Why is BeanShell slower than JSR223 with Groovy in JMeter?

JSR223 script engines, including the Groovy engine commonly paired with JSR223 elements in JMeter, generally compile a script once and cache that compiled form for reuse across subsequent executions, so repeated iterations of the same script don't pay a full parsing-and-interpretation cost every single time.

BeanShell, by default, re-parses and interprets the script fresh on each execution rather than caching a compiled form the same way, so at high iteration counts, that repeated interpretation overhead compounds into a measurable performance difference compared to JSR223's cached-compilation approach.

This is the core reason official JMeter guidance and most current best practice recommends JSR223 with Groovy over BeanShell for new scripting needs, treating BeanShell as adequate for occasional, low-volume scripting but a poor choice specifically for scripts that run on every iteration of a high-thread-count load test.

Invest now in Acorns!!! 🚀
Join Acorns and get your $5 bonus!

Acorns is a micro-investing app that automatically invests your "spare change" from daily purchases into diversified, expert-built portfolios of ETFs. It is designed for beginners, allowing you to start investing with as little as $5. The service automates saving and investing. Disclosure: I may receive a referral bonus.

Invest now!!! Get Free equity stock (US, UK only)!

Use Robinhood app to invest in stocks. It is safe and secure. Use the Referral link to claim your free stock when you sign up!.

The Robinhood app makes it easy to trade stocks, crypto and more.

Webull! Receive free stock by signing up using the link: Webull signup.