Those Small Documents Throughput metrices in YCSB develop and Windows jobs got obvious (~10%) degradation since the builds on Nov 29. 

http://build.wiredtiger.com:8080/job/mongodb-perf-ycsb-develop/1544/

http://build.wiredtiger.com:8080/job/mongodb-perf-ycsb-windows/1372/ 

The list of WT tickets included in the issue builds: 

1. WT-4421 Add a way to calculate modify operations. (#4353) (commit: 4e2c760) (detail / githubweb)
2. WT-4421 Exclude wiredtiger_calc_modify from the Java API. (#4379) (commit: 3d31e0d) (detail / githubweb)
3. WT-4434 Modify zstd compression level from 3 to 6 (#4380) (commit: 703d6a6) (detail / githubweb)
4. WT-4421 Extend modify test to also use new calculate modify API (#4381) (commit: 997b717) (detail / githubweb)
5. Ignore #define HAVE_ATTACH, it's not useful and breaks in testing. (commit: 65e17a8) (detail / githubweb)
6. WT-4433 Enable dynamic compression for snappy (#4382) (commit: 3b6a6e2) (detail / githubweb)
7. The byte string may not match the format (it happens if a formatted, (commit: 3261a0a) (detail / githubweb)

Please note some metrics in wiredtiger-perf-long job had an obvious bump for the build on the same day:

http://build.wiredtiger.com:8080/job/wiredtiger-perf-long/414/