WT-16707 aims to add a checkpoint fast path by writing page deltas without full reconciliation in DSC. The motivation being that the majority of the overhead for checkpoints is in reconciliation, and frequent checkpoints in DSC is one of the causes for low performance in bulk-load workloads. Existing checkpoint stats don’t tell us how much time is spent in the reconciliation subphrases, i.e. how much time is attributable to page walk, constructing, write I/O etc. By adding some statistics we can quantify the potential savings from a delta fast path and attribute the checkpoint/reconciliation performance work in DSC.
 
We can track statistics for time spent in: 

• Preparation (start txn, collect dhandles / schema lock).
• Handle walk (iterating the dhandle list).
• B-tree walk + construct (per-page reconciliation work).
• Write (time spent issuing writes for full images and deltas).