wall clock time การใช้

Depending on the application its definition can take into account the difference between wall clock time and the CPU time.
The extra pass over the list is a linear time operation, so while this technique requires more wall clock time, the asymptotics are not any worse.
However, it sounded like you were ( understandably ) more concerned about the number of hard drive accesses than the amount of wall clock time that went past.
In contrast, elapsed real time ( or simply real time, or wall clock time ) is the time taken from the start of a computer program until the end as measured by an ordinary clock.