Final answer:
If the working set window is too large, it may overlap several localities, leading to reduced efficiency and potentially impacting the performance due to unnecessary page faults and evictions.
Step-by-step explanation:
When dealing with the concept of a working set window in the context of operating systems, the size of the working set is essential for optimal performance. If the working set window is too large, it may overlap several localities. This means that the set of pages in memory would be larger than necessary for the current execution context, potentially storing pages that are not being referenced in the immediate locality. As a result, the system might keep unnecessary pages in memory, leading to reduced efficiency because it could evict pages that are more likely to be accessed in the near future or cause unnecessary page faults when it has to bring in pages that have been evicted prematurely.