When the faculty member clicks on the gradebook it's somewhat slow to load, unless editing is on and then the performance is markedly worse. In Chrome and Safari, it's essentially unusable, often leaving Chrome unresponsive. Using the browers' development tools, we've determined that a significant amount of time (90% or more - more than 98% with Chrome) is being spent in page render operations, not downloading data / scripting, and the render behavior seems to occur in phrases (perhaps as each member course's students are added to the list). A standalone (non-meta) class with a similar number of students doesn't have the same issue.
With some testing we have discovered that the performance is noticeably improved when using a non-webkit browser such as Firefox or Microsoft Edge, or by changing the Boost theme to the Clean theme. Even though using Firefox has made the gradebook usable the performace is still not ideal and not all faculty use Firefox for browsing.
We've largely ruled-out a server-side performance issue due to the differences between browsers - on the same client computer, Edge can display the edit screen for the course gradebook in under 20 seconds, while Chrome took over 300. The data seems to be coming back from the server fairly quickly. We're not seeing any load on either the front-end moodle server or on the database server. We're almost left wondering if, for each course being included, there's an additional render and re-render of the courses already queried as the list is being built.
Has anyone ran into the same problem? We are looking for any suggestions of improvement.