Recent work has shown that changes in performance (specifically, page load times), can have dramatic effects on user engagement[citation needed]. Recently, the platform team at the Wikimedia Foundation has experimented with deployments of HipHop Virtual Machine (HHVM) a new execution engine for PHP that promises substantial improvements in page load times. This benefit is especially noticeable in the case of logged-in editors since their page loads are generally not served by the varnish caching servers -- and therefore have to be computed upon request. Performance analysis suggests that pages generally load FIXME% faster.

We hypothesize that the type of performance improvement that HHVM provides will result in improved engagement of editors in Wikipedia. In this study we'll specifically focus on new editor engagement.

See results here: https://meta.wikimedia.org/wiki/Research:HHVM_newcomer_engagement_experiment