We started to see obvious degradation (~12%) on small document throughput performance metric on mongodb-perf-ycsb-windows job since build 1425. The previous build 1424 failed and should not be excluded from the cause candidate list. The YCSB Linux job mongodb-perf-ycsb-develop also had degradation, but not as obvious as the YCSB Windows job.  

The combined list of WT tickets (from build 1424 and 1425) that could potentially caused the degradation is listed below:

• The WiredTiger LSM chunk drop code doesn't acquire a readlock on the (commit: 7417222) (detail / githubweb)
• WT-4447 Add subsystem I/O throttling ability. (#4408) (commit: 7f97a5f) (detail / githubweb)
• WT-4369 random_directio shouldn't assume child threads wrote any data (commit: fc4c54a) (detail / githubweb)
• WT-4489 Store correct timestamp in cells on disk (#4433) (commit: 4ff2dfe) (detail / githubweb)
• WT-4053 Add statistic for data handle size (#4451) (commit: 2e2b128) (detail / githubweb)
• WT-4433 Enable dynamic compression for snappy (#4457) (commit: 0520ff2) (detail / githubweb)
• WT-4501 Fix a race condition opening/closing the shared cache (#4453) (commit: c26ef4c) (detail / githubweb)
• WT-4557 Remove error_prefix from base configuration file, set (commit: 8af2293) (detail / githubweb)
• WT-4533 Upgrade to v3 toolchain for Evergreen tests (#4461) (commit: 94636c1) (detail / githubweb)