On DAG team, we recently wrapped up the Targeted Test Selection project. As part of the investigation into whether selected_tests patch builds were running in < 1 hour (one of the goals of the project), I noticed that compile was consistently taking ~40 minutes on the patch builds I looked at (examples below).

My understanding is that compile on patch builds should run in about ~20 minutes, so I thought it might be worth making a ticket about. There were a few patch builds that compiled in ~20 mins so I was wondering what the compile time difference is caused by.

All selected_tests patch builds in past week:

• https://evergreen.mongodb.com/version/5e8b4c0c3e8e862de2c17084 - compiled in 44 mins
• https://evergreen.mongodb.com/version/5e8b5b0e0ae6061ba61b4fc0 - compiled in 44 mins
• https://evergreen.mongodb.com/version/5e8787a6d6d80a583e3b39ed - compiled in 44 mins
• https://evergreen.mongodb.com/version/5e8761e057e85a1febcafdf4 - compiled in 45 mins
• https://evergreen.mongodb.com/version/5e8676bb3627e001aa726295 - compiled in 20 mins
• https://evergreen.mongodb.com/version/5e8561153627e07113ecb472 - compiled in 44 mins
• https://evergreen.mongodb.com/version/5e84f8531e2d171a6d5ef9ee - compiled in 21 mins
• https://evergreen.mongodb.com/version/5e8387f10ae606330e32347d - compiled in 43 mins