I was analyzing some performance data from a YCSB workload and noticed the following callstack taking non-trivial time during reconciliation.

__wt_block_manager_named_size
__hs_insert_updates
__rec_write_wraup
__wt_reconcile
__wt_evict

That corresponds to this check related to allowing a maximum history store size to be defined (which is an optional configuration option history_store=(file_max)) - a quick skim of current MongoDB indicates that they don't use the configuration option.

It should be easy to change the code so that it only retrieves the file size if history store size enforcement is in place.