Right now we have a project-level "batchtime" set to 0 in the Evergreen "WiredTiger (develop)" project, which means by default all build variants would get scheduled for each commit unless there's a different build-variant-level "batchtime" setting (which overwrites the project-level setting). As PPC, zSeries, and macOS all have limited building resources, to reduce pressure on those Evergreen distro pools, we could run our corresponding build variants less frequently (once every a few commits) by setting a non-zero build-variant-level "batchtime".

In order to keep test failure triaging easy, we should also turn on the stepback feature for the concerned build variants, so that the Evergreen system could automatically schedule the same task in the previous commit build in case of a task failure, saving the manual efforts to pinpoint the offending commit for the given failing task.