.7. IBM's J9 is also said to be pretty lightweight.
• try nailgun, which is a project that keeps a JVM running as a daemon in the background (there is builtin support in JRuby, try running your scripts with jruby --ng)
• just don't use JRuby for unit tests and rake tasks: the ThoughtWorks Mingle team, for example uses MRI for unit tests, rake tasks and development and JRuby for integration tests, regression tests and production. (This obviously only works if you don't use any Java libraries in your rake tasks and tests.)

However, tests and scripts are the worst case scenario for JRuby. The JRuby runtime alone is already pretty heavy, much heavier than MRI. Just loading the entire beast from disk into RAM can already take longer than running the same script in MRI. And we haven't even added the startup time for the JVM yet!

Any way to boost JVM Startup Speed?

Try Nailgun.

Note: I don't use it personally.

Time limit the execution of user code (JRuby)

Not sure how you're embedding the Ruby code, but you could easily have a background timer thread that evaluates

raise YourTimeLimitExceededException, 'no more time'

after a period of time. You'd also want to disable Thread.new and Thread.start (as well as java.lang.Thread.new) for the user code, or they could easily circumvent your timer.

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