WiredTiger tracks specific spin locks and read-write locks that possibly take a longer time. One of the spinlock schema and read-write lock dhandle is also tracked in the session statistics also.

During the initialization of the lock track, the session statistic offset variable is initialized to 0 and it will be properly set only to the schema and dhandle locks. For the rest of the locks, that variable is assigned a default value of 0.

For other spin locks and read-write locks that are tracked only in the connection will increment the bytes read value of the session stats due to the default value being 0.

The solution to this problem is to initialize the stat_session_usecs_off to -1 and check its value before incrementing the session stats.