Many-collection-test was run with 250k collections on 5.0 (a2872f2494) and 4.4 (https://github.com/mongodb/mongo/commit/7c6b85895f) to write a report on improvements made, WT-7614. We found that 5.0 showed extended stalls that did not necessarily relate to the checkpoint (There might be a relationship since we see longer checkpoints during the same time). These were not observed with 4.4. We should investigate the reasons behind the stalls on 5.0, and possibly fix them.

For instance A-B and C-D:

zooming in on C-D: