Before upgrading our MongoDB cluster version from 4.4.29 to 6.0.14,  we did some ycsb benchmarking to this two versions.  Benchmak result shows that under mixed read/write and pure insert workloads,  MongoDB 6.0.14 suffers a 15% performance drop compared to 4.4.29, currenty we cannot find out  the reason for such a high performance drop, so it will be very helpful if MongoDB Team can help us figure it out. Thanks.

Following is one of our benchmarking details under ycsb pure insert workloads:

• System Environments:

               Operating System: Debian 10.13

               CPU:  Intel(R) Xeon(R) Silver 4214R CPU @ 2.40GHz(6 cores)

               Memory: 50 GB

               Disk:  1.92 TB SSD S4500

• Benchmark Result: 4.4.29 27705 ops vs 6.0.14  23700 ops(attchment 1.png and 2.png)

• WiredTiger Perf Stats:  db.serverStatus().wiredTiger.perf shows that 6.0.14 has 10% insert ops with write latency greater than 100 us, while 4.4.29 only has 5% of insert ops(total 1,0000,0000 ops)(attachment 6.0.14_perf.png and 4.4.29_perf.png){}
• mongod Perf Stats:  linux-perf of mongod shows that mongod under 4.4.29 spends about 6.8% more in performInserts call, but code changes a lot from 4.4.29 to 6.0.14, and we cannot find out a main reason to explain the drop(attachment mongod_6.0.14_perf.png and mongod_4.4.29_perf.png)